Shigella

Antimicrob Agents Chemother, 2003 Mar, 47(3), 1137 - 9
In vitro susceptibilities of Shigella flexneri and Streptococcus pyogenes to inner gel of Aloe barbadensis Miller; Ferro VA et al.; Aloe barbadensis Miller (or Aloe vera) has widespread use in health products, and despite numerous reports on the whole plant, little work has been performed on the inner gel, which has been used extensively in these products . This report describes the in vitro susceptibilities of two bacteria to this component.

Infect Immun, 2003 Mar, 71(3), 1551 - 6
Effects of ectopically expressed neuronal Wiskott-Aldrich syndrome protein domains on Rickettsia rickettsii actin-based motility; Harlander RS et al.; Neuronal Wiskott-Aldrich syndrome protein (N-WASP) and the actin-related protein 2/3 (Arp2/3) complex have emerged as critical host proteins that regulate pathogen actin-based motility . Actin tail formation and motility in Listeria monocytogenes require the Arp2/3 complex but bypasses N-WASP signaling . Motility of Shigella flexneri and vaccinia virus requires both N-WASP and the Arp2/3 complex . Functional roles for these cytoskeletal regulatory proteins in actin-based motility of Rickettsia rickettsii have not been established . In this study, functional domains of N-WASP tagged with green fluorescent protein that have characterized effects on Shigella and vaccinia virus actin-based motility were ectopically expressed in HeLa cells infected with R . rickettsii to assess their effects on rickettsial motility . S . flexneri-infected cells were used as a control . Expressed N-WASP domains did not localize to R . rickettsii or their actin tails . Expression of N-WASP missing the VCA domain (for "verprolin homology, cofilin homology, and acidic domains"), which acts as a dominant-negative form of N-WASP, completely inhibited actin-based motility of S . flexneri while only moderately inhibiting motility of R . rickettsii . Similarly, expression of the VCA domain, which acts as a dominant-negative with respect to Arp2/3 complex function, severely inhibited actin-based motility of S . flexneri (no motility observed in the majority of expressing cells) but only moderately inhibited R . rickettsii motility . These results, taken together with the differential effects on motility observed upon expression of other N-WASP domains, suggest that actin-based motility of R . rickettsii is independent of N-WASP and the Arp2/3 complex.

Infect Immun, 2003 Mar, 71(3), 1352 - 60
Genetic characterization and immunogenicity of coli surface antigen 4 from enterotoxigenic Escherichia coli when it is expressed in a Shigella live-vector strain; Altboum Z et al.; The genes that encode the enterotoxigenic Escherichia coli (ETEC) CS4 fimbriae, csaA, -B, -C, -E, and -D', were isolated from strain E11881A . The csa operon encodes a 17-kDa major fimbrial subunit (CsaB), a 40-kDa tip-associated protein (CsaE), a 27-kDa chaperone-like protein (CsaA), a 97-kDa usher-like protein (CsaC), and a deleted regulatory protein (CsaD') . The predicted amino acid sequences of the CS4 proteins are highly homologous to structural and assembly proteins of other ETEC fimbriae, including CS1 and CS2, and to CFA/I in particular . The csaA, -B, -C, -E operon was cloned on a stabilized plasmid downstream from an osomotically regulated ompC promoter . pGA2-CS4 directs production of CS4 fimbriae in both E . coli DH5alpha and Shigella flexneri 2a vaccine strain CVD 1204, as detected by Western blot analysis and bacterial agglutination with anti-CS4 immune sera . Electron-microscopic examination of Shigella expressing CS4 confirmed the presence of fimbriae on the bacterial surface . Guinea pigs immunized with CVD 1204(pGA2-CS4) showed serum and mucosal antibody responses to both the Shigella vector and the ETEC fimbria CS4 . Among the seven most prevalent fimbrial antigens of human ETEC, CS4 is the last to be cloned and sequenced . These findings pave the way for CS4 to be included in multivalent ETEC vaccines, including an attenuated Shigella live-vector-based ETEC vaccine.

Infect Immun, 2003 Mar, 71(3), 1255 - 64
Structural characterization of the N terminus of IpaC from Shigella flexneri; Harrington AT et al.; The primary effector for Shigella invasion of epithelial cells is IpaC, which is secreted via a type III secretion system . We recently reported that the IpaC N terminus is required for type III secretion and possibly other functions . In this study, mutagenesis was used to identify an N-terminal secretion signal and to determine the functional importance of the rest of the IpaC N terminus . The 15 N-terminal amino acids target IpaC for secretion by Shigella flexneri, and placing additional amino acids at the N terminus does not interfere with IpaC secretion . Furthermore, amino acid sequences with no relationship to the native IpaC secretion signal can also direct its secretion . Deletions introduced beyond amino acid 20 have no effect on secretion and do not adversely affect IpaC function in vivo until they extend beyond residue 50, at which point invasion function is completely eliminated . Deletions introduced at amino acid 100 and extending toward the N terminus reduce IpaC's invasion function but do not eliminate it until they extend to the N-terminal side of residue 80, indicating that a region from amino acid 50 to 80 is critical for IpaC invasion function . To explore this further, the ability of an IpaC N-terminal peptide to associate in vitro with its translocon partner IpaB and its chaperone IpgC was studied . The N-terminal peptide binds tightly to IpaB, but the IpaC central hydrophobic region also appears to participate in this binding . The N-terminal peptide also associates with the chaperone IpgC and IpaB is competitive for this interaction . Based on additional biophysical data, we propose that a region between amino acids 50 and 80 is required for chaperone binding, and that the IpaB binding domain is located downstream from, and possibly overlapping, this region . From these data, we propose that the secretion signal, chaperone binding region, and IpaB binding domain are located at the IpaC N terminus and are essential for presentation of IpaC to host cells during bacterial entry; however, IpaC effector activity may be located elsewhere.

J Biol Chem, 2003 May 9, 278(19), 17103 - 7 Epub 2003 Feb 05.
Helical structure of the needle of the type III secretion system of Shigella flexneri; Cordes FS et al.; Gram-negative bacteria commonly interact with animal and plant hosts using type III secretion systems (TTSSs) for translocation of proteins into eukaryotic cells during infection . 10 of the 25 TTSS-encoding genes are homologous to components of the bacterial flagellar basal body, which the TTSS needle complex morphologically resembles . This indicates a common ancestry, although no TTSS sequence homologues for the genes encoding the flagellum are found . We here present an approximately 16-A structure of the central component, the needle, of the TTSS . Although the needle subunit is significantly smaller and shares no sequence homology with the flagellar hook and filament, it shares a common helical architecture ( approximately 5.6 subunits/turn, 24-A helical pitch) . This common architecture implies that there will be further mechanistic analogies in the functioning of these two bacterial systems.

Semin Nephrol, 2003 Jan, 23(1), 88 - 106
Pathology of renal diseases in the tropics; Boonpucknavig V et al.; Renal diseases unique to the tropics are those that occur in association with infectious diseases including dengue hemorrhagic fever, typhoid fever, shigellosis, leptospirosis, lepromatous leprosy, malaria, opisthorchiasis, and schistosomiasis . These renal complications can be classified on the basis of their clinical and pathologic characteristics into acute transient reversible glomerulonephritis, chronic progressive irreversible glomerulonephritis, amyloidosis, and acute renal failure (ARF) resulting from acute tubular necrosis, acute tubulointerstitial nephritis, and thrombotic microangiopathy . Certain primary glomerular diseases including immunoglobulin (Ig) M nephropathy and focal segmental and global glomerulosclerosis are prevalent in some tropical countries . Renal complications of venomous snakebites also are common in the tropics . This article discusses and summarizes important works in the literature in respect to the clinical syndromes, pathologic features, and pathogenesis of tropical renal diseases both in humans and experimental animal models .

J Antimicrob Chemother, 2003 Feb, 51(2), 427 - 9
Growing antimicrobial resistance of Shigella isolates; Ashkenazi S et al.; Appropriate antibiotic treatment of shigellosis depends on identifying resistance patterns . By studying Shigella isolates in central Israel from 1998 to 2000, and comparing with the period 1991-1992, we identified a significantly increased resistance to tetracycline (from 23% to 87%, P < 0.00001), high resistance to trimethoprim-sulfamethoxazole (94%) and ampicillin (85%) and emerging resistance to quinolones (0.5-2%) . These data mandate local monitoring of resistance and its consideration in empirical therapy.

Epidemiol Infect, 2002 Dec, 129(3), 445 - 50
Use of AFLP, plasmid typing and phenotyping in a comparative study to assess genetic diversity of Shigella flexneri strains; Herrera S et al.; Shigella flexneri infections are one of the main causes of acute diarrhoea in Cuba . Twenty strains isolated from sporadic cases in nine different Cuban provinces were characterized . Serotyping, antibiotic-resistance typing, plasmid-typing and AFLP-typing were used to determine their suitability for use in epidemiological studies of S . flexneri . The predominant serotypes were serotype 6 (35%) and serotype 2 (35%) . Eleven different plasmid profiles were detected (Diversity Index = 0.92) . AFLP-typing discriminated 12 different patterns (DI = 0.95), these patterns were not coincident with plasmid-typing patterns . Both techniques combined distinguished 14 patterns among the 20 studied strains (DI = 0.99) . There was no consistent relationship between plasmid-typing and AFLP-typing patterns or antibiotic-resistance typing patterns . Ninety-five percent of S . flexneri strains were multiresistant.

Antimicrob Agents Chemother, 2003 Feb, 47(2), 727 - 34
Molecular epidemiology of the SRL pathogenicity island; Turner SA et al.; The Shigella resistance locus (SRL), which is carried on the SRL pathogenicity island (PAI) in Shigella flexneri 2a YSH6000, mediates resistance to the antibiotics streptomycin, ampicillin, chloramphenicol, and tetracycline . In the present study, we investigated the distribution and structural variation of the SRL and the SRL PAI in 71 Shigella isolates and 28 other enteric pathogens by PCR and Southern analysis . The SRL and SRL-related loci, although absent from the other enteric pathogens evaluated in this study, were found to be present in a number of Shigella isolates . SRL PAI markers were also present in the majority of strains carrying the SRL and SRL-related loci . PCR linkage studies with six of these strains demonstrated that the SRL is carried on elements similar in structure and organization to the YSH6000 SRL PAI, consistent with the hypothesis that the SRL PAI may be involved in the spread of multiple-antibiotic resistance in these strains.

Bioorg Med Chem, 2003 Mar 6, 11(5), 781 - 8
Rational design and synthesis of peptide ligands for an anti-carbohydrate antibody and their immunochemical characterization; Johnson MA et al.; Molecular mimics of carbohydrates present an alternative source of compounds to target pathways involving protein-carbohydrate interactions . Certain peptides act as molecular mimics of carbohydrates in binding to anti-carbohydrate antibodies . A series of potential peptide ligands for the anti-carbohydrate antibody SYA/J6, directed against Shigella flexneri Y, was designed by molecular modeling based on a crystal structure of the antibody complex with a carbohydrate-mimetic peptide . These octapeptides were synthesized using solid-phase peptide synthesis, and their recognition by the antibody was investigated . The results shed light on the nature of peptide-carbohydrate mimicry.

Mol Microbiol, 2003 Feb, 47(3), 825 - 38
An extended role for the nucleoid structuring protein H-NS in the virulence gene regulatory cascade of Shigella flexneri; Beloin C et al.; The H-NS nucleoid structuring protein has been shown previously to play a negative role in controlling virulence gene expression in Shigella flexneri by repressing transcription of the virF and virB regulatory genes and the VirF-dependent icsA structural gene under non-permissive growth conditions . Here, we show that H-NS also acts at the promoters of the VirB-dependent structural genes in the regulatory cascade . H-NS protein binds to the promoter regions in vivo and in vitro . The promoters were shown physically and by in silico analysis to contain regions of DNA curvature, a feature of H-NS binding sites . H-NS binding sites were determined by DNase I footprinting at the icsB and the virA promoters . The locations of these sites were consistent with a role for H-NS as a transcription repressor . The VirB-dependent structural gene promoters were found to respond directly to the H-NS repressor, revealing a level of control that is additional to that exerted by the H-NS-dependent virB activator gene . Moreover, the promoters were sensitive to the level of VirB protein in the cell, requiring a threshold level of VirB to be reached before becoming active . A model is discussed in which the levels of expression of the structural genes reflect the outcome of competition between the countervailing regulatory activities of the H-NS and VirB proteins.

Vaccine, 2003 Jan 17, 21(5-6), 333 - 40
Immune responses elicited against multiple enterotoxigenic Escherichia coli fimbriae and mutant LT expressed in attenuated Shigella vaccine strains; Barry EM et al.; Shigella and enterotoxigenic Escherichia coli (ETEC) continue to be important causes of diarrheal disease in infants and young children in developing countries and are major etiologic agents of traveler's diarrhea . Since attenuated strains of Shigella have been developed as live oral vaccines against shigellosis, we have adapted these attenuated Shigella strains to serve as carriers of ETEC antigens, thereby constituting a hybrid vaccine . Since protective immunity against ETEC is largely directed against fimbrial antigens (of which there are multiple antigenic types), we have individually expressed four different ETEC fimbriae, including CFA/I, CS2, CS3, and CS4, using deltaguaBA attenuated Shigella vaccine strain CVD 1204 as a prototype live vector . Following mucosal (intranasal) immunization of guinea pigs, serum IgG and mucosal IgA responses were elicited against each fimbrial type . An additional strain was constructed expressing a detoxified version of the human ETEC variant of heat labile toxin (LThK63) . Following mucosal immunization of guinea pigs with a mixed inoculum containing five Shigella strains each expressing a different ETEC antigen, immune responses were observed against each ETEC antigen plus the Shigella vector.

Vaccine, 2003 Jan 30, 21(7-8), 644 - 8
Immunogenicity of an HIV-1 gag DNA vaccine carried by attenuated Shigella; Xu F et al.; The use of live attenuated invasive bacteria as a carrier for DNA-based vaccines has been reported recently . In this study, we used a Shigella flexneri serotype 2a rfbF mutant for immunization of a DNA vaccine coding for HIV-1 SF2 Gag . The recombinant bacterial vector delivered gag DNA to mammalian cells in vitro resulting in Gag protein expression, and was found to have a low level of pathogenicity among a number of Shigella cell spread defective mutants tested . Intranasal immunization of mice with live recombinant bacterial cells induced a gag-specific cellular immune response similar to that seen with i.m . injection of naked DNA . Importantly, a strong boosting effect was observed in mice primed with DNA, suggesting utility of bacterial vectors in prime-boost vaccination regimens.

Eur J Clin Microbiol Infect Dis, 2002 Dec, 21(12), 887 - 9 Epub 2002 Dec 10.
Retrospective analysis of the first clonal outbreak of nalidixic acid-resistant Shigella sonnei shigellosis in Israel; Dagan D et al.; Reported here is a retrospective molecular analysis of the isolates recovered from the first outbreak of nalidixic acid (NA)-resistant Shigella sonnei shigellosis to occur in Israel . The outbreak affected 94 children . In the retrospective analysis, a total of 13 NA-resistant isolates and five NA-susceptible isolates recovered during the outbreak period were examined . Restriction fragment length polymorphism profiles obtained by digestion with BamHI, PvuI, HinfI or SmaI yielded identical profiles for all 18 isolates . All NA-resistant strains had an identical plasmid profile, but this profile differed from that displayed by the susceptible strains . In all of the NA-resistant strains a 304 bp fragment in the gyrA gene coding for a region associated with NA resistance was sequenced and showed a single point mutation, Ser83-->Phe . In this outbreak, the isolates of NA-resistant Shigella sonnei belonged to a single clone and NA resistance was associated with a point mutation in the gyrA gene.

Clin Microbiol Infect, 2002 Dec, 8(12), 803 - 5
Pyosalpinx: not always a sexual transmitted disease? Pyosalpinx caused by Plesiomonas shigelloides in an immunocompetent host; Roth T et al.; Plesiomonas shigelloides are ubiquitous Gram-negative bacteria that are found in fresh or marine water, particularly in tropical or warm climates; they were recently implicated in diarrhoeal disease . Patients usually present with a history of recent travel to tropical regions or consumption of uncooked seafood . Extraintestinal disease has rarely been reported, occurring generally in neonates or immunocompromised patients, and is often fatal . We report a case of right pyosalpinx due to P . shigelloides acquired by swimming in contaminated water . Laparoscopic salpingectomy led to a good outcome.

Mol Microbiol, 2003 Jan, 47(2), 519 - 27
Putrescine or a combination of methionine and arginine restores virulence gene expression in a tRNA modification-deficient mutant of Shigella flexneri: a possible role in adaptation of virulence; Durand JM et al.; The wild-type strain YSH6000 of Shigella flexneri growing in minimal medium contains the modified nucleoside epoxy-Q (oQ) in a subset of tRNAs . This nucleoside is lacking in tRNA from a tgt mutant of this bacterium . When these bacteria are growing in minimal medium, the expression of virulence genes is 10-fold lower in the tgt mutant than in the wild type, although only a twofold reduction in the expression of these virulence factors is observed in broth . Such a strong media-dependant expression of virulence genes was not observed in the wild type . Accordingly, the level of the positive regulator of virulence, VirF, is much lower in the mutant than in the wild type . However, the transcription of the virF gene in minimal medium is the same in the wild type and in the tgt mutant . As the undermodification of tRNA is not affected by the quality of the growth medium, we conclude that such an environmental change in growth conditions partly restores virulence gene expression by counteracting poor translation of the virF mRNA mediated by an oQ-deficient tRNA . Virulence gene expression is partly restored in the tgt mutant by the addition of a mixture of arginine and methionine . Addition of the polyamine putrescine, synthesis of which is metabolically related to that of arginine and methionine, has a comparable stimulatory effect on virulence gene expression . These results not only suggest a role for amino acids and polyamines in the environmental regulation of virulence gene expression in S . flexneri, but also demonstrate a strong and specific involvement of tRNA modifications, and especially oQ, in the adaptation of virulence gene expression to the nutritional quality of the growth medium.

Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao (Shanghai), 2003 Jan, 35(1), 49 - 54
{Simultaneous expression of CS3 colonization factor antigen and LT-B/ST fusion enterotoxin antigen of enterotoxigenic Escherichia coli by attenuated Shigella flexneri 2a}; Liu TT et al.; Enterotoxigenic Escherichia coli (ETEC) causes watery dehydrating diarrhea in infants in developing countries, and is the most common cause of travelers diarrhea . It has been known that the colonazition factor antigens (CFAs) and enterotoxins are important virulence factors of ETEC, and these two kinds of proteins should be included in any effective vaccine against ETEC . In this study, a host-plasmid lethal balancing system was constructed based on asd gene in an avirulent strain of S.flexneri to express CS3 antigens and the fusion LT-B/ST enterotoxins of Escherichia coli . Both of these antigens were expressed steadily in the S . flexneri vector without any antibiotic markers . Antibodies against CS3, LT, ST and LPS of Shigella were detected in sera of mice that were immunized with recombinant bacteria either oragastrically (o.g.) or intranasally (i.n.) . SIgA against CS3 and enterotoxins were detected simultaneously in feces of mice . This work is helpful for constructing multivalent recombinant vaccine for prevention of bacterial diarrhea.

J Clin Microbiol, 2003 Jan, 41(1), 421 - 3
Changes in patterns of antimicrobial susceptibility and integron carriage among Shigella sonnei isolates from southwestern Korea during epidemic periods; Oh JY et al.; Shigella sonnei isolates from southwestern Korea during the epidemic periods of 1998 to 2000 were genetically related . The antimicrobial susceptibilities of the outbreak-related isolates changed annually . All isolates carried class 2 integrons, and the outbreak-related isolates from 1999 also carried class 1 integrons . The antimicrobial susceptibilities of S . sonnei isolates are readily changed by antibiotic selective pressures, and integrons are responsible for resistance to antimicrobial agents commonly used to treat shigellosis.

J Clin Microbiol, 2003 Jan, 41(1), 110 - 7
Phenotypic and genotypic characterization of provisional serotype Shigella flexneri 1c and clonal relationships with 1a and 1b strains isolated in Bangladesh; Talukder KA et al.; The serotypes of 144 strains of Shigella flexneri serotype 1 (serotypes 1a, 1b, and 1c) isolated from patients attending the Dhaka treatment center of the International Centre for Diarrhoeal Disease Research, Bangladesh, between 1997 and 2001 were serologically confirmed by using commercially available antisera and a panel of monoclonal antibodies specific for S . flexneri group and type factor antigen (MASF) . Among serotype 1 isolates, the prevalence of provisional serotype S . flexneri 1c increased from 0 to 56% from 1978 to 2001 in Bangladesh . Detailed biochemical studies revealed that none of the strains of serotype 1 produced indole, while all the strains fermented mannose, mannitol, and trehalose . Twenty percent of the serotype 1c and all the serotype 1a strains fermented maltose and 53% of the serotype 1c strains and 60% of the serotype 1a strains fermented arabinose, whereas all serotype 1b strains were negative for fermentation of these sugars . Only 18% of serotype 1b strains were resistant to nalidixic acid, and most of the serotype 1c and 1b strains were resistant to ampicillin, tetracycline, and trimethoprim-sulfamethoxazole . All the strains of serotypes 1a and 1b and about 88% of the serotype 1c strains were found to be invasive by the Sereny test, had a 140-MDa plasmid, and had Congo red absorption ability . Plasmid profile analysis showed that 26% of the strains of serotype 1 contained identical patterns . Most of the serotype 1c strains (72%) had the 1.6-MDa plasmid, which was not found in either serotype 1a or 1b strains . A self-transmissible middle-range plasmid (35 to 80 MDa) was found in some strains carrying the multiple-antibiotic-resistance gene . Pulsed-field gel electrophoresis analysis yielded three types (types A, B, and C) with numerous subtypes among the serotype 1c strains, whereas serotypes 1b and 1a yielded only one type for each serotype, and those types were related to the types for serotype 1c strains . Ribotyping analysis yielded three patterns for serotype 1c strains and one pattern each for serotype 1a and 1b strains which were similar to the patterns for the serotype 1c strains . Overall analysis of the results concluded that subserotype 1c is closely related to serotypes 1a and 1b . Furthermore, the high rate of prevalence of serotype 1c necessitates the commercial production of antibody against this subserotype to allow the determination of the actual burden of shigellosis caused by provisional serotype 1c.

J Infect Dis, 2003 Jan 1, 187(1), 87 - 95 Epub 2002 Dec 13.
Human lactoferrin impairs virulence of Shigella flexneri; Gomez HF et al.; Lactoferrin is a glycoprotein present in most human mucosal secretions, including human milk . Lactoferrin is bacteriostatic in low iron media and, in some settings, bactericidal . Lactoferrin impairs ability of Shigella flexneri serotype 5 strain M90T to invade HeLa cells . To determine the mechanism by which lactoferrin decreases invasiveness of Shigella organisms, its effect on the major virulence proteins responsible for bacterial uptake by host cells was evaluated . Lactoferrin induced degradation of invasion plasmid antigens IpaB and, to a lesser extent, IpaC, the key proteins responsible for bacteria-directed phagocytosis by mammalian cells . The lipid A-binding N-terminal portion of lactoferrin (residues 1-33) induces release of invasion antigens but does not induce degradation of IpaBC . Lactoferrin does not directly degrade previously released invasion plasmid antigens but works by making IpaBC susceptible to breakdown by surface-expressed protease(s).

Can J Microbiol, 2002 Oct, 48(10), 903 - 10
Phylogenetic study and identification of human pathogenic Vibrio species based on partial hsp60 gene sequences; Kwok AY et al.; The use of hsp60 gene sequences for phylogenetic study and identification of pathogenic marine vibrios was investigated . A 600-bp partial hsp60 gene was amplified by PCR and sequenced from 29 strains representing 15 Vibrio species within the family Vibrionaceae . Sequence comparison of the amplified partial hsp60 gene revealed 71-82% sequence identity among different Vibrio species and 96-100% sequence identity among epidemiologically distinct strains with the same species designation . This degree of discrimination allows unambiguous differentiation of all Vibrio species included in the current study from each other, as well as from Aeromonas hydrophila and Plesiomonas shigelloides, which are often misidentified as Vibrio species by conventional biochemical methods . Based on the hsp60 gene sequences, two previously unidentified shrimp isolates were found to be more closely related to Vibrio alginolyticus (93-94% sequence identity) than to Vibrio parahaemolyticus (89% sequence identity), whereas 16S rRNA gene analysis was unable to differentiate among these closely related species (95-97% sequence identity) . Our results indicate that the hsp60 gene may be a useful alternative target for phylogenetic analysis and species identification of marine Vibrios to complement more conventional identification systems.

Pediatr Infect Dis J, 2002 Dec, 21(12), 1136 - 41
Multicenter, randomized, double blind clinical trial of short course versus standard course oral ciprofloxacin for Shigella dysenteriae type 1 dysentery in children; Zimbabwe et al.; BACKGROUND: Shigella dysenteriae type 1 (Sd1) dysentery is associated with serious morbidity and mortality . Treatment is either costly or complicated by the emergence of bacterial resistance . This study compared the efficacy and safety of short course (3 days) and standard course (5 days) oral ciprofloxacin in children with Sd1 dysentery . METHODS: A multicenter, randomized, double blind, controlled clinical trial . Children between 1 and 12 years of age with Sd1 dysentery were randomized to receive oral ciprofloxacin suspension 15 mg/kg every 12 h for 3 days followed by placebo for 2 days or ciprofloxacin suspension for 5 days . Treatment success was defined as either resolution of illness or marked improvement on Day 6 of study . Bacteriologic cure was defined as failure to grow Sd1 on a stool sample collected on Day 6 . Clinical assessments and joint examinations were performed at baseline, at discharge and 2 weeks later . RESULTS: Of 253 patients enrolled 128 were assigned to short course ciprofloxacin and 125 to standard course ciprofloxacin . The success rates were 65 and 69% for short and standard course ciprofloxacin, respectively . All patients had bacteriologic cure, and all Sd1 isolates were susceptible to ciprofloxacin . No bacteriologic relapses occurred during the study period . Eight patients reported arthralgia . All patients had normal joint function including at follow-up . CONCLUSION: In this study twice daily ciprofloxacin for 3 days achieved clinical cure rates similar to those for the same dosage given for 5 days in children with Sd1 dysentery.

Biochemistry, 2002 Dec 24, 41(51), 15410 - 4
New UDP-GlcNAc C4 epimerase involved in the biosynthesis of 2-acetamino-2-deoxy-L-altruronic acid in the O-antigen repeating units of Plesiomonas shigelloides O17; Kowal P et al.; Plesiomonas shigelloides is a ubiquitous waterborne pathogen responsible for diseases such as diarrhea and bacillary dysentery, commonly afflicting infants and children . This bacterium is endowed with an O-antigen gene cluster consisting of 10 consecutive reading frames . One of these, designated wbgU (orf3), has been overexpressed and biochemically characterized to show that it encodes a uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) C4 epimerase, only the second microbial enzyme characterized to have this activity . Epimerization is an equilibrium reaction resulting in a 70:30 ratio of UDP-GlcNAc to uridine diphosphate-N-acetylgalactosamine (UDP-GalNAc), irrespective of the initial substrate . The K(m) values for UDP-GalNAc and UDP-GlcNAc are 131 microM and 137 microM, respectively . WbgU is also capable of converting nonacetylated derivatives but with much lower efficiency . It contains a tightly bound nicotinamide adenine dinucleotide {NAD(H)} molecule and requires no other cofactors for activity . We propose here that this enzyme catalyzes the first of the three transformations in the biosynthetic pathway of 2-acetamino-2-deoxy-L-altruronic acid, an unusual sugar present in the O-specific side chains of lipopolysaccharide of P . shigelloides O17 and its close relative Escherichia coli Sonnei.

Symp Ser Soc Appl Microbiol, 2002, (31), 136S - 143S
Quantitative assessment of risk reduction from hand washing with antibacterial soaps; Gibson LL et al.; The Centers for Disease Control and Prevention have estimated that there are 3,713,000 cases of infectious disease associated with day care facilities each year . The objective of this study was to examine the risk reduction achieved from using different soap formulations after diaper changing using a microbial quantitative risk assessment approach . To achieve this, a probability of infection model and an exposure assessment based on micro-organism transfer were used to evaluate the efficacy of different soap formulations in reducing the probability of disease following hand contact with an enteric pathogen . Based on this model, it was determined that the probability of infection ranged from 24/100 to 91/100 for those changing diapers of babies with symptomatic shigellosis who used a control product (soap without an antibacterial ingredient), 22/100 to 91/100 for those who used an antibacterial soap (chlorohexadine 4%), and 15/100 to 90/100 for those who used a triclosan (1.5%) antibacterial soap . Those with asymptomatic shigellosis who used a non-antibacterial control soap had a risk between 49/100,000 and 53/100, those who used the 4% chlorohexadine-containing soap had a risk between 43/100,000 and 51/100, and for those who used a 1.5% triclosan soap had a risk between 21/100,000 and 43/100 . The adequate washing of hands after diapering reduces risk and can be further reduced by a factor of 20% by the use of an antibacterial soap . Quantitative risk assessment is a valuable tool in the evaluation of household sanitizing agents and low risk outcomes.

J Bacteriol, 2002 Dec, 184(24), 6751 - 9
Identification of the cis-acting site involved in activation of promoters regulated by activity of the type III secretion apparatus in Shigella flexneri; Mavris M et al.; Bacteria of Shigella spp . use a virulence plasmid-encoded type III secretion (TTS) system to invade the colonic epithelium in humans . The activity of the TTS apparatus is tightly regulated in the wild-type strain and is induced upon contact of bacteria with epithelial cells, whereas it is deregulated, i.e., constitutively active, in some mutants . Under conditions of deregulated secretion, approximately 20 proteins are secreted, including VirA, OspB to OspG, and at least three members of the IpaH family, all of which are encoded by the virulence plasmid . Conditions inducing or deregulating the activity of secretion also induce the transcription of virA and four ipaH genes . The transcription of virA and ipaH9.8 requires both MxiE, a transcriptional activator of the AraC family, and IpgC, the chaperone of IpaB and IpaC, acting as a coactivator . Using reporter plasmids containing lacZ transcriptional fusions, we showed that the ipaH7.8 . ipa4.5 . ospC1, and ospF promoters are activated under conditions of deregulated secretion and that both MxiE and IpgC are necessary and sufficient for their activation in both Shigella flexneri and Escherichia coli . Promoter mapping and deletion analysis of the ipaH9.8 . virA, and ospC1 promoters identified a 17-bp motif, the MxiE box, which overlaps the -35 region and is essential for the activation of these promoters . The presence of eight MxiE boxes on the virulence plasmid suggests that 11 genes encoding secreted proteins may be regulated by the activity of secretion . We also present evidence that at least one ipaH gene that is carried by the chromosome is controlled by MxiE and IpgC.

Infect Immun, 2002 Dec, 70(12), 7050 - 3
Lactoferrin protects rabbits from Shigella flexneri-induced inflammatory enteritis; Gomez HF et al.; Shigella species cause bacillary dysentery in humans by invasion, intracellular multiplication, spread to adjacent cells, and induction of brisk inflammatory responses in the intestinal epithelium . In vitro data suggest that lactoferrin, a glycoprotein present in human mucosal secretions, has a role in protection from bacterial enteric infections . We sought to determine the activity of lactoferrin in vivo, using the concentration present in human colostrum, to investigate its effect on the development of clinical and pathological evidence of inflammation in a rabbit model of enteritis . Lactoferrin protected rabbits infected with Shigella flexneri from developing inflammatory intestinal disease . Typical histological changes in ill animals included villous blunting with sloughing of epithelial cells, submucosal edema, infiltration of leukocytes, venous congestion, and hemorrhage . Lactoferrin at a concentration normally found in human colostrum blocks development of S . flexneri-induced inflammatory enteritis.

Rev Med Chil, 2002 Sep, 130(9), 1021 - 6
{Comparison of Shigella susceptibility to commonly used antimicrobials in the Temuco Regional Hospital, Chile 1990 - 2001}; Boehme C et al.; BACKGROUND: The permanent surveillance of antimicrobial susceptibility of Shigella sp in the Temuco Regional Hospital, allowed us to define the empirical use of antimicrobials in dysenteric syndrome . AIM: To study antimicrobial susceptibility of Shigella strains collected from 1997 to May 2001 and compare the results with those reported in 1990 . MATERIAL AND METHODS: Two hundred and seventeen Shigella strains, coming from stool cultures of pediatric patients, were studied . RESULTS: In the period 1989-1990 Shigella flexneri was the main species isolated (83%) whereas, in the period 1997-2001, Shigella sonnei (55.8%) predominated . In the second period, an increase of antimicrobial resistance, as compared with the period 1989-1990, was observed for ampicillin (74.5 and 42% respectively), for cotrimoxazol (57.5 and 45% respectively) and tetracycline (64 and 8% respectively) . Chloramphenicol resistance increased from 0 to 57.5% . In the second period no resistance to ciprofloxacin was detected . There was simultaneous resistance to four drugs in 30% of the strains, predominating multiresistance in S flexneri (52.1%) . CONCLUSIONS: In the two periods studied, a significant increase was detected in the resistance of Shigella strains to antimicrobials.

J Biol Chem, 2003 Jan 31, 278(5), 2792 - 8 Epub 2002 Nov 08.
Structure-function analysis of invasion plasmid antigen C (IpaC) from Shigella flexneri; Kueltzo LA et al.; Shigella flexneri causes a self-limiting gastroenteritis in humans, characterized by severe localized inflammation and ulceration of the colonic mucosa . Shigellosis most often targets young children in underdeveloped countries . Invasion plasmid antigen C (IpaC) has been identified as the primary effector protein for Shigella invasion of epithelial cells . Although an initial model of IpaC function has been developed, no detailed structural information is available that could assist in a better understanding of the molecular basis for its interactions with the host cytoskeleton and phospholipid membrane . We have therefore initiated structural studies of IpaC, IpaC I', (residues 101-363 deleted), and IpaC Delta H (residues 63-170 deleted) . The secondary and tertiary structure of the protein was examined as a function of temperature, employing circular dichroism and high resolution derivative absorbance techniques . ANS (8-anilino-1-napthalene sulfonic acid) was used to probe the exposure of the hydrophobic surfaces under different conditions . The interaction of IpaC and these mutants with a liposome model (liposomes with entrapped fluorescein) was also examined . Domain III (residues 261-363) was studied using linker-scanning mutagenesis . It was shown that domain III contains periodic, sequence-dependent activity, suggesting helical structure in this section of the protein . In addition to these structural studies, investigation into the actin nucleation properties of IpaC was conducted, and actin nucleation by IpaC and some of the mutants was exhibited . Structure-function relationships of IpaC are discussed.

Biochemistry, 2002 Nov 19, 41(46), 13575 - 86
Molecular recognition of oligosaccharide epitopes by a monoclonal Fab specific for Shigella flexneri Y lipopolysaccharide: X-ray structures and thermodynamics; Vyas NK et al.; The antigenic recognition of Shigella flexneri O-polysaccharide, which consists of a repeating unit ABCD {-->2)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->3)-beta-D-GlcpNAc-(1-->}, by the monoclonal antibody SYA/J6 (IgG3, kappa) has been investigated by crystallographic analysis of the Fab domain and its two complexes with two antigen segments (a pentasaccharide Rha A-Rha B-Rha C-GlcNAc D-Rha A' and a modified trisaccharide Rha B-Rha C-GlcNAc D in which Rha C* is missing a C2-OH group) . These complex structures, the first for a Fab specific for a periodic linear heteropolysaccharide, reveal a binding site groove (between the V(H) and V(L) domains) that makes polar and nonpolar contacts with all the sugar residues of the pentasaccharide . Both main-chain and side-chain atoms of the Fab are used in ligand binding . The charged side chain of Glu H50 of CDR H2 forms crucial hydrogen bonds to GlcNAc of the oligosaccharides . The modified trisaccharide is more buried and fits more snugly than the pentasaccharide . It also makes as many contacts (approximately 75) with the Fab as the pentasaccharide, including the same number of hydrogen bonds (eight, with four being identical) . It is further engaged in more hydrophobic interactions than the pentasaccharide . These three features favorable to trisaccharide binding are consistent with the observation of a tighter complex with the trisaccharide than the pentasaccharide . Thermodynamic data demonstrate that the native tri- to pentasaccharides have free energies of binding in the range of 6.8-7.4 kcal mol(-1), and all but one of the hydrogen bonds to individual hydroxyl groups provide no more than approximately 0.7 kcal mol(-1) . They further indicate that hydrophobic interactions make significant contributions to binding and, as the native epitope becomes larger across the tri-, tetra-, pentasaccharide series, entropy contributions to the free energy become dominant.

Di Yi Jun Yi Da Xue Xue Bao, 2001, 21(12), 935 - 937
gyrA gene mutations in quinolone-resistant Shigellae flexneri; Xiang Q et al.; OBJECTIVE: To study the resistance mechanism of quinolone against Shigellae flexneri . METHODS: The N-terminal coding region of gyrA gene of 38 quinolone-resistant Shigellae flexneri were amplified by PCR and mutations detected by single- strand conformation polymorphism (SSCP), followed by sequence analysis . RESULTS: Eight isolates were found to be positive for gyrA mutations, and DNA sequence analysis of gyrA gene revealed 2 mutations that resulted in changes of the amino acids (Ser-83--Leu, Asp-87--Gly) . CONCLUSION: gryA gene mutations is closely related to high resistance of Shigellae flexneri to quinolone.

Indian J Med Res, 2002 Jan, 115, 11 - 3
Shigella isolation in Vellore, south India (1997-2001); Jesudason MV; Shigellosis has been a major cause of dysentery for many years at Vellore, south India . In the last two years the number of Shigella being isolated from samples of faeces from patients with diarrhoea has decreased (5% isolation rate in 1997 to 3.9% in 2001), although the microbiological methods and media used have not changed . Also, the nalidixic acid (NA) resistance has increased for S . sonnei (now 94%) . This is noteworthy, since NA has been recommended for the empirical treatment of patients suspected to have shigellosis and this concept needs to be reconsidered based on available data.

Carbohydr Res, 2002 Oct 8, 337(18), 1633 - 40
Conformation of the branched O-specific polysaccharide of Shigella dysenteriae type 2: molecular mechanics calculations show a compact helical structure exposing an epitope which potentially mimics galabiose; Rosen J et al.; Conformational analyses of the branched repeating unit of the O-antigenic polysaccharide of Shigella dysenteriae type 2 have been performed with molecular mechanics MM3 . A filtered systematic search on the trisaccharide alpha-D-GalNAc-(1-->3)-{alpha-D-GlcNAc-(1-->4)}-alpha-D-GalNAc forming the branch, shows essentially a single favored conformation . Also, the downstream alpha-D-GalNAc-(1-->4)-alpha-D-Glc linkage is sterically constrained . The alpha-D-Glc-(1-->4)-beta-D-Gal moiety, however, forms a more flexible link region between the branch points, and shows a 90 degrees bend similar to what is known for the galabiose moiety occurring in globo-glycolipids . The calculations indicate that consecutive repeating units in their minimum energy conformation arrange in a helical structure with three repeating units per turn . This helix is very compact and appears to be stabilized by hydrophobic interactions involving the N-acetyl groups at the branch points . Random conformational search suggests the existence of another helical structure with four repeating units per turn . It appears possible that the alpha-D-Glc-(1-->4)-beta-D-Gal moiety, which is exposed on the surface of the helical structures, can evade recognition by the immune system of the host by the mimicry of globo structures.

Obstet Gynecol, 2002 Nov, 100(5 Pt 2), 1063 - 5
Shigellosis complicating preterm premature rupture of membranes resulting in congenital infection and preterm delivery; Rebarber A et al.; BACKGROUND: The association of chorioamnionitis with preterm birth is well established . Intra-amniotic infection complicates 13-60% of preterm premature rupture of membranes (PROM) with enteric gram-negative pathogens accounting for 20-40% of recoverable organisms . However, the source of enteric pathogens leading to premature birth has been poorly characterized . CASE: A 36-year-old multiparous woman presented at 2567 weeks with preterm PROM . She reported a 5-day history of bloody, mucous diarrhea . A fourth cesarean delivery was performed secondary to the onset of labor . Fetal blood, placental membrane, and vaginal pool cultures revealed the presence of Shigella sonnei . With appropriate antibiotic therapy, the patient was discharged home on postoperative day 5 . Neonatal stool cultures revealed evidence of in utero fetal transmission . CONCLUSION: It is prudent to treat pregnant patients with clinical symptoms suggestive of shigellosis because this pathogen can result in preterm PROM and preterm delivery . Neonatal testing is indicated if maternal disease is suspected before delivery.

FEMS Microbiol Lett, 2002 Oct 29, 216(1), 39 - 42
Identification of shiga toxin-producing bacteria by a new immuno-capture toxin gene PCR; Luo W et al.; Infections with bacteria producing shiga toxin are responsible for widespread disease and for the death of a large number of people . In the present study, we have developed a rapid method of high specificity for the detection of Shigella dysenteriae by combining immuno-capture of the bacteria and polymerase chain reaction (PCR) amplification of their toxin gene . We compared the sensitivity of our new method, referred to as immuno-capture toxin gene PCR (iTGPCR), with a conventional TGPCR (cTGPCR) method in detecting S . dysenteriae . Approximately 100 colony forming units (CFU) of bacteria in a volume of 400 microl were divided into 20 tubes with 5 CFU (20 microl) . One group of 10 tubes was analyzed by iTGPCR and the other by cTGPCR amplification . All were positive in the 10 tubes using iTGPCR but, in contrast, only half were positive in the 10 tubes with the cTGPCR method . This method was used to detect S . dysenteriae type I in sewage samples without the normal tedious preparation methods . These findings suggest that iTGPCR gives enhanced test sensitivity, and allows determination of pathogen serotype, and differentiation of toxin-producing strains from non toxin-producing strains.

Res Microbiol, 2002 Sep, 153(7), 461 - 8
Histone-like proteins and the Shigella invasivity regulon; Prosseda G et al.; The contribution of histone-like proteins to the transcriptional regulation of virulence gene networks is a common feature among pathogenic bacteria . In this article we review current knowledge about the regulative role of major histone-like proteins in the silencing/activation of the invasivity phenotype of Shigella, the etiological agent of bacillary dissentery.

Biomedica, 2002 Sep, 22(3), 272 - 9
{Acute diarrhea outbreak caused by Shigella flexneri at a school in Madrid, Cundinamarca: phenotypic and genotypic characterization of the isolates}; Hidalgo M et al.; Shigellosis is an acute diarrhoeal disease that is the main cause of morbidity and mortality in developing countries . In 1997, the Colombian Instituto Nacional de Salud Microbiology Group organized a network surveillance program with the country's Public Health Laboratories (PHLs) to monitor the principal etiological agents responsible for acute diarrhoeal disease . In May, 2001, the PHL of the state of Cundinamarca reported a food poisoning outbreak involving an elementary school community . The main goal of the Microbiology Group involvement was to establish the molecular relationships among the isolates from the outbreak by phenotypic and genotypic methods of characterization . Stool cultures were obtained from 22 of 195 affected individuals . The Microbiology Group confirmed the identification of the isolates by biochemical and serological probes . The antimicrobial susceptibilities were tested against the following battery of antibiotics: chloramphenicol, trimehoprim-sulfamethozazole, cefotaxime, gentamicin, ampicillin and ciprofloxacin . The isolates were subjected to pulsed field gel electrophoresis (PFGE) using the following CDC (U.S . Centers for Disease Control) protocols: Xbal restriction enzyme, Shigella sonnei CDC F2353 as the reference standard, and lambda phage as a molecular weight marker . In 15 of 22 (68%) stool cultures Shigella was recovered, all isolates were identified as Shigella flexneri serotype 6 biotype Newcastle with the same antimicrobial susceptibility profile . PFGE showed that 3 (20%) isolates were identical (100% genetic similarity) and the other 12 (80%) were very closely related (genetic similarity between 86-98%) . The network system permitted the INS ready access to the isolates and the implementation of the PFGE permitted a quantitative characterization of the clonal relationship among the isolates from the outbreak.

Epidemiol Infect, 2002 Oct, 129(2), 235 - 43
Shifting serotypes, plasmid profile analysis and antimicrobial resistance pattern of shigellae strains isolated from Kolkata, India during 1995-2000; Dutta S et al.; One hundred and sixty-six shigellae strains, isolated from stool samples of paediatric patients (< 5 years old) at a Childrens' Hospital in Kolkata, India during the period of 1995-2000 were examined for serotyping, drug resistance pattern and plasmid profiles . Sh . flexneri (58 %) was found to be commonest isolate of total shigellae, followed by Sh . sonnei (28 %), Sh . boydii (9%) and Sh . dysenteriae (5%) . This profile of species was in sharp contrast to the picture obtained before 1995, when Sh . dysenteriae 1 predominated over Sh . flexneri . In Sh . flexneri strains, Sh . flexneri 2a (35%) was the most prevalent serotype, following Sh . flexneri 3a (31%), Sh . flexneri 6 (14%), Sh . flexneri 2b (11%) and Sh . flexneri 4 (9%) . Resistance patterns of the strains to 12 commonly used antimicrobial agents and minimum inhibitory concentrations (MICs) of the antibiotics were also tested . All strains were found uniformly susceptible to norfloxacin, but more than 90% strains were resistant to tetracycline, co-trimoxazole and 67% strains were resistant to ampicillin . Resistance to amoxicillin, chloramphenicol and nalidixic acid was found in 55% (range 45-74%), 46% (range 40-60%) and 29% (range 15-40%) strains respectively . Overall, shigellae strains showed statistically significant increase in resistance against tetracycline, nalidixic acid and furazolidone (P < 0.05) over the years of this study . This indicates decreased efficacy of furazolidone, cotrimoxazole and nalidixic acid for the empirical treatment of shigellosis in Kolkata . Although a few strains showed intermediate susceptibility to ciprofloxacin (4%) and cefotaxime (10%) by disk diffusion test, but the MICs of those antibiotics were within the normal limits . Almost 57% of the strains were resistant to four or more drugs with high MICs of the antibiotics . Plasmid profile analysis revealed presence of large plasmid of 220 kb in majority of the strains except in Sh . sonnei and a correlation between presence of smaller plasmids and shigellae serotypes . Hence this study reports epidemiological change of shigellae species in Kolkata, India with regard to serotypes and antibiotic resistance patterns.

FEMS Microbiol Lett, 2002 Oct 8, 215(2), 237 - 42
Doc-mediated cell killing in Shigella flexneri using a C1/LacI controlled expression system; Schofield DA et al.; In this report we describe the development of a highly stringent and dually regulated promoter system for Shigella flexneri . Dual regulation was provided by utilizing a promoter susceptible to control by the bacteriophage P1 temperature-sensitive C1 repressor that in turn was under the transcriptional control of LacI . The level of induction/repression ratios observed was up to 3700-fold in S . flexneri . The general utility of this promoter system was evaluated by demonstrating that the bacteriophage P1 post-segregational killer protein Doc mediates a bactericidal effect in S . flexneri . This represents the first report of Doc (death on curing)-mediated killing in this Gram-negative species.

Mol Med, 2002 Jul, 8(7), 405 - 16
ILG1 : a new integrase-like gene that is a marker of bacterial contamination by the laboratory Escherichia coli strain TOP10F'; Tian W et al.; BACKGROUND: Identification of differentially expressed genes between normal and diseased states is an area of intense current medical research that can lead to the discovery of new therapeutic targets . However, isolation of differentially expressed genes by subtraction often suffers from unreported contamination of the resulting subtraction library with clones containing DNA sequences not from the original RNA samples . MATERIALS AND METHODS: Subtraction using cDNA representational difference analysis (RDA) was performed on human B cells from normal or common variable immunodeficiency patients . The material remaining after the subtraction was cloned and individual clones were sequenced . The sequence of one clone with similarity to integrases (ILG1, integrase-like gene-1) was used to obtain the full length cDNA sequence and as a probe for the presence of this sequence in RNA or genomic DNA samples . RESULTS: After five rounds of cDNA RDA, 23.3% of the clones from the resulting subtraction library contained Escherichia coli DNA . In addition, three clones contained the sequence of a new integrase, ILG1 . The full length cDNA sequence of ILG1 exhibits prokaryotic, but not eukaryotic, features . At the DNA level, ILG1 is not similar to any known gene . At the protein level, ILG1 has 58% similarity to integrases from the cryptic P4 bacteriophage family (S clade) . The catalytic domain of ILG1 contains the conserved features found in site-specific recombinases . The critical residues that form the catalytic active site pocket are conserved, including the highly conserved R-H-R-Y hallmark of these recombinases . Interestingly, ILG1 was not present in the original B cell populations . By probing genomic DNA, ILG1 could only be detected in the E . coli TOP10F' strain used in our laboratory for molecular cloning, but not in any of its precursor strains, including TOP10 . Furthermore, bacteria cultured from the mouth of the laboratory worker who performed cDNA RDA were also positive for ILG1 . CONCLUSIONS: In the course of our studies using cDNA RDA, we have isolated and identified ILG1, a likely active site-specific recombinase and new member of the bacteriophage P4 family of integrases . This family of integrases is implicated in the horizontal DNA transfer of pathogenic genes between bacterial species, such as those found in pathogenic strains of E . coli, Shigella, Yersinia, and Vibrio cholera . Using ILG1 as a marker of our laboratory E . coli strain TOP10F', our evidence suggests that contaminating bacterial DNA in our subtraction experiment is due to this laboratory bacterial strain, which colonized exposed surfaces of the laboratory worker . Thus, identification of differentially expressed genes between normal and diseased states could be dramatically improved by using extra precaution to prevent bacterial contamination of samples.

Cell Microbiol, 2002 Sep, 4(9), 613 - 26
Selection of Shigella flexneri candidate virulence genes specifically induced in bacteria resident in host cell cytoplasm; Bartoleschi C et al.; We describe an in vivo expression technology (IVET)-like approach, which uses antibiotic resistance for selection, to identify Shigella flexneri genes specifically activated in bacteria resident in host cell cytoplasm . This procedure required construction of a promoter-trap vector containing a synthetic operon between the promoterless chloramphenicol acetyl transferase (cat) and lacZ genes and construction of a library of plasmids carrying transcriptional fusions between S . flexneri genomic fragments and the cat-lacZ operon . Clones exhibiting low levels (<10 micro g ml-1) of chloramphenicol (Cm) resistance on laboratory media were analysed for their ability to induce a cytophatic effect--plaque--on a cell monolayer, in the presence of Cm . These clones were assumed to carry a plasmid in which the cloned fragment acted as a promoter/gene which is poorly expressed under laboratory conditions . Therefore, only strains harbouring fusion-plasmids in which the cloned promoter was specifically activated within host cytoplasm could survive within the cell monolayer in the presence of Cm and give a positive result in the plaque assay . Pai (plaque assay induced) clones, selected following this procedure, were analysed for intracellular (i) beta-galactosidase activity, (ii) proliferation in the presence of Cm, and (iii) Cm resistance . Sequence analysis of Pai plasmids revealed genes encoding proteins of three functional classes: external layer recycling, adaptation to microaerophilic environment and gene regulation . Sequences encoding unknown functions were also trapped and selected by this new IVET-based protocol.

Infect Immun, 2002 Nov, 70(11), 6355 - 64
Shigella flexneri DegP facilitates IcsA surface expression and is required for efficient intercellular spread; Purdy GE et al.; A degP mutant of Shigella flexneri was identified in a screen for insertion mutants that invaded cultured cells but did not form wild-type plaques in monolayers . The degP mutant SM1100 invaded Henle cells at wild-type levels and induced apoptosis in macrophages but formed smaller plaques than those formed by wild-type S . flexneri in confluent monolayers of Henle and Caco-2 cells . The proportion of SM1100 bacteria with IcsA localized to the bacterial pole, a process required for actin polymerization into actin "tails," was reduced compared to results with wild-type bacteria . The reduction in proper IcsA localization may account for the reduced plaque size of the degP mutant . Although DegP is a protease, the protease activity of S . flexneri DegP was not required for IcsA localization or the formation of plaques in Henle cell monolayers . DegP was also required for efficient polar IcsA localization in E . coli expressing icsA . In addition, the growth or survival of SM1100 was compromised compared to that of the wild type at elevated temperatures and in acidic conditions.

Scand J Infect Dis, 2002, 34(9), 692 - 3
Septic shock associated with Shigella flexneri dysentery; Beigelman A et al.; Septic shock is a very unusual presentation of Shigella infection . We describe a 3-y-old child who developed severe septic shock and severe encephalopathy during an episode of dysentery caused by Shigella flexneri.

Scand J Infect Dis, 2002, 34(9), 687 - 9
Plesiomonas shigelloides sepsis in a thalassemia intermedia patient; Tzanetea R et al.; Bacteremia due to Plesiomonas shigelloides was associated with rapidly fulminant septicemia, disseminated intravascular coagulation and massive adrenal hemorrhage in a splenectomized patient suffering from thalassemia intermedia who was treated with hydroxyurea . P . shigelloides was isolated in blood cultures; despite a vigorous combination of antibiotics the patient died after 24 h in the ICU . Lethal sepsis due to P . shigelloides has not previously been reported in Greece.

Curr Biol, 2002 Sep 17, 12(18), 1617 - 22
The WH1 and EVH1 domains of WASP and Ena/VASP family members bind distinct sequence motifs; Zettl M et al.; A complex of N-WASP and WASP-interacting protein (WIP) plays an important role in actin-based motility of vaccinia virus and the formation of filopodia . WIP is also required to maintain the integrity of the actin cytoskeleton in T and B lymphocytes and is essential for T cell activation . However, in contrast to many other N-WASP binding proteins, WIP does not stimulate the ability of N-WASP to activate the Arp2/3 complex . Although the WASP homology 1 (WH1) domain of N-WASP interacts directly with WIP, we still lack the exact nature of its binding site . We have now identified and characterized the N-WASP WH1 binding motif in WIP in vitro and in vivo using Shigella and vaccinia systems . The WH1 domain, which is predicted to have a similar structural fold to the Ena/VASP homology 1 (EVH1) domain, binds to a sequence motif in WIP (ESRFYFHPISD) that is very different from the EVH1 proline-rich DL/FPPPP ligand . Interaction of the WH1 domain of N-WASP with WIP is dependent on the two highly conserved phenylalanine residues in the motif . The WH1 binding motif we have identified is conserved in WIP, CR16, WICH, and yeast verprolin.

Przegl Epidemiol, 2002, 56(2), 285 - 92
{Dysentery in Poland in 2000}; Stypulkowska-Misiurewicz H et al.; The notified number of dysentery cases is still falling down since the year 1995 when bacteriological examination of feces for diagnostic purposes lost free of charge status obtained in 1928 under the legislation act of infectious disease investigation and obligatory registration . Only 121 dysentery cases were notified in the year 2000 (incidence 0.31/100,000 population), while 292 cases were notified in 1999 (incidence 0.76/100,000) . No one death case was notified . Only 2 outbreaks (one due to S . flexneri 4a and one due to S . sonnei), both involving 26 patients, were notified in 2000, less than in 1999 when four outbreaks involving 146 patients were registered . In the year 2000, S . sonnei was the dominant etiological agent in 80% of notified dysentery cases and S . flexneri only in 20% of cases was the next . S . dysenteriae 3 was found only in one patient S . boydii in no one . All Shigella strains were susceptible to nitrofurans (ex.nifuroxaside), gentamicin, nalidixic acid, cefotaxime, and imipenem . Only two strains, including the one important from India, were susceptible to co-trimoxasole, but not to doxycycline.

Microbes Infect, 2002 Sep, 4(11), 1125 - 32
Escherichia coli in disguise: molecular origins of Shigella; Lan R et al.; Shigella, which still stands as a genus with four species today, in reality belongs to the extremely diverse species Escherichia coli . There are several lineages of Shigella strains derived through independent acquisition of the pINV virulence plasmid . The chromosomally determined phenotypic properties of Shigella result from convergent evolution during niche adaptation, most due to loss of function, some from negative selection pressure.

Microbes Infect, 2002 Sep, 4(11), 1121 - 4
Epithelial inflammation response induced by Shigella flexneri depends on mucin gene expression; Nutten S et al.; The protective effects of different mucin gene profiles on gut protection were assessed by the evaluation of TNFalpha production by intestinal epithelial cells infected by Shigella flexneri . Three HT-29 cell lines were used: HT29-G(-) (enterocyte-like cells, secreting no mucins), HT29-FU (highly expressing MUC2 and MUC4) and HT29-MTX (highly expressing MUC3 and MUC5AC) . These cells were infected either by an invasive (M90T) or the control isogenic (BS176) strains of S . flexneri, and TNFalpha mRNA production was quantified by competitive PCR . In the HT29-G(-) cells, M90T induced an increased production of TNFalpha mRNA compared to BS176, giving a TNFalpha ratio of 5.6 +/- 3.3 . In contrast, similar levels of TNFalpha mRNA were detected in HT29-FU and HT29-MTX cells stimulated with either M90T or BS176, giving ratios of 1.4 +/- 1.3 and 1.0 +/- 0.1, respectively . The results suggest that mucin genes have abilities to protect epithelial cells against S . flexneri . Furthermore, the difference in the TNFalpha ratio between the HT29-FU and HT29-MTX cells suggests distinct protective effects for these two mucin-secreting epithelial cells.

EMBO J, 2002 Oct 1, 21(19), 5069 - 78
Conversion of PtdIns(4,5)P(2) into PtdIns(5)P by the S.flexneri effector IpgD reorganizes host cell morphology; Niebuhr K et al.; Phosphoinositides play a central role in the control of several cellular events including actin cytoskeleton organization . Here we show that, upon infection of epithelial cells with the Gram-negative pathogen Shigella flexneri, the virulence factor IpgD is translocated directly into eukaryotic cells and acts as a potent inositol 4-phosphatase that specifically dephosphorylates phosphatidylinositol 4,5-bisphosphate {PtdIns(4,5)P(2)} into phosphatidylinositol 5-monophosphate {PtdIns(5)P} that then accumulates . Transfection experiments indicate that the transformation of PtdIns(4,5)P(2) into PtdIns(5)P by IpgD is responsible for dramatic morphological changes of the host cell, leading to a decrease in membrane tether force associated with membrane blebbing and actin filament remodelling . These data provide the molecular basis for a new mechanism employed by a pathogenic bacterium to promote membrane ruffling at the entry site.

Indian J Pediatr, 2002 Aug, 69(8), 687 - 95
Management of diarrhoea in practice; Singh UK et al.; Diarrhoea, a major cause of morbidity and mortality can be produced by a variety of etiological factors . Management protocol includes assessment of the child, physical examination, lab-evaluation, assessment of severity of dehydration and rehydration therapy using either of the following - WHO - ORS, Home available fluids (HAF), sugar salt solution (SSS), improve WHO-ORS, Amino acid fortified ORS, rice based ORS, low osmolarity ORS . Intravenous fluids are required if patients can't accept orally . Commonly observed electrolyte disturbances are hypernatremia, hyponatremia and hypokalemia . Concussion is a common problem and can result due to electrolyte imbalance, cavernous sinus thrombosis, associated meningitis, shigella encephalopathy and hypoglycemia in undernourished children . Treatment includes i.v . diazepam and i.v . glucose and correction of electrolyte imbalance . Additional treatment interventions include antimicrobial drugs including antibiotics, antimotility drugs, absorbents, nutritional and micro and macro nutrient supplementation.

Glimpse, 1997 Jun, 19(2), 2 - 5
Scientific achievements of the Centre, 1991-1995, in research on child survival; High-protein diet facilitates growth of children after shigellosis; PIP: Health workers randomly assigned 69 2-5 year old children recovering from shigellosis at the hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), to receive either a high-protein diet (150 kcal/kg/day with protein making up 15% of total calories) or a standard control diet (150 kcal/kg/day with protein making up 7.5% of total calories) . They received this diet for 21 days . At the end of the study, children in the high-protein diet group were significantly taller and weighed considerably more than those in the standard diet group (p ,01) . Moreover, this height spurt was maintained at 3 and 6 months (p .03 and .001, respectively) . These children also gained significantly more weight (p .01) . Prealbumin and retinol-binding protein increased significantly more among the children in the high-protein diet group than among the controls (p .01), but the mean serum albumin increases were the same . Thus this biochemical parameter suggested that the body used the extra protein to make more of the essential body proteins at a faster rate to make up for the negative nitrogen balance caused by diarrhea during acute shigellosis . Significant increases in somatomedin-C occurred in the high-protein group in comparison to the control group (p .01), indicating that the high-protein diet stimulated growth and effective protein repletion . The children in the high-protein group experienced considerably more of an increase in the fat-free mass than the others (p .01), but this mass was the same for both groups . therefore, the high-protein diet increased more deposition of fat in the muscle tissue than fat tissue . In conclusion, ICDDR,B recommended that physicians use high-protein foods with adequate calories to manage children with shigellosis to help them recover their growth quickly .

Glimpse . 1992 Nov-Dec;14(6):1, 4.
Persistent diarrhoea still a serious and difficult problem; Diarrhoea management: drug treatment; PIP: The author proposes general guidelines for the use of drugs in the treatment of diarrhea . It is stressed that antidiarrheal drugs should never be used for the routine management of acute diarrhea, especially in children under 5 years of age; rather, fluid and electrolyte replacement should be the primary treatment . Antibiotics are not indicated in patients with watery diarrhea unless cholera is suspected, in which case tetracycline or another antimicrobial agent should be used . In patients with dysentery, especially children who are febrile or appear seriously ill, antimicrobials such as ampicillin or co-trimoxazole should be given . The choice of antibiotic should be based on known antimicrobial sensitivity patterns of Shigella strains in the geographic area . Antimotility drugs may give some symptomatic relief in adults, but are contraindicated in children under 5 years of age because of the risk of depressed respiration and altered consciousness . The antisecretory drugs chlorpromazine and berberine have not yet proven practical for routine use .

Glimpse, 1982 Jan, 4(1), 2 - 4
Utilization of nutrients during and after diarrhoea; Training activities at the Centre; PIP: This article describes the international training workshops conducted by the International Center for Diarrheal Disease Research, Bangladesh (ICDDR,B) . During May 4-15, 1997, an international training course was conducted on the Laboratory Diagnosis of Common Diarrheal Disease Agents . The aim was to update the knowledge and skills of health professionals . 11 participants learned procedures for isolation and identification of pathogens, preparation of culture media, and laboratory safety . It is expected that those trained will spread their knowledge to others upon return to their home countries . A 4-week introductory course was conducted on Epidemiology and Biostatistics . The aim was to train persons from national institutions and nongovernmental organizations (NGOs) how to plan, design, analyze, and undertake epidemiological studies . A 2-week course was held on Emergency Response to Cholera and Shigella Epidemics . 12 participants from international NGOs that respond to disaster situations gained skills in managing epidemics and learning how to identify and apply measures to reduce morbidity and mortality from acute diarrhea in emergency and disaster situations . Participants learned how to recognize and manage patients with cholera and shigellosis and how to prepare an action plan for treatment and control purposes . This course consisted of theoretical lectures, hands-on training, and practical training . The Center's success in intervening in the Rwandan cholera epidemic justifies continued training for next year as well . 13 participants attended a 2-week course on Clinical Management of Diarrheal Diseases .

Afr Health, 1997 Mar, 19(3), 9 - 10
Shigella dysenteriae type 1 in Zimbabwe; Nathoo KJ; PIP: Shigella dysenteriae type 1 (SD1) is an unusually virulent enteric pathogen which causes endemic or epidemic dysentery with high death rates . SD1 has been responsible for large-scale regional outbreaks of dysentery in Africa, Central America, and south Asia . Shigella dysentery epidemics have been reported in Africa since the 1800s and overall, more than 250 million people in the African region are at risk and subject to a case fatality rate of possibly 1-10% . In Zimbabwe, the 1994 national incidence of dysentery was 13.0/1000 and the national case fatality rate was 4.5% . The transmission of SD1, its clinical presentation, management, complications, the role of the laboratory, outbreak identification and adequate preparedness, and the prevention of infection are discussed .

Child Health Dialogue . 1996;(3-4):5.
Dealing with diarrhoea; Fontaine O; PIP: Children with severe dehydration, persistent diarrhea with dehydration, or bloody diarrhea with no signs of improvement must be hospitalized . In-patient care for a child with severe dehydration includes rapid intravenous (IV) fluid therapy . Children who can still drink should be given oral rehydration salts (ORS) solution while the health worker sets up the IV drip . Children with difficulty drinking should be given ORS as soon as the IV fluid therapy restores their ability to drink (within 3-4 hours for babies, or 1-2 hours for older children), since ORS amends mineral deficiencies more effectively than the IV fluids . The IV drip should be re-administered if the child still exhibits dehydration after 3 hours for older children or 6 hours for babies . If improvement is noted, health workers should encourage the mother to administer ORS and to breast feed frequently . Hospital personnel should observe the child for at least 6 hours before discharge . This allows them to be sure that mothers can maintain the child's fluid balance . Children with diarrhea for more than 14 days face malnutrition or death . Any child with persistent diarrhea who exhibits moderate or severe malnutrition and signs of dehydration and is less than 4 months old needs to be admitted to a hospital . Management of persistent diarrhea involves fluid replacement, appropriate diet, and treatment of associated infections, if needed . ORS is usually effective for persistent diarrhea, although in a few cases poor absorption of glucose may necessitate initial rehydration with IV therapy . Breast feeding is encouraged for infants . Older infants and young children should eat 6 times a day as soon as they are able to eat . Recommended diets for these children are a low lactose diet (milk, yogurt, or curds; cooked rice; oil; sugar/glucose) and a low starch and no lactose diet (eggs, chicken, or fish; cooked rice; oil; sugar/glucose) . Children with serious infections may require nasogastric feeding at first . Shigella bacteria tend to be responsible for dysentery . Children with this bloody diarrhea should be treated with an antibiotic . If their condition does not improve and they are malnourished, less than 1 year old, were initially dehydrated, or have recently had measles, they need to be hospitalized . Drugs to reduce frequency of stools should never be given in cases of bloody diarrhea . Older babies and children should be given an extra meal and supplementary vitamins and minerals each day for two weeks .

Glimpse, 1994 Sep-Oct, 16(5), 3 - 4
Cholera epidemic among Rwandan refugees: experience of ICDDR,B in Goma, Zaire; Siddique AK; PIP: In July 1994, one of the worst cholera epidemics broke out among the nearly a million Rwandan refugees in Goma, eastern Zaire . The United Nations High Commission for Refugees estimated that nearly 12,000 people died during the epidemic . The International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) sent an eight-member medical team to Goma headed by Dr AK Siddique, a senior scientist of the Center and head of the Epidemic Control Preparedness Program, Dacca, Bangladesh . During their two-week stay, the team, in collaboration with UNICEF and the Ministry of Health, Zaire, conducted epidemiological assessment, operated a temporary treatment center and provided technical advice on case management of cholera and shigellosis to other health workers . The team also set up a microbiology laboratory in Goma to identify the pathogens responsible for the epidemic and their drug sensitivity patterns . The team visited a number of temporary treatment facilities in two of the five camp sites and provided technical advice to the health-care providers . They also visited treatment facilities in Goma city, where an estimated 200,000 refugees were affected by the epidemic . Deaths from cholera even in the treatment centers were much higher than expected . The overall case-fatality rate in the treatment centers was nearly 15% . Laboratory investigations showed that the initial epidemic was indeed caused by Vibrio cholerae strains resistant to tetracycline and doxycycline . By the first week of August, the number of cholera cases was declining, but the number of dysentery cases was increasing rapidly . Predominantly Shigella dysenteriae type 1 was responsible, which was resistant to most drugs used for treating shigellosis, except mecillinam . Inappropriate rehydration therapy and inadequate experience of health workers failed to prevent deaths . The team took over the operation of temporary treatment center at Katindo in Goma city with one of the highest case-fatality rates (14.5%) and could reduce the fatality rate to less than 1% .

Dialogue Diarrhoea, 1988 Dec, (35), 4 - 5
Mechanisms of diarrhoea and why they matter; Cutting WA; PIP: Diarrhea involves a significant increase in excreted fluid volume, due either to a failure of the bowel to reabsorb or absorb fluid or to a great increase in fluid secreted into the bowel . To cause diarrhea, pathogenic organisms must be swallowed, survive the acid in the stomach, colonize the small bowel, and stick to the enterocytes . In secretory diarrhea, Vibrio cholerae bacteria and enterotoxigenic Escherichia coli enter the enterocytes, stimulate adenylatecyclase, and cause a chain of reactions that results in the secretion of sodium and chloride ions (electrolytes)--accompanied by water--into the lumen of the bowel . In invasive diarrhea, Shigella bacteria not only colonize the surface of the small bowel but they also penetrate and invade the mucous membrane . Many enterocytes are destroyed, blood vessels may rupture, and white cells are excreted as pus along with blood and tissue fluid . Rotaviruses, a common cause of acute diarrhea in small children, penetrate the bowel in patches, killing many enterocytes and thus reducing the surface for absorption . Replacement of lost water and electrolytes is the 1st priority in the treatment of diarrhea . Examination of the diarrhea stools for blood can help to identify invasive diarrhea . Children with Shigella dysentery who seems seriously ill require specific antibiotics in addition to rehydration .

J Food Prot, 2002 Sep, 65(9), 1417 - 21
Effect of organic acids and temperature on survival of Shigella flexneri in broth at pH 4; Zaika LL; The survival of bacterial pathogens in acidified foods depends not only on the hydrogen ion concentration, but also on the type of acid and the storage temperature . Shigella flexneri is a foodborne pathogen that is acid tolerant . The survival of S . flexneri 5348 in brain heart infusion broth supplemented with 0.04 M acetic, citric, lactic, malic, or tartaric acid and adjusted to pH 4 with HCI or NaOH was studied . The control medium was brain heart infusion broth adjusted to pH 4 with HCI . Stationary-phase cells were inoculated into media at initial populations of 6 to 7 log10 CFU/ml and incubated at 4, 19, 28, and 37 degrees C . A two-phase linear inactivation model was applied to plate count data to derive lag times (tL) and slopes of the curves, from which D-values and time required for a 4-log10 decrease in population (T4D) were calculated . In all cases, survival increased with decreasing temperature . For each acid, tL, the D-value, and T4D increased with decreasing temperature . All acids inhibited S . flexneri to some extent but to differing degrees as follows: lactic acid, acetic acid > citric acid, malic acid, tartaric acid > HCl . The T4D values for the control medium and for media containing acetic, citric, lactic, malic, and tartaric acids were 64, 47, 50, 34, 58, and 52 h, respectively, at 37 degrees C and 2,607, 1,498, 1,905, 1,346, 1,726, and 2,134 h, respectively, at 4 degrees C . The results of this study indicate that organic acids may aid in the inactivation of Shigella . However, these data also suggest that foods stored at or below room temperature containing low levels (< 1%) of acids could cause illness if contaminated with Shigella.

J Bacteriol, 2002 Oct, 184(19), 5348 - 57
Three modifications in the D and T arms of tRNA influence translation in Escherichia coli and expression of virulence genes in Shigella flexneri; Urbonavicius J et al.; The modified nucleosides 2'-O-methylguanosine, present at position 18 (Gm18), 5-methyluridine, present at position 54 (m(5)U54), and pseudouridine, present at position 55 (Psi55), are located in the D and T arms of tRNAs and are close in space in the three-dimensional (3D) structure of this molecule in the bacterium Escherichia coli . The formation of these modified nucleosides is catalyzed by the products of genes trmH (Gm18), trmA (m(5)U54), and truB (Psi55) . The combination of trmH, trmA, and truB mutations resulting in lack of these three modifications reduced the growth rate, especially at high temperature . Moreover, the lack of three modified nucleotides in tRNA induced defects in the translation of certain codons, sensitivity to amino acid analog 3,4-dehydro-DL-proline, and an altered oxidation of some carbon compounds . The results are consistent with the suggestion that these modified nucleosides, two of which directly interact in the 3D structure of tRNA by forming a hydrogen bond between Psi55 and Gm18, stabilize the structure of the tRNA . Moreover, lack of Psi55 in tRNA of human pathogen Shigella flexneri leads to a reduced expression of several virulence-associated genes.

Cell Motil Cytoskeleton, 2002 Oct, 53(2), 81 - 8
Actin-based phagosome motility; Zhang F et al.; Despite abundant evidence of actin's involvement at the particle internalization stage of phagocytosis, little is known about whether phagosomes undergo the same type of actin-based motility as observed with endocytic vesicles or such intracellular pathogens as Listeria and Shigella . By employing video microscopy to follow the fate of latex bead-containing phagosomes within the cytoplasm of bone marrow macrophages, we have made the novel observation of actin-based phagosome motility . Immunofluorescence microscopy confirmed that phagosomes containing IgG-opsonized, bovine serum albumin (or BSA) -coated or uncoated latex beads all formed actin-rich rocket tails that persisted only during a brief, 1-2 min period of actin-based motility . Average speeds of actin-based phagosome motility were 0.13 +/- 0.06 microm/s for IgG-coated beads, 0.14 +/- 0.04 microm/s for BSA-coated beads, and 0.11+/- 0.03 microm/s for uncoated beads . Moreover, the speeds and motile-phase duration of each type of phagosome were comparable to the behavior of pinosomes {Merrifield et al., 1999: Nat . Cell Biol . 1:72-74.} . Determination of optimal conditions for observing and analyzing actin-based phagosome motility should facilitate future investigations of phagocytosis and phagosome maturation .

N Z Med J, 2002 Jun 21, 115(1156), 281 - 3
Geographically separate outbreaks of shigellosis in Auckland, New Zealand, linked by molecular subtyping to cases returning from Samoa; Hill PC et al.; AIM: To investigate simultaneous outbreaks of Shigella sonnei gastroenteritis occurring in February 2001 at a health camp for socially deprived children and an elderly care facility . METHODS: Those with symptoms were interviewed using a standardised questionnaire . Cases were defined as having at least three loose stools over a 24 hour period and stool samples requested . A case-control study investigating routes of transmission was performed at the health camp . Environmental investigations of food safety and hygiene were conducted at each facility . RESULTS: At the camp, 15 (37%) students and 15 (28%) staff met case criteria . Contact with human faeces (OR 4.0; 95% confidence interval 1.0-16.3; p = 0.05) and, for staff, eating camp food (OR 6.9; 1.0-5.0; p = 0.06) were shown to be independent risk factors for illness . At the elderly care facility, four (19%) residents and four (25%) staff met case criteria . Molecular subtyping confirmed that the outbreaks were related to each other and to other cases in travellers returning from Samoa to Auckland and other New Zealand cities over a four month period . CONCLUSION: Molecular subtyping is of considerable use in communicable disease investigation, providing strong evidence for links between outbreaks . With expanded technological capability, New Zealand could perform routine molecular subtyping of selected organisms to improve the detection and the investigation of regional and inter-regional outbreaks of infection.

EMBO J, 2002 Sep 2, 21(17), 4449 - 57
Initial steps of Shigella infection depend on the cholesterol/sphingolipid raft-mediated CD44-IpaB interaction; Lafont F et al.; Shigellosis is an acute inflammatory bowel disease caused by the enteroinvasive bacterium SHIGELLA: Upon host cell-Shigella interaction, major host cell signalling responses are activated . Deciphering the initial molecular events is crucial to understanding the infectious process . We identified a molecular complex involving proteins of both the host, CD44 the hyaluronan receptor, and Shigella, the invasin IpaB, which partitions during infection within specialized membrane microdomains enriched in cholesterol and sphingolipids, called rafts . We also document accumulation of cholesterol and raft-associated proteins at Shigella entry foci . Moreover, we report that Shigella entry is impaired after cholesterol depletion using methyl-beta-cyclodextrin . Finally, we find that Shigella is less invasive in sphingosid-based lipid-deficient cell lines, demonstrating the involvement of sphingolipids . Our results show that rafts are implicated in Shigella binding and entry, suggesting that raft-associated molecular machineries are engaged in mediating the cell signalling response required for the invasion process.

Rev Argent Microbiol, 2002 Apr-Jun, 34(2), 104 - 6
{Isolation of Plesiomonas shigelloides from a pediatric patient}; Turco M et al.; We report the isolation of P . shigelloides in the stools of a child with acute diarrhea living in the surroundings of Buenos Aires who usually drank untreated water . P . shigelloides has been implicated as an etiological agent in many sporadic cases of diarrhea, probably associated with drinking untreated water, eating uncooked seafood or foreign travel.

Microbiology, 2002 Aug, 148(Pt 8), 2519 - 29
Enteroinvasive Escherichia coli virulence-plasmid-carried apyrase (apy) and ospB genes are organized as a bicistronic operon and are subject to differential expression; Santapaola D et al.; In Shigella flexneri and enteroinvasive Escherichia coli (EIEC) the expression of the virulence-plasmid(pINV)-carried potential pathogenesis-associated apy gene, which encodes apyrase (ATP diphosphohydrolase), is regulated by the same regulators that govern the expression of virulence genes . To understand the transcriptional organization of the apy gene, the authors sequenced an 8023 bp PstI fragment of the pINV of EIEC strain HN280, which encompasses apy as well as its adjacent genes . The PstI fragment displays 99% identity with the corresponding fragment of pWR100, the pINV of S . flexneri strain M90T, and contains four genes . One of these genes, ospB, encodes a secreted protein of unknown activity and is located immediately upstream of apy . Analyses of sequence, Northern hybridization, RT-PCR and primer extension data and transcriptional fusions indicated that ospB and apy are co-transcribed as a 2 kb bicistronic, temperature-regulated mRNA from an upstream promoter that precedes ospB . The 2 kb mRNA is post-transcriptionally processed in the intercistronic ospB-apy region, leading to the considerable accumulation of a more stable 1 kb apy-specific mRNA (half-life of 2.2+/-0.3 min, versus 27+/-4 s for the 2 kb transcript) . Upon temperature induction, peak expression of the ospB-apy operon occurs when bacteria enter into the late phases of bacterial growth, where the apy-specific transcript was found to be much more prevalent if compared to the ospB-apy transcript.

J Appl Microbiol, 2002, 93(3), 479 - 86
Acid tolerance of Shigella sonnei and Shigella flexneri; Bagamboula CF et al.; AIMS: Determination of the behaviour of Shigella sonnei and Sh . flexneri under acid conditions . METHODS AND RESULTS: The growth and survival of Shigella spp . (9 isolates) in acidified Brain Heart Infusion (BHI) (pH 5.0-3.25 with pH intervals of 0.25) was determined after 6, 24 and 30 h incubation at 37 degrees C . Subsequently, survival of shigellae was studied in apple juice and tomato juice stored at 7 degrees C and 22 degrees C for up to 14 days and in strawberries and a fresh fruit salad, kept at 4 degrees C for 4 and 48 h . CONCLUSIONS: The minimum pH for growth in acidified BHI for Sh . flexneri and Sh . sonnei was, respectively, pH 4.75 and pH 4.50 . Survival in fruit juices and fresh fruits depended upon their pH, the type of strain and the incubation temperature . Shigella spp . Survived for up to 14 days in tomato juice and apple juice stored at 7 degrees C . The shortest survival time (2-8 d) was observed in apple juice at 22 degrees C . Sh . sonnei but not Sh . flexneri was recovered after 48 h from strawberries and fruit salad kept at 4 degrees C . SIGNIFICANCE AND IMPACT OF THE STUDY: Acid foods, especially if kept at refrigeration temperatures, support survival of Shigella spp . and may cause Shigella food poisoning.

FEMS Microbiol Lett, 2002 Aug 6, 213(2), 257 - 64
Identification of a putative pathogenicity island in Shigella flexneri using subtractive hybridisation of the S . flexneri and Escherichia coli genomes; Walker JC et al.; The genetic differences between the human pathogen, Shigella flexneri, and the non-pathogenic Escherichia coli were investigated in an attempt to identify pathogenicity islands (PAIs) in the S . flexneri genome . Genomic subtraction identified a large unique region of DNA which was present in S . flexneri serotype 2a but absent from E . coli K-12 . This 42-kb DNA segment was localised to the S . flexneri chromosome and was found to contain a number of elements often associated with PAIs including: insertion sequence elements, bacteriophage genes, and a previously identified Shigella virulence gene (criR) . These findings indicate that this region may form a new PAI in the S . flexneri genome.

Appl Environ Microbiol, 2002 Aug, 68(8), 3908 - 13
Isolation of Shigella dysenteriae type 1 and S . flexneri strains from surface waters in Bangladesh: comparative molecular analysis of environmental Shigella isolates versus clinical strains; Faruque SM et al.; Bacillary dysentery caused by Shigella species is a public health problem in developing countries including Bangladesh . Although, shigellae-contaminated food and drinks are often the source of the epidemic's spread, the possible presence of the pathogen and transmission of it through environmental waters have not been adequately examined . We analyzed surface waters collected in Dhaka, Bangladesh, for the presence of shigellae by a combination of PCR assays followed by concentration and culturing of PCR-positive samples . Analysis of 128 water samples by PCR assays for Shigella-specific virulence genes including ipaBCD, ipaH, and stx1 identified 14 (10.9%) samples which were positive for one or more of these virulence genes . Concentration of the PCR-positive samples by filtration followed by culturing identified live Shigella species in 11 of the 14 PCR-positive samples . Analysis of rRNA gene restriction patterns (ribotype) showed that the environmental isolates shared ribotypes with a collection of clinical isolates, but in contrast to the clinical isolates, 10 of the 11 environmental isolates were either negative or carried deletions in the plasmid-encoded invasion-associated genes ipaB, ipaC, and ipaD . However, all environmental Shigella isolates were positive for the chromosomal multicopy invasion-associated gene ipaH and all Shigella dysenteriae type 1 isolates were positive for the stx1 gene in addition to ipaH . This study demonstrated the presence of Shigella in the aquatic environment and dispersion of different virulence genes among these isolates which appear to constitute an environmental reservoir of Shigella-specific virulence genes . Since critical virulence genes in Shigella are carried by plasmids or mobile genetic elements, the environmental gene pool may contribute to an optimum combination of genes, causing the emergence of virulent Shigella strains which is facilitated in particular by close contact of the population with surface waters in Bangladesh.

J Bacteriol, 2002 Aug, 184(16), 4409 - 19
MxiE regulates intracellular expression of factors secreted by the Shigella flexneri 2a type III secretion system; Kane CD et al.; The mxi-spa locus on the virulence plasmid of Shigella flexneri encodes components of the type III secretion system . mxiE, a gene within this locus, encodes a protein that is homologous to the AraC/XylS family of transcriptional regulators, but currently its role in pathogenesis remains undefined . We characterized the virulence phenotype of a nonpolar mxiE mutant and found that this mutant retained the ability to invade mammalian cells in tissue culture and secrete Ipas (type III effectors required for host cell invasion), although it was less efficient than wild-type Shigella at cell-to-cell spread . Despite its invasive properties in culture, the mxiE mutant was completely avirulent in an animal model . Potential targets for MxiE activation were identified by using promoter-green fluorescent protein fusions, and gene expression was examined under various growth conditions . Six MxiE-regulated genes were discovered: ospB, ospC1, ospE2, ospF, virA, and ipaH(9.8) . Notably, activation of these genes only occurred within the intracellular environment of the host and not during growth at 37 degrees C in liquid culture . Interestingly, all of the MxiE-regulated proteins previously have been shown to be secreted through the type III secretion system and are putative virulence factors . Our findings suggest that some of these Osp proteins may be involved in postinvasion events related to virulence . Since bacterial pathogens adapt to multiple environments during the course of infecting a host, we propose that Shigella evolved a mechanism to take advantage of a unique intracellular cue, which is mediated through MxiE, to express proteins when the organism reaches the eukaryotic cytosol.

Emerg Infect Dis, 2002 Aug, 8(8), 862 - 4
Shigellosis linked to sex venues, Australia; O'Sullivan B et al.; From January 1 to July 31, 2000, 148 cases of Shigella infection were reported in New South Wales, Australia, compared with an annual average of 95 cases . Of reported cases, 83% were confirmed as Shigella sonnei biotype G infections; 80% were in homosexual men . Visiting a sex venue in the 2 weeks before onset of illness was the only factor significantly associated with shigellosis.

Anal Biochem, 2002 Aug 1, 307(1), 131 - 7
Quadrupole ion-trap mass spectrometry to locate fatty acids on lipid A from Gram-negative bacteria; Kussak A et al.; The structure of lipid A released by mild acid hydrolysis from lipopolysaccharide from two strains of Shigella flexneri with different degrees of acylation was characterized using electrospray ionization (ESI) and ion-trap mass spectrometry . The lipid A was analyzed underivatized with ESI in negative-ion mode . With multiple stages of fragmentation (MS(n)), both the degree of acylation and the positions of the fatty acids on the disaccharide backbone could be determined . It was possible to determine the degree of acylation by the MS(n) technique, where in each MS stage the parent ion was an ion where one fatty acid had been eliminated . One way to determine the location of the fatty acids was by identifying cross-ring fragments of the reducing sugar from parent ions containing different numbers of fatty acids . Another was by identifying a possible charge-driven release of fatty acids situated close to a phosphate group . The fatty acids were otherwise eliminated by a charge-remote fragmentation mechanism . The combined data show the usefulness of ion-trap mass spectrometers for this type of analysis.

Kansenshogaku Zasshi, 2002 Jun, 76(6), 466 - 9
{A fatal case of shigellosis in an elderly patient}; Imamura S et al.; A 71 year-old male, with no recent history of travelling abroad and a past history of lung cancer two years prior to presentation, which had been successfully treated, developed a sudden onset of watery diarrhea more than ten times a day on February 26, 2001, which gradually became bloody . The next day he visited the Department of Integrated Medicine of the Tokyo Metropolitan Komagome Hospital by ambulance because his consciousness was deteriorating and he was hospitalized . He was hypotensive on admission, and a dopamine preparation was used throughout . The peripheral WBC was 3,800/microliter and the lymphocyte count was 76/microliter which thus suggested the presence of cellular immune suppression . HIV was not tested . He died seven hours after admission . His stool culture yielded a growth of Shigella flexneri 2a, and a blood culture on admission was sterile . No verocyte toxin-producing Esherichia coli was not detected . The causes of death in cases with shigellosis have been reported in the literature to be an electrolyte imbalance, septicemia and disseminated intravasucular coagulation (DIC) in developed countries . Our present case was considered to be a debilitated patient complicated with hemolytic uremic syndrome due to an infection with Shigella bacteria which resulted in death despite performing intensive treatments.

Tidsskr Nor Laegeforen, 2002 Jun 20, 122(16), 1568 - 72
{Health hazards for immigrants when travelling to their home countries}; Brunvatne R et al.; Vacations in the home country are important and positive events in the lives of immigrants, events that allow them to maintain contact with their culture, relatives and friends . However, vacations also carry certain health risks, though these risks can to some degree be prevented . Infectious disease is the greatest risk . Some children and adolescents also run the risk of female genital mutilation, forced marriage, and the risk og being left behind in the home country against their will . Among the notifiable diseases registered with the Norwegian Surveillance System for Communicable Diseases (MSIS), five stand out as having a higher incidence in people of foreign background than in people of Norwegian origin: malaria, hepatitis A, shigella infection, typhoid and paratyphoid fever . This higher incidence is partly the result of less use of pre-travel vaccines and malaria prophylaxis . Immigrants as a group are exposed to varied risks and should be given high priority in relation to vaccines and malaria prophylaxis for travel abroad . High priority should also be given to preventive health measures designed to reduce the risk of female genital mutilation and other violations against children and young people on visit to their country of origin.

Infect Immun, 2002 Aug, 70(8), 4379 - 88
Identification of chromosomal Shigella flexneri genes induced by the eukaryotic intracellular environment; Runyen-Janecky LJ et al.; Upon entry into the eukaryotic cytosol, the facultative intracellular bacterium Shigella flexneri is exposed to an environment that may necessitate the expression of particular genes for it to survive and grow intracellularly . To identify genes that are induced in response to the intracellular environment, we screened a library containing fragments of the S . flexneri chromosome fused to a promoterless green fluorescent protein gene (gfp) . Bacteria containing promoter fusions that had a higher level of gfp expression when S . flexneri was intracellular (in Henle cells) than when S . flexneri was extracellular (in Luria-Bertani broth) were isolated by using fluorescence-activated cell sorting . Nine different genes with increased expression in Henle cells were identified . Several genes (uhpT, bioA, and lysA) were involved in metabolic processes . The uhpT gene, which encoded a sugar phosphate transporter, was the most frequently isolated gene and was induced by glucose-6-phosphate in vitro . Two of the intracellularly induced genes (pstS and phoA) encode proteins involved in phosphate acquisition and were induced by phosphate limitation in vitro . Additionally, three iron-regulated genes (sufA, sitA, and fhuA) were identified . The sufA promoter was derepressed in iron-limiting media and was also induced by oxidative stress . To determine whether intracellularly induced genes are required for survival or growth in the intracellular environment, we constructed mutations in the S . flexneri uhpT and pstS genes by allelic exchange . The uhpT mutant could not use glucose-6-phosphate as a sole carbon source in vitro but exhibited normal plaque formation on Henle cell monolayers . The pstS mutant had no apparent growth defect in low-phosphate media in vitro but formed smaller plaques on Henle cell monolayers than the parent strain . Both mutants were as effective as the parent strain in inducing apoptosis in a macrophage cell line.

Epidemiol Infect, 2002 Jun, 128(3), 533 - 5
Prevalence of the genes for shigella enterotoxins 1 and 2 among clinical isolates of shigella in Israel; Yavzori M et al.; Two enterotoxins, shigella enterotoxin 1 (SHET1) and shigella enterotoxin 2 (SHET2) have been recently characterized and are believed to play a role in the clinical manifestation of shigellosis . One hundred and twenty-one isolates of Shigella spp . of 13 different serotypes and variants and 10 isolates of enteroinvasive Escherichia coli (EIEC) isolated in Israel, were examined by polymerase chain reaction for the presence of SHET1 and SHET2 genes . SHET1 was only prevalent among isolates of S . flexneri 2a while SHET2 was found in all the serotypes that were tested except for several isolates of S . flexneri 1b that lost their virulence plasmid during storage . In addition, we found that the S . flexneri 2a vaccine strain T-32 Istrati contains the gene encoding for SHET1 but not that encoding for SHET2, suggesting that the latter is located within a large deletion occurring in the 140 Mda plasmid of this S . flexneri 2a non-invasive vaccine strain.

J Clin Microbiol, 2002 Jul, 40(7), 2490 - 7
Phenotypic and genotypic characterization of serologically atypical strains of Shigella flexneri type 4 isolated in Dhaka, Bangladesh; Talukder KA et al.; Twenty-one atypical Shigella flexneri type 4 strains isolated from patients attending the Dhaka treatment center of the International Centre for Diarrhoeal Disease Research, Bangladesh, were extensively characterized and compared with S . flexneri serotypes 4a and 4b . The atypical strains agglutinated only with the type antigen factor 4 and did not agglutinate with any group factors, thereby excluding their characterization into serotype 4a or 4b . Of the 21 strains, 85.7% did not ferment mannitol but were able to ferment most of the sugars, whereas the remaining 14.3% strains fermented mannitol but were unable to ferment most of the sugars . Most of the strains were resistant to ampicillin, tetracycline, and trimethoprim-sulfomethoxazole . All of the strains harbored the 140-MDa plasmid, had the ipaH gene, had the sen gene (encoding Shigella enterotoxin 2), had the ability to bind Congo red, and were positive for keratoconjunctivitis in the guinea pig eye, attesting their invasive properties . All of the strains contained a middle-range plasmid (35 to 62 MDa) as well as a number of stable small plasmids, yielding mainly two plasmid profiles which were different from those of 4a and 4b strains . Conjugation and curing experiments suggested that the middle-range plasmids harbored a self-transferable multiple antibiotic resistance marker . Pulsed-field gel electrophoresis analysis of all of the tested strains yielded two types with numerous subtypes, whereas ribotyping yielded only two types which were completely different from those of types 4a and 4b . This study concluded that two different clones of atypical S . flexneri type 4 exist and strongly suggests that these are new subserotypes of S . flexneri that await further serological classification.

J Travel Med, 2002 May-Jun, 9(3), 137 - 40
Enterotoxigenic Escherichia coli as cause of diarrhea among Mexican adults and US travelers in Mexico; Bouckenooghe AR et al.; BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) is the most common pathogen identified in travelers to Mexico with diarrhea . There have been few recent studies looking at the etiology of diarrhea in travelers compared with the local resident population . METHODS: We compared enteric pathogens isolated in two populations experiencing acute diarrhea acquired in Guadalajara, Mexico and also compared clinical illness caused by the principal pathogen, ETEC . RESULTS: A single and 2 enteropathogens were detected in 107 (23%) and 8 (2%), respectively, of 457 Mexicans in 1995 and 1997, and 37 (29%) and 2 (2%), respectively, of 127 US adults in 1997 . The most common pathogen was ETEC in both groups (11% of Mexican, 19% of US adults), although more common in the US travelers group (p =.0017) . Shigella spp and Cryptosporidium spp were less common in the Mexican (<1% and <1%, respectively) than in the travelers group (6% and 3%, respectively) (p <.001 and p =.002, respectively) . Entamoeba histolytica was more often found in the Mexican group (4% Mexican, 0% US adults; p =.027) . CONCLUSION: ETEC is the most common pathogen among travelers and Mexican residents in this study . The duration of untreated diarrhea due to ETEC was significantly shorter among Mexicans (49 hours in Mexican, 94 hours in US adults; p =.0004), as was the average number of unformed stools passed over 4 days (Mexicans 8.8 versus travelers 17.9 stools; p =.0009

Nippon Rinsho, 2002 Jun, 60(6), 1089 - 94
{Effect of cytokines on the expression of Shiga toxin toxicity}; Nakane A et al.; Shiga toxins(Stxs), which are produced by enterohemorrhagic Escherichia coli and Shigella dysenteriae serotype I, induce proinflammatory cytokines including tumor necrosis factor-alpha, interleukin(IL)-1 beta, IL-6, interferon-gamma, and chemokines such as IL-8 in intestinal epithelial cells, vascular endothelial cells, and monocytes/macrophages in vitro and in kidneys and spleen in vivo . Cytokines induced by Stxs and lipopolysaccharide enhance the toxicity of Stxs via up-regulation of the expression of Gb3, a Stx receptor, and infiltration of neutrophils . Stxs bind to neutrophils and transmigrate across intestinal mucosa and are transported to the target organs through bloodstreams . Stxs induce cytokines in vascular endothelial cells and peripheral blood monocytes and may injure organ tissues, finally resulting in hemolytic uremic syndrome and encephalopathia.

Prep Biochem Biotechnol, 2002 May, 32(2), 143 - 55
Purification of lactoperoxidase from creek-water buffalo milk and investigation of kinetic and antibacterial properties; Ozdemir H et al.; Water buffalo lactoperoxidase (WBLP) was purified with Amberlite CG 50 H+ resin, CM Sephadex C-50 ion-exchange chromatography, and Sephadex G-100 gel filtration chromatography from skim milk . All purification steps of the WBLP were shown with SDS-PAGE and Rz (A412/A280) controlled the purification degree of the enzyme . Rz value for the purified WBLP was 0.8 . To determine purification steps and kinetic properties, the activity of enzyme was measured by using 2,2-azino-bis-(3-ethylbenzthiazoline-6 sulfonic acid) diammonium salt (ABTS) as a choromogenic substrate at pH=6 . Km, Vmax, optimum pH, and optimum temperature for the WBLP were found by means of graphics for ABTS as substrates . Optimum pH and optimum temperature of the WBLP were 6 and 60 degrees C, respectively . Km value at optimum pH and optimum temperature for the WBLP was 0.82 mM . Vmax value at optimum pH and optimum temperature was 13.7 micromol/mL x min . Km value at optimum pH and 25 degrees C for the WBLP was 0.77 mM . Vmax value at optimum pH and 25 degrees C was 4.83 micromol/mL x min . The purified WBLP was found to have high antibacterial activity in a thiocynate-H2O2 medium for some pathogenic bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginose, Shigella sonnei, Staphylococcus saphrophyticus, Staphylococcus epidermidis, and Shigella dysenteriae and compared with well known antibacterial substances such as tetracycline, penicillin, and netilmicine.

Vet Microbiol, 2002 Jul 22, 87(4), 341 - 52
Shiga toxin genes in avian Escherichia coli; Parreira VR et al.; The purpose of this study was to determine the presence of stx genes in avian pathogenic Escherichia coli (APEC) . We examined 97 APEC isolates: 34 from lesions of avian cellulitis, 31 from avian septicemia, 13 from swollen head syndrome (SHS) in chickens, and 19 from diseased turkeys . We also examined five isolates from the feces of healthy chickens . All 102 E . coli isolates were tested for the presence of stx genes by PCR amplification and by colony blots using probes specific for stx1 and stx2 . Fifty-three percent (52) of the 97 APEC carried stx gene sequences: one isolate carried stx2 sequences, two carried both stx1 and stx2 sequences, and the remaining 49 isolates carried only stx1 sequences . Twenty-six isolates were positive by both hybridization and PCR amplification, 10 were positive by PCR only, and 16 were positive by hybridization only . All the stx-positive isolates were negative by PCR for the eae and E-hlyA genes . The five isolates from healthy chickens were all negative for stx . All 13 SHS isolates were positive for the stx1 gene and had low titres for cytotoxicity in the Vero cell assay (VCA) . Other stx-positive isolates were negative in the VCA . The stx1 gene from one SHS E . coli isolate was cloned and sequenced and shown to be identical to that of the stx gene of Shigella dysenteriae . The observations indicate that stx1 gene sequences are widespread among APEC but that cytotoxicity on Vero cells is uncommon.

Cell Microbiol, 2002 Jun, 4(6), 367 - 81
Shigella flexneri regulates tight junction-associated proteins in human intestinal epithelial cells; Sakaguchi T et al.; Shigella spp . are a group of Gram-negative enteric bacilli that cause acute dysentery in humans . We demonstrate that Shigella flexneri has evolved the ability to regulate functional components of tight junctions after interaction at the apical and basolateral pole of model intestinal epithelia . In the regulation of tight junctional protein assemblies, S . flexneri can engage serotype-specific mechanisms, which targets not only expression, but also cellular distribution and membrane association of components of tight junctions . Distinct mechanisms resulting in the regulation of tight junction-associated proteins are initiated after either apical or basolateral interactions . S . flexneri serotype 2a has the ability to remove claudin-1 from Triton X-insoluble protein fractions upon apical exposure to T-84 cell monolayers . S . flexneri serotype 2a and 5, but not the non-invasive Escherichia coli strain F-18, share the ability to regulate expression of ZO-1, ZO-2, E-cadherin and to dephosphorylate occludin . The disruption of tight junctions is dependent on direct interaction of living Shigella with intestinal epithelial cells and is supported by heat-stable secreted bacterial products . Intestinal epithelial cells have the ability to compensate in part for S . flexneri induced regulation of tight junction-associated proteins.

Infect Immun, 2002 Jul, 70(7), 3833 - 42
Human monocytes kill Shigella flexneri but then die by apoptosis associated with suppression of proinflammatory cytokine production; Hathaway LJ et al.; Shigella flexneri infection of human macrophages is followed by rapid bacterial escape into the cytosol and secretion of IpaB, which activates caspase-1 to mediate cell death and release of mature interleukin (IL)-1 beta . Here we report a different outcome following infection of human peripheral blood monocytes . S . flexneri infects monocytes inefficiently in the absence of complement and, following complement-dependent uptake, cannot escape the endosomal compartment . Consequently, bacteria are killed within the first 60 min in the absence of monocyte cell death, as demonstrated by immunofluorescence and electron microscopy and enumeration of colonies in a gentamicin protection assay . Despite early bacterial death, wild-type S . flexneri influenced the subsequent monocyte proinflammatory cytokine response and cell fate . Infection with wild-type S . flexneri resulted in IpaB-dependent suppression of IL-1 beta, tumor necrosis factor alpha, and IL-6 compared with that of plasmid-cured avirulent S . flexneri-infected cells . Furthermore, over the following 6 to 8 h, virulent S . flexneri-infected monocytes died by apoptosis whereas avirulent infected monocytes died by necrosis . Together, these results imply that monocytes migrating into the inflammatory site during the early stages of shigellosis kill S . flexneri but that during bacterial uptake, they receive virulence signals from S . flexneri which induce delayed apoptosis associated with suppression of the proinflammatory cytokine response to bacterial phagocytosis . This delayed apoptosis may have important effects on the ordered initiation of the innate immune response, leading to the excessive inflammatory response characteristic of shigellosis.

EMBO J, 2002 Jun 17, 21(12), 2923 - 35
Shigella deliver an effector protein to trigger host microtubule destabilization, which promotes Rac1 activity and efficient bacterial internalization; Yoshida S et al.; Shigella deliver a subset of effectors into the host cell via the type III secretion system, that stimulate host cell signal pathways to modulate the actin dynamics required for invasion of epithelial cells . Here we show that one of the Shigella effectors, called VirA, can interact with tubulin to promote microtubule (MT) destabilization, and elicit protrusions of membrane ruffling . Under in vitro conditions, VirA inhibited polymerization of tubulin and stimulated MT destabilization . Upon microinjection of VirA into HeLa cells, a localized membrane ruffling was induced rapidly . Overexpression of VirA in host cells caused MT destruction and protruding membrane ruffles which were absent when VirA was co-expressed with a dominant-negative Rac1 mutant . Indeed, Shigella but not the virA mutant stimulated Rac1, including the formation of membrane ruffles in infected cells . Importantly, the MT structure beneath the protruding ruffling was destroyed . Furthermore, drug-induced MT growth in HeLa cells greatly enhanced the Shigella entry . These results indicate that VirA is a novel type of bacterial effector capable of inducing membrane ruffling through the stimulation of MT destabilization.

Int J Syst Evol Microbiol . 2002 May;52(Pt 3):1041.
Bacillus dysentericus (sic) 1897 was the first taxonomic rather than Bacillus dysenteriae 1898; Yabuuchi E; The basonym of Shigella dysenteriae (Shiga 1898) Castellani and Chalmers 1919 was first and officially proposed in 1897 as Bacillus dysentericus (sic) in Saikingaku Zasshi, published in Japan . In accordance with Section 6 (Citation of Authors and Names) of the Bacteriological Code (1990 Revision), the year of the first proposal of Shigella dysenteriae has to be corrected from Bacillus dysenteriae 1898 to Bacillus dysentericus (sic) 1897.

Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao (Shanghai), 2001, 33(3), 277 - 280
Expression of Colonization Factor Antigen I of Enterotoxigenic Escherichia coli in Shigella flexneri 2a T32; Zhang B et al.; A host-plasmid lethal balancing system was constructed based on asd gene in an avirulent strain of S.flexneri to express colonization factor antigen I(CFA-I) of enterotoxigenic Escherichia coli.The results of Western blotting suggested that avirulant strain of S.flexneri Fwl01 expressed CFA-I steadily . Examination of negatively-stained preparation of cultures by electron microscopy showed that S.flexneri Fwl01 carrying the plasmid pZHY21 had thick pili on its surface . Antibodies against CFA-I were decteted in sera of mice immunized with recombinant bacteria either orogastrically (o.g.) or intranasally(i.n.); simultaneously sIgA against CFA-I was also decteted in the intestine . This work is helpful for constructing multivalent reombinant vaccine for prevention of bacterial diarrhea.

Rev Med Chil, 2002 Mar, 130(3), 275 - 80
{Molecular characterization of resistance mechanisms to chloramphenicol in Shigella flexneri strains isolated from Chilean children with acute diarrhea}; Farfan M et al.; BACKGROUND: Chloramphenicol is one of the therapeutic options for shigellosis, but resistance to this antimicrobial is increasing . AIM: To characterize molecular mechanisms conferring resistance to chloramphenicol (Cm) in Shigella flexneri strains isolated from Chilean children with acute diarrhea . MATERIAL AND METHODS: Thirty one Shigella filexneri strains, including 22 with the Cm phenotype were analyzed . Strains were tested for antimicrobial susceptibility by plate dilution and for the presence of an internal fragment of the cat gene encoding for chloramphenicol o-acetyl-transferase, by polymerase chain reaction and Southern blot analysis . RESULTS: All Cm strains had a minimal inhibitory concentration over 64 micrograms/ml and amplified the internal fragment of the cat gene . Southern blot analyses indicated that this gene was located in the bacterial chromosome . CONCLUSIONS: Resistance to chloramphenicol in this group of Shigella flexneri strains was mediated by a chromosomally located cat gene.

Zh Mikrobiol Epidemiol Immunobiol, 2002 Mar-Apr, (2), 77 - 9
{Clinical and morphological aspects of shigellosis flexneri in patients with an aggravated premorbid state}; Iushchuk ND et al.; The analysis of 10 fatal outcomes in patients with acute shigellosis during the period of 1999-2000 made it possible to find out that most of deceased shigellosis patients belonged to the group inclined to alcohol abuse and having initial alimentary disturbances . In 6 cases of acute shigellosis with fatal outcome the causative agent was S . flexneri 2a, in 2 cases--S . flexneri 3a, in 1--S . flexneri 4b . The main cause of fatal outcomes was accompanying double pneumonia . Lesions of the intestinal tract in deceased shigellosis patients were of destructive character, resulting, in a number of cases, in serous and perforative peritonitis.

Zh Mikrobiol Epidemiol Immunobiol, 2002 Mar-Apr, (2), 6 - 9
{Diversity within a population of Shigella sonnei according to markers of medicinal preparations}; Markova IuA et al.; As revealed in this study, S . sonnei population is represented by two clusters with respect to the sensitivity to different antibiotics . A higher degree of diversity was observed with respect to the action of streptomycin, kefzol, ampicillin, chloramphenicol and kanamycin in comparison with the action of gentamicin, nevigramon, rafampicin, tetracycline and polymyxin . The level of diversity of S . sonnei with respect to the sensitivity to antibiotics under study underwent essential changes during the calendar year . The distributions obtained study quite closely corresponded to changes in Sonne dysentery morbidity observed within the year period: the first cluster corresponded to the period of morbidity between the seasons and the second one, to the seasonal period of morbidity . The minimal coefficient of diversity fell on May while the maximum--on September . The minimal level of S . sonnei diversity, as a rule, corresponds to the minimum biosystems stability.

Southeast Asian J Trop Med Public Health, 2001 Dec, 32(4), 856 - 62
Antimicrobial resistance of Shigella spp isolated from diarrheal patients between 1989 and 1998 in Vietnam; Anh NT et al.; Shigellosis is an important cause of infectious diarrhea in Vietnam, caused mainly by Shigella flexneri . This study provides for the first time in the international literature, data on the development of antimicrobial resistance in Shigella between 1988 to 1998, including data reported to the National Program for Surveillance of Antimicrobial Resistance (NPSAR) . Our studies show that about 80% of the Shigella strains tested were resistant to ampicillin, chloramphenicol, oxytetracycline, trimethoprim and sulfonamides . This combination of drugs was also the most common antibiogram among multiple-resistant S . flexneri (57%) . Resistance to tetracyclines, sulfonamides and, in particular trimethoprim (p<0.001), increased during the study period . Our findings indicate that tetracyclines and co-trimoxazole (a combination of a sulfonamide and trimethoprim), which are recommended and commonly used drugs for the treatment of shigellosis in Vietnam, may have limited therapeutic effect . In contrast to neighboring countries, low percentages of resistance were found to nalidixic acid and norfloxacin (3-5%) and no resistance was found to ciprofloxacin, indicating that nalidixic acid with its low cost and safety in children could be recommended for the treatment of shigellosis . The NPSAR provides a useful picture of the levels and development of antimicrobial resistance in Vietnam and should receive continued support for further improvement by increasing the number of provinces covered, the numbers of isolates tested from rural areas, and the communication of results to medical practitioners and others prescribing and/or selling antimicrobials.

J Am Coll Nutr, 1999 Aug, 18(4), 303 - 8
Acute diarrhea and malnutrition: lethality risk in hospitalized infants; Fagundes-Neto U et al.; OBJECTIVES: Acute diarrhea is a very frequent disease in developing countries and is the first cause of death in infants under two years of age . This study was designed to evaluate the clinical and epidemiological factors associated to the death of 17 out of 511 infants hospitalized due to severe acute diarrhea between January 1989 and December 1995 . PATIENTS AND METHODS: The patients were divided into two groups according to their clinical evolution: Group I--Death and Group II--Survival . The following parameters were evaluated: birth weight, gender, age, duration of diarrhea (days) prior to admission, nutritional status, hydration, presence of an enteropathogenic agent in the stools, food intolerance and duration of hospitalization . RESULTS: The analyzed factors have shown a significant association with death for the following variables: age, relative factor of death (RFD)=4.0 for infants less than six months of age, identification of an enteropathogenic Escherichia coli (EPEC) strain in the stools (RFD=3.3), severe malnutrition at admission to the hospital (RFD=4.5), occurrence of food intolerance during hospitalization (RFD=2.7) . Some enteropathogenic agent was identified in the stools of 253 infants (54.9%), among the 461 (90.2%) studied . Group I revealed the presence of an enteropathogenic agent in 75% of the cases . The most frequent agents identified in Group I were: EPEC (56.3%) and Shigella (12.5%), while in Group II EPEC was identified in 26.5% of the patients . CONCLUSIONS: The association of some factors, such as age less than six months, severe malnutrition, food intolerance and the identification of EPEC strains in the stool culture, indicate a high risk of death in infants hospitalized due to severe acute diarrhea.

J Food Prot, 2002 May, 65(5), 774 - 9
The effect of NaCl on survival of Shigella flexneri in broth as affected by temperature and pH; Zaika LL; Shigella, a major foodborne pathogen, survives well in salt-containing environments . However, systematic data are scarce . We studied the behavior of Shigella flexneri 5348 in brain heart infusion broth (pH 4 to 6) containing 0.5 to 8% NaCl . Stationary-phase cells were inoculated into sterile media at initial concentrations of 6 to 7 log10 CFU/ml and incubated at 12 to 37 degrees C . Bacterial population sizes were determined periodically by plate counts . Survivor curves were derived from plate count data by using a two-phase linear model to determine lag times and slopes of the curves, from which decimal reduction times (D-values) and times to a 4-log10 inactivation (T4D) were calculated . In media of pH 6, the bacteria grew in the presence of < or = 6% NaCl at 19 and 37 degrees C and in the presence of < or = 7% NaCl at 28 degrees C . In media of pH 5, growth was observed in the presence of < or = 2, < or = 4, < or = 4, and 0.5% NaCl at 37, 28, 19, and 12 degrees C, respectively . Growth did not occur and bacterial populations gradually declined in media of pH 4 . While NaCl had a major effect on growth, bacterial survival was affected to a lesser extent . Lag times decreased with increasing NaCl levels; however, the effect on D-values and T4D values was less pronounced . The average T4D values for media of pH 4 containing 0.5 to 6% NaCl were 4, 13, 23, and 61 days at 37, 28, 19, and 12 degrees C, respectively . These results show that S . flexneri is salt tolerant and suggest that salty foods may serve as vehicles for infection with this bacterium.

Kansenshogaku Zasshi, 2002 Apr, 76(4), 275 - 9
{Shigella boydii strains possessing a new serovar (SM00-27) isolated from diarrhea of overseas travelers in Japan}; Matsushita S et al.; Five Shigella strains isolated from stool cultures of five sporadic imported diarrheal cases in Japan during 1999-2001, did not react to any antisera of the established Shigella serovars . These strains had the typical biochemical characteristics of Shigella boydii, and were biochemically identical . All strains were positive in a PCR assay and a cultured-cell invasion test for invasiveness; these indicate that they can cause shigellosis in humans . The results of antigenic analysis revealed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable . Strain SM00-27 is designated as the test strain for this new S . boydii serovar.

Curr Microbiol, 2002 Jul, 45(1), 63 - 9
Distinct recent lineages of the strA- strB streptomycin-resistance genes in clinical and environmental bacteria; Sundin GW; We report the linkage of the strA-strB streptomycin-resistance genes with Class 1 integron sequences on pSTR1, a 75-kb multiple antibiotic-resistance plasmid from Shigella flexneri . strA-strB had previously been detected only within Tn 5393, a Tn 3-family transposon, and on small nonconjugative broad-host-range plasmids such as RSF1010 . The geographic range of Tn 5393 was also extended to Pseudomonas spp . isolated from apple trees in New Zealand and soil in the USA . Comparative sequence analyses indicated that strA-strB from Tn 5393 and nonconjugative plasmids constitute distinct recent lineages with strA-strB from pSTR1 intermediate between the other two . The carriage of strA-strB within an integron, a transposon, and on broad-host-range plasmids has facilitated the world-wide dissemination of this determinant among at least 21 bacterial genera.

Pac Health Dialog, 2001 Mar, 8(1), 99 - 102
Death from multi-resistant shigellosis in Fiji Islands; Watson C; Death from Shigellosis is rare in developed countries, however it causes over a million deaths in developing countries worldwide annually . Death from shigellosis is rare in Fiji . However, the global problem of emerging multidrug resistance raises some issues about the management of Shigellosis in this country . Within Fiji, Shigella is a notifiable disease . The Fiji Ministry of Health recorded 68 cases of Shigella in 1996, 173 cases in 1997 and 334 cases in 1998 (no data available for 1999) . There was only one recorded death during this time--in 1998 . Resistance to chloramphenicol occurred in 82% of cases . Shigella flexneri in Fiji remains sensitive to cephalothin and cefaclor . The current antibiotic guidelines in Fiji, recommend that antibiotics be used only for cases of moderate and severe dysentery . Shigellosis was suspected soon after presentation however the patient was unable to take oral antibiotics and was treated with intravenous antibiotics (chloramphenicol and ampicillin), which were ineffective due to resistance of the organism . The current antibiotic guidelines for severe dysentery recommend chloramphenicol or nalidixic acid--the later not available in Fiji . However the only intravenous drugs that retain their sensitivity to Shigella-ceftriaxone and cephalothin, are expensive ($F 45.00 per vial of ceftriaxone) and these are only available in large regional hospitals.

Infect Immun, 2002 Jun, 70(6), 3199 - 207
Apoptosis in acute shigellosis is associated with increased production of Fas/Fas ligand, perforin, caspase-1, and caspase-3 but reduced production of Bcl-2 and interleukin-2; Raqib R et al.; Shigella dysenteriae type 1-induced apoptotic cell death in rectal tissues from patients infected with Shigella dysenteriae type 1 was studied by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) technique and annexin V staining . Expression of proteins and cytokines participating in the apoptotic process (caspase-1, caspase-3, Fas {CD95}, Fas ligand {Fas-L}, perforin, granzyme A, Bax, WAF-1, Bcl-2, interleukin-2 {IL-2}, IL-18, and granulocyte-macrophage colony-stimulating factor) in tissue in the acute and convalescent stages of dysentery was quantified at the single-cell level by in situ immunostaining . Apoptotic cell death in the lamina propria was markedly up-regulated at the acute stage (P < 0.05), where an increased number of necrotic cells were also seen . Phenotypic analysis of apoptotic cells revealed that 43% of T cells (CD3), 10% of granulocytes (CD15), and 5% of macrophages (CD56) underwent apoptosis . Increased activity of caspase-1 persisted in the rectum up to 1 month after onset . More-extensive expression of Fas, Fas-L, perforin, caspase-3, and IL-18, but not IL-2, at the acute stage than at the convalescent stage was observed . Increased expression of caspase-3 and IL-18 in tissues with severe inflammation compared to expression in those with mild inflammation was evident, implying a possible role in the perpetuation of inflammation . Significantly reduced cell death during convalescence was associated with a significant up-regulation of Bcl-2, Bax, and WAF-1 expression in the rectum compared to that in the acute phase of infection . Thus, induction of apoptosis at the local site in the early phase of S . dysenteriae type 1 infection was associated with a significant up-regulation of Fas/Fas-L and perforin and granzyme A expression and a down-regulation of Bcl-2 and IL-2, which promote cell survival.

Infect Immun, 2002 Jun, 70(6), 2950 - 8
Construction, characterization, and animal testing of WRSd1, a Shigella dysenteriae 1 vaccine; Venkatesan MM et al.; WRSd1 is a Shigella dysenteriae 1 vaccine containing deletions of the virG(icsA) gene required for intercellular spreading and a 20-kb chromosomal region encompassing the Shiga toxin genes (stxAB) . WRSd1 was constructed from S . dysenteriae 1 strain 1617 that was originally isolated during the 1968 to 1969 epidemic of Shiga dysentery in Guatemala . The virG(icsA) deletion was constructed from a streptomycin-resistant (Str(r)) mutant of 1617 by a filter mating procedures using a virG(icsA) deletion derivative, pDeltavirG2 . A colony that was invasive for HeLa cells and negative for the virG(icsA) gene by Southern blotting was grown anaerobically on plates containing chlorate for selection of resistant colonies that had lost the entire Shiga toxin gene . A virG(icsA) stxAB Str(r) mutant selected from the chlorate plates was designated WRSd1 . This candidate vaccine was evaluated for safety, immunogenicity, and protective efficacy using the guinea pig keratoconjunctivitis model . WRSd1 was Sereny negative, and two applications of this strain to the cornea elicited a significant protective immune response against the S . dysenteriae 1 O antigen . Vaccination with WRSd1 conferred protection against challenge with each of three virulent S . dysenteriae 1 strains . Since a vaccine protecting against multiple Shigella species is required for most areas where Shigella is endemic, protection studies using a combination vaccine of Shigella sonnei vaccine strain WRSS1, Shigella flexneri 2a vaccine strain SC602, and WRSd1 were also performed . Guinea pigs vaccinated with a mixture of equal amounts of the three vaccine strains were protected against challenge with each of the homologous virulent strains . Unlike WRSS1 and SC602, however, the level of protection afforded by WRSd1 in a combination vaccine was lower than the protection elicited by a pure culture . A current Good Manufacturing Practice product of WRSd1 given intragastrically to rhesus monkeys proved safe and immunogenic.

Med Microbiol Immunol (Berl), 2002 Mar, 190(4), 173 - 8
Enhancement of pentylenetetrazole-induced seizures by Shigella dysenteriae in LPS-resistant C3H/HeJ mice: role of the host response; Yuhas Y et al.; Convulsions and encephalopathy are common complications of Shiga toxin (Stx)-producing Shigella and enterohemorrhagic Escherichia coli infections . In previous studies, we demonstrated that Stx and lipopolysaccharide (LPS) act in concert to enhance mice sensitivity to pentylenetetrazole (PTZ)-induced seizures via mechanisms involving tumor necrosis factor alpha (TNFalpha), interleukinl beta and nitric oxide . To further elucidate the role of the host response in Shigella-related seizures, we studied the ability of Shigella dysenteriae and its products to modulate seizures in C3H/HeJ (lps(d/d)) and in C3H/HeN (lps(n/n) mice . Injection of S . dysenteriae 60R sonicate elevated plasma TNFalpha and enhanced the convulsive response to PTZ in both mouse strains . Induced TNFalpha levels were markedly lower in LPS-hyporesponsive C3H/HeJ mice than in LPS- responsive C3H/HeN mice: 7.4 ng/ml vs 44 ng/ml (induced by 4LD50) . Accordingly, a higher dose of S . dysenteriae sonicate was needed to sensitize the C3H/HeJ mice to seizures . Stx or LPS alone did not enhance seizures in either strain . Stx together with LPS enhanced seizures in LPS-responsive mice, but not in LPS-hyporesponsive mice in which they induced only a minor elevation in TNFalpha levels (1.5 ng/ml) . As compared to LPS-responsive mice, the LPS-hyporesponsive mice were less susceptible to the lethal effects of Shigella sonicate and were resistant to the lethal effect of purified Stx with LPS . These results demonstrate the crucial role of the host response with regard to the sensitivity to to LPS, and specifically TNFalpha production, in Shigella lethality and Shigella-related seizures.

Biosci Biotechnol Biochem, 2002 Mar, 66(3), 604 - 12
Rhamnose-binding lectins from steelhead trout (Oncorhynchus mykiss) eggs recognize bacterial lipopolysaccharides and lipoteichoic acid; Tateno H et al.; The interaction between bacteria and three L-rham-nose-binding lectins, named STL1, STL2, and STL3, from steelhead trout (Oncorhynchus mykiss) eggs was investigated . Although STLs bound to most Gram-negative and Gram-positive bacteria, they agglutinated only Escherichia coli K-12 and Bacillus subtilis among the bacteria tested . The binding was inhibited by L-rhamnose . STLs bound to distinct serotypes of lipopolysaccharides (LPSs), and showed much higher binding activities to smooth-type LPSs of Escherichia coli K-12 and Shigella flexneri 1A than to their corresponding rough-type LPSs . STLs also bound to lipoteichoic acid (LTA) of Bacillus subtilis . These results indicate that STLs bound to bacteria by recognizing LPSs or LTA on the cell surfaces.

Epidemiol Infect, 2002 Apr, 128(2), 131 - 8
Incidence and molecular analysis of Vibrio cholerae associated with cholera outbreak subsequent to the super cyclone in Orissa, India; Chhotray GP et al.; An epidemiological study was carried out to find out the aetiological agent for diarrhoeal disorders in the cyclone and flood affected areas of Orissa, India . Rectal swabs collected from 107 hospitalized diarrhoea patients were bacteriologically analysed to isolate and identify the various enteropathogens . Detection of toxic genes among E . coli and V . cholerae was carried out by polymerase chain reaction (PCR) assay . Of the 107 rectal swabs analysed, 72.3% were positive for V . cholerae O1 Ogawa, 7.2% for V . cholerae O139, 1.2% for E . coli (EAggEC) and 1.2% for Shigella flexneri type 6 . Using multiplex PCR assay it was found that all V . cholerae isolates were ctxA positive and El Tor biotype . Strains of V . cholerae O1 were observed to be resistant to nalidixic acid, furazolidone, streptomycin, co-trimoxazole and ampicillin . Except for nalidixic acid, the resistance pattern for O139 was identical to that of O1 strains . Representative strains of V . cholerae were further characterized by randomly amplified polymorphic DNA (RAPD) analysis and ribotyping . Both O1 and O139 V . cholerae strains exhibited the R3 pattern of ribotype and belonged to a similar pattern of RAPD compared with that of Calcutta strains . Early bacteriological and epidemiological investigations have revealed the dominance of V . cholerae O1 among the hospitalized patients in cyclone affected areas of Orissa . Drinking water scarcity and poor sanitation were thought to be responsible for these diarrhoeal outbreaks . Timely reporting and implementation of appropriate control measures could contain a vital epidemic in this area.

East Afr Med J, 2001 Jun, 78(6), 296 - 9
Antibiotic resistance and sero-groups of shigella among paediatric out-patients in southwest Ethiopia; Mache A; OBJECTIVE: To determine the prevalence of Shigella sero-groups and resistance pattern of isolates to commonly used antibiotics in Jimma . DESIGN: Cross-sectional survey . SETTING: The study was conducted in Jimma, southwest Ethiopia . SUBJECTS: A total of 384 paediatric out-patients with diarrhoea aged 14 years and below were studied . METHODS: Stool specimens were collected from children presenting with diarrhoea using Cary-Blair transport medium and buffer treated swabs from Jimma hospital and Jimma health centre . Isolation, biochemical characterisation, sero-grouping and antibiotic sensitivity testing were performed according to standard methodology in the Microbiology laboratory of Jimma University . RESULTS: Out of the 77 Shigella strains isolated, sero-group A comprised 29.9%, B 40.3%, C 19.5% and D 10.4% . Among all Shigella sero-groups, highest resistance was encountered to tetracycline (63.6%), ampicillin (70.1%), cephalothin (57.1%), trimethoprim-sulphamethoxazole (32.5%) and chloramphenicol (40.3%) whileleast resistance was observed to gentamicin (1.3%), polymyxin B (3.9%) and nalidixic acid (6.5%) . CONCLUSION: Gentamicin, polymyxin B and nalidixic acid were found to be the drugs of choice for cases related with shigellosis.

J Appl Microbiol, 2002, 92 Suppl, 136S - 43S
Quantitative assessment of risk reduction from hand washing with antibacterial soaps; Gibson LL et al.; The Centers for Disease Control and Prevention have estimated that there are 3,713,000 cases of infectious disease associated with day care facilities each year . The objective of this study was to examine the risk reduction achieved from using different soap formulations after diaper changing using a microbial quantitative risk assessment approach . To achieve this, a probability of infection model and an exposure assessment based on micro-organism transfer were used to evaluate the efficacy of different soap formulations in reducing the probability of disease following hand contact with an enteric pathogen . Based on this model, it was determined that the probability of infection ranged from 24/100 to 91/100 for those changing diapers of babies with symptomatic shigellosis who used a control product (soap without an antibacterial ingredient), 22/100 to 91/100 for those who used an antibacterial soap (chlorohexadine 4%), and 15/100 to 90/100 for those who used a triclosan (1.5%) antibacterial soap . Those with asymptomatic shigellosis who used a non-antibacterial control soap had a risk between 49/100,000 and 53/100, those who used the 4% chlorohexadine-containing soap had a risk between 43/100,000 and 51/100, and for those who used a 1.5% triclosan soap had a risk between 21/100,000 and 43/100 . The adequate washing of hands after diapering reduces risk and can be further reduced by a factor of 20% by the use of an antibacterial soap . Quantitative risk assessment is a valuable tool in the evaluation of household sanitizing agents and low risk outcomes.

J Immunol, 2002 May 15, 168(10), 5240 - 51
Two msbB genes encoding maximal acylation of lipid A are required for invasive Shigella flexneri to mediate inflammatory rupture and destruction of the intestinal epithelium; D'Hauteville H et al.; Shigella flexneri is a Gram-negative pathogen that invades and causes inflammatory destruction of the human colonic epithelium, thus leading to bloody diarrhea and dysentery . A type III secretion system that delivers effector proteins into target eukaryotic cells is largely responsible for cell and tissue invasion . However, the respective role of this invasive phenotype and of lipid A, the endotoxin of the Shigella LPS, in eliciting the inflammatory cascade that leads to rupture and destruction of the epithelial barrier, was unknown . We investigated whether genetic detoxification of lipid A would cause significant alteration in pathogenicity . We showed that S . flexneri has two functional msbB genes, one carried by the chromosome (msbB1) and the other by the virulence plasmid (msbB2), the products of which act in complement to produce full acyl-oxy-acylation of the myristate at the 3' position of the lipid A glucosamine disaccharide . A mutant in which both the msbB1 and msbB2 genes have been inactivated was impaired in its capacity to cause TNF-alpha production by human monocytes and to cause rupture and inflammatory destruction of the epithelial barrier in the rabbit ligated intestinal loop model of shigellosis, indicating that lipid A plays a significant role in aggravating inflammation that eventually destroys the intestinal barrier . In addition, neutralization of TNF-alpha during invasion by the wild-type strain strongly impaired its ability to cause rupture and inflammatory destruction of the epithelial lining, thus indicating that TNF-alpha is a major effector of epithelial destruction by Shigella.

Eur J Immunol, 2002 May, 32(5), 1464 - 71
Cytotoxicity and interleukin-1beta processing following Shigella flexneri infection of human monocyte-derived dendritic cells; Edgeworth JD et al.; Shigella flexneri infection of macrophages (MPhi) leads to activation of caspase-1 by the IpaB virulence factor, which induces rapid cell death and release of mature IL-1beta . Here we show that S . flexneri infection of human monocyte-derived dendritic cells (DC) also results in rapid IpaB-dependent death . Cytotoxicity is only partially blocked by the caspase-1 inhibitor YVAD, but completely blocked by the pan-caspase inhibitor z-VAD . Cytotoxicity is also partially blocked by glycine without affecting caspase-1-dependent IL-1beta processing, and treatment with glycine and YVAD completely blocks cytotoxicity, implying that glycine inhibits a caspase-1-independent cytotoxic mechanism . S . flexneri infection of LPS-pre-treated DC and Mphi results in comparable release of mature IL-1beta, although DC release significantly less IL-18 than MPhi . IL-1beta release from infected DC occurs within 3 h of the initial LPS pre-stimulation signal, implying that infection of DC will contribute towards induction of the early inflammatory response . The rapid death of DC during the early stages of shigellosis is likely to have adverse consequences for generation of adaptive immunity.

Cell Motil Cytoskeleton, 2002 Apr, 51(4), 187 - 96
Quantification of Shigella IcsA required for bacterial actin polymerization; Magdalena J et al.; Shigella move through the cytoplasm of host cells by active polymerization of host actin to form an "actin tail." Actin tail assembly is mediated by the Shigella protein IcsA . The process of Shigella actin assembly has been studied extensively using IcsA-expressing Escherichia coli in cytoplasmic extracts of Xenopus eggs . However, for reasons that have been unclear, wild type Shigella does not assemble actin in these extracts . We show that the defect in actin assembly in Xenopus extracts by Shigella can be rescued by increasing IcsA expression by approximately 3-fold . We calculate that the number of IcsA molecules required on an individual bacterium to assemble actin filaments in extracts is approximately 1,500-2,100 molecules, and the number of IcsA molecules required to assemble an actin tail is approximately 4,000 molecules . The majority of wild type Shigella do not express these levels of IcsA when grown in vitro . However, in infected host cells, IcsA expression is increased 3.2-fold, such that the number of IcsA molecules on a significant percentage of intracellular wild type Shigella would exceed that required for actin assembly in extracts . Thus, the number of IcsA molecules estimated from our studies in extracts as being required on an individual bacterium to assemble actin filaments or an actin tail is a reasonable prediction of the numbers required for these functions in Shigella-infected cells .

Mol Genet Genomics, 2002 Apr, 267(2), 171 - 8 Epub 2002 Feb 27.
Characterization of pECL18 and pKPN2: a proposed pathway for the evolution of two plasmids that carry identical genes for a Type II restriction-modification system; Zakharova MV et al.; The primary structures of the plasmids pECL18 (5571 bp) and pKPN2 (4196 bp) from Escherichia coli and Klebsiella pneumoniae, respectively, which carry genes for a Type II restriction-modification system (RMS2) with the specificity 5'-CCNGG-3', were determined in order to elucidate the structural relationship between them . The data suggest a possible role for recombination events at bom (basis of mobility) regions and the sites of resolution of multimer plasmid forms (so-called cer sequences) in the structural evolution of multicopy plasmids . Analysis of the sequences of pECL18 and pKPN2 showed that the genes for RM* Ecl18kI and RM* Kpn2kI, and the sequences of the rep (replication) regions in the two plasmids, are almost identical . In both plasmids, these regions are localized between the bom regions and the cer sites . The rest of the pECL18 sequence is almost identical to that of the mob (mobilization) region of ColE1, and the corresponding segment of pKPN2 is almost identical to part of pHS-2 from Shigella flexneri . The difference in primary structures results in different mobilization properties of pECL18 and pKPN2 . The complete sequences of pECL18, pKPN2 and the pairwise comparison of the sequences of pECL18, pKPN2, ColE1 and pHS-2 suggest that plasmids may exchange DNA units via site-specific recombination events at bom and cer sites . In the course of BLASTN database searches using the cer sites of pECL18 and pKPN2 as queries, we found twenty cer sites of natural plasmids . Alignment of these sequences reveals that they fall into two classes . The plasmids in each group possess related segments between their cer and bom sites.

Appl Environ Microbiol, 2002 May, 68(5), 2580 - 3
Rapid detection of Shigella species in environmental sewage by an immunocapture PCR with universal primers; Peng X et al.; In the present study, we developed a quick, highly specific method for detection of Shigella species by combining immunocapturing of the bacteria and a universal primer PCR . The method drastically enhances test sensitivity, and it can be used not only for identification of Shigella species in the environment but also for rapid detection of other pathogens.

Appl Environ Microbiol, 2002 May, 68(5), 2316 - 25
Genomic subtraction to identify and characterize sequences of Shiga toxin-producing Escherichia coli O91:H21; Pradel N et al.; To identify Shiga toxin-producing Escherichia coli genes associated with severe human disease, a genomic subtraction technique was used with hemolytic-uremic syndrome-associated O91:H21 strain CH014 and O6:H10 bovine strains . The method was adapted to the Shiga toxin-producing E . coli genome: three rounds of subtraction were used to isolate DNA fragments specific to strain CH014 . The fragments were characterized by genetic support analysis, sequencing, and hybridization to the genome of a collection of Shiga toxin-producing E . coli strains . A total of 42 fragments were found, 19 of which correspond to previously identified unique DNA sequences in the enterohemorrhagic E . coli EDL933 reference strain, including 7 fragments corresponding to prophage sequences and others encoding candidate virulence factors, such a SepA homolog protein and a fimbrial usher protein . In addition, the subtraction procedure yielded plasmid-related sequences from Shigella flexneri and enteropathogenic and Shiga toxin-producing E . coli virulence plasmids . We found that lateral gene transfer is extensive in strain CH014, and we discuss the role of genomic mobile elements, especially bacteriophages, in the evolution and possible transfer of virulence determinants.

Mol Microbiol, 2002 Mar, 43(6), 1543 - 53
Regulation of transcription by the activity of the Shigella flexneri type III secretion apparatus; Mavris M et al.; The virulence plasmid-encoded type III secretion system of Shigella flexneri consists of the Mxi-Spa secretion apparatus, secreted proteins IpaA-D and IpgD involved in entry of bacteria into epithelial cells,cytoplasmic chaperones IpgC and IpgE and 15 other secreted proteins of unknown function, including VirA and members of the IpaH family . The activity of the Mxi-Spa apparatus is regulated by external signals, and transcription of virA and IpaH genes is specifically induced in conditions of active secretion.We present genetic evidence that regulation of these genes involves both MxiE, the transcriptional activator of the AraC family encoded by the mxi operon, and IpgC, the chaperone for IpaB and IpaC . We also show that together MxiE and IpgC are sufficient to activatevirA and IpaH 9.8 promoters in Escherichia coli . InS . flexneri, increasing the expression of IpgC led to a concomitant increase in IpaH production in conditions of non-secretion . This suggests that the activity of secretion is sensed by the presence of free IpgC, which acts as a coactivator to allow MxiE to activate transcription at its target promoters.

Scand J Immunol, 2002 Apr, 55(4), 414 - 23
Delayed and reduced adaptive humoral immune responses in children with shigellosis compared with in adults; Raqib R et al.; We hypothesized that increased susceptibility to Shigella infection, increased severity of disease and high mortality in children compared with adults were consequences of insufficient adaptive immune responses . Antigen-specific immune responses were studied in paediatric patients (n = 38, 2-10 years) with shigellosis and compared with those of adult patients (n = 30, 18-45 years) . Peak frequencies of antigen (invasion plasmid coded antigen B, Ipa-B; lipopolysaccharide, LPS)-specific immunoglobulin (IgM)-antibody secreting cells (ASC) were seen within 3-5 days after the onset of diarrhoea in children, while peak IgA- and IgG-ASCs were obtained 8-10 days later in line with adults . Antigen-specific ASC responses in children ranged between 2 and 4% of the total ASC responses, in contrast to 8-15% in adults . The kinetics of LPS-specific IgG subclass titres was different in younger children (2.5-5 years) (IgG1 > IgG2 > IgG4 > IgG3) compared with in older children (6-8 years) (IgG2 > IgG1 >IgG3 > IgG4) and adults . Secretory IgA levels in stool peaked 8-10 days after onset in both adults and children . However, a rapid induction of stool LPS-specific IgA, IgA1 and IgA2 occurred in adult patients within 3-5 days of onset, while in children, this was delayed by 8-10 days . Similarly, higher number of tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma expressing cells in vitro were seen in adult patients in response to antigens (LPS and Ipa-B) in the acute stage in contrast to paediatric patients . Thus, paediatric patients with shigellosis have reduced and delayed adaptive immune responses compared with adult patients.

Mol Microbiol, 2002 Mar, 43(6), 1533 - 42
Spa15 of Shigella flexneri, a third type of chaperone in the type III secretion pathway; Page AL et al.; The type III secretion (TTS) pathway is used by numerous Gram-negative pathogens to inject virulence factors into eukaryotic cells . In addition to a functional TTS apparatus, secretion of effector proteins depends upon specific chaperones . Using a two-hybrid screen in yeast and a co-purification assay in Shigella flexneri, we demonstrated that Spa15, which is encoded by an operon for components of the TTS apparatus, is associated in the cytoplasm with three proteins that are secreted by the TTS pathway, IpaA, IpgB1 and OspC3 . Spa15 was found to be necessary for stability of IpgB1 but not IpaA, and for secretion of IpaA molecules that were stored in the cytoplasm but not those that were synthesized while the secretion apparatus was active . The ability of Spa15 to associate with several non-homologous secreted proteins, the presence of Spa15 homologues in other TTS systems and the location of the corresponding genes within operons for components of the TTS apparatus suggest that Spa15 belongs to a new class of TTS chaperones.

Cell Microbiol, 2002 Apr, 4(4), 223 - 33
Neural Wiskott-Aldrich syndrome protein (N-WASP) is the specific ligand for Shigella VirG among the WASP family and determines the host cell type allowing actin-based spreading; Suzuki T et al.; Shigella, the causative agent of bacillary dysentery, is capable of directing its movement within host cells by forming an actin comet tail . The VirG (IcsA) pro-tein expressed at one pole of the bacterium recruits neural Wiskott-Aldrich syndrome protein (N-WASP), a member of the WASP family, which in turn stimulates actin-related protein (Arp) 2/3 complex-mediated actin polymerization . As all the WASP family proteins induce actin polymerization by recruiting Arp2/3 complex, we investigated their involvement in Shigella motility . Here, we show that VirG binds to N-WASP but not to the other WASP family proteins . Using a series of chimeras obtained by swapping N-WASP and WASP domains, we demonstrated that the specificity of VirG to interact with N-WASP lies in the N-terminal region containing the pleckstrin homology (PH) domain and calmodulin-binding IQ motif of N-WASP . A conformational change in N-WASP was important for the VirG-N-WASP interaction, as elimination of the C-terminal acidic region, which is responsible for the intramolecular interaction with the central basic region of N-WASP, affected the specific binding to VirG . We observed that, in haematopoietic cells such as macrophages, polymorphonuclear leucocytes (PMNs) and platelets, WASP was predominantly expressed, whereas the expression of N-WASP was greatly suppressed . Indeed, unlike Listeria, Shigella was unable to move in macrophages at all, although the movement was restored as N-WASP was expressed ectopically . Thus, our findings demonstrate that N-WASP is a specific ligand of VirG, which determines the host cell type allowing actin-based spreading of Shigella.

Eur J Epidemiol, 2001, 17(6), 533 - 8
A large outbreak of Shigella sonnei gastroenteritis associated with consumption of fresh pasteurised milk cheese; Garcia-Fulgueiras A et al.; A large outbreak of Shigella sonnei gastroenteritis occurred in Murcia Region (Southeast Spain) in the winter of 1995-1996 . More than 200 people were affected . Epidemiological investigations implicated a regionally manufactured fresh pasteurised milk cheese as the vehicle of infection . A case-control study showed a statistically significant association between the illness and consumption of the suspect cheese . The dispersed sale of the cheese resulted in a regional dissemination of the organism and people were affected in eight townships . Research suggested that an infected foodhandler at the cheese factory might have been the source of contamination and that the processing method might have allowed cross-contamination to occur . This study emphasises the importance of increasing the control of strict hygiene during the processing of fresh cheese, since legislation does not forbid direct contact by hand that could result in contamination of cheese even when the milk pasteurisation process was correctly performed.

J Environ Health, 2001 Nov, 64(4), 9 - 13, 26
A school waterborne outbreak involving both Shigella sonnei and Entamoeba histolytica; Chen KT et al.; In an outbreak of gastroenteritis affecting 730 students, Shigella sonnei and Entamoeba histolytica were isolated from the stool specimens of patients . Environmental investigations revealed the source of infection to be contamination of underground well water by sewage from a toilet . The outbreak ended with the closure of the well water supply . To avoid such problems, institutions and other groups that maintain their own wells, including schools and summer camps, need to be vigilant about maintenance and check for potential contamination.

Comp Med, 2001 Jun, 51(3), 224 - 9
Effects of buprenorphine on immunogenicity and protective efficacy in the guinea pig keratoconjunctivitis model (Sereny test); Hanson CE et al.; Shigellosis is a disease of global proportions, with an estimated 164.7 million episodes annually throughout the world as well as an estimated 1.1 million associated mortalities in developing countries . Due to increasing incidence, and continued emergence of multi-drug resistant strains, Shigella vaccine development is considered a top public health priority . The guinea pig keratoconjunctivitis model, the basis for the Sereny test, remains the most reliable in vivo indicator of virulence of Shigella strains and immunogenicity and protective efficacy of Shigella vaccine candidates . The model is effective in evaluating the ability of Shigella strains to invade the corneal epithelia of guinea pigs and spread to contiguous cells, with the more virulent strains causing ulcerative keratoconjunctivitis . However, analgesia is not routinely used to relieve this painful condition because of potential immunomodulation and confounding of experimental results . The objective of the study reported here was to evaluate use of buprenorphine hydrochloride as an analgesic during the Sereny test . Local and systemic immune responses were measured in guinea pigs given buprenorphine versus those responses in controls . Results of this study suggest that buprenorphine, administered at an analgesic dose of 0.05 mg/kg of body weight twice daily, can be successfully used with the model without significantly affecting immunologic evaluation of Shigella vaccine candidates . However, in buprenorphine-treated animals, there was a significant increase in the amount of mucopurulent ocular discharge, requiring frequent cleaning of the affected eyes . Additionally, animals treated with buprenorphine had significant reduction in body weight, in comparison with saline controls.

J Clin Microbiol, 2002 Apr, 40(4), 1538 - 40
Epidemic strains of Shigella sonnei biotype g carrying integrons; McIver CJ et al.; Class 2 integrons (Tn7) were found in all randomly selected epidemic (n = 27) and preepidemic (n = 13) strains of multiresistant Shigella sonnei biotype g . A class 1 integron was also found in two epidemic strains . Gene cassettes within these integrons account for resistance to commonly used therapeutic agents.

Mol Microbiol, 1997 Jul, 25(1), 107 - 15
The Escherichia coli K-12 sheA gene encodes a 34-kDa secreted haemolysin; del Castillo FJ et al.; Haemolytic toxins belong to one of several classes of virulence factors that contribute to bacterial pathogenicity . The non-pathogenic Escherichia coli K-12 laboratory strain was considered for years to be non-haemolytic . However, overproduction of several transcriptional regulators induced the appearance of a haemolytic activity that is absent under usual laboratory growth conditions . In this work, we have cloned and characterized an E . coli K-12 gene, sheA, whose overexpression results in a haemolytic phenotype . It maps to min 27 on the genetic map, and codes for a 34-kDa polypeptide with at least one putative transmembrane segment . This polypeptide, which has neither signal peptide nor other known secretory motifs, is secreted to the medium during the exponential growth phase . In vitro coupled transcription/translation assays, using a plasmid carrying only the sheA gene as template, resulted in the production of a polypeptide with haemolytic activity per se . Our results demonstrate that the sheA gene actually encodes the E . coli K-12 chromosomal haemolysin . The SheA haemolysin does not resemble other known cytolytic toxins, and it may represent the prototype of a novel family, as suggested by the presence of homologues in several E . coli pathogenic strains and in Shigella flexneri.

Antimicrob Agents Chemother, 2002 Apr, 46(4), 1038 - 45
Genetic determinants of tetracycline resistance in Vibrio harveyi; Teo JW et al.; Isolates of Vibrio harveyi, a prawn pathogen, have demonstrated multiple antibiotic resistance to commonly used antimicrobial agents, such as oxytetracycline . In this paper, we describe the cloning and characterization of two tetracycline resistance determinants from V . harveyi strain M3.4L . The first resistance determinant, cloned as a 4,590-bp fragment, was identical to tetA and flanking sequences encoded on transposon Tn10 from Shigella flexneri . The second determinant, cloned as a 3,358-bp fragment in pATJ1, contains two open reading frames, designated tet35 and txr . tet35 encodes a 369-amino-acid protein that was predicted to have nine transmembrane regions . It is a novel protein which has no homology to any other drug resistance protein but has low levels of homology (28%) to Na(+)/H(+) antiporters . Transposon mutagenesis showed that tet35 and txr were required for tetracycline resistance in a heterologous Escherichia coli host . Tetracycline accumulation studies indicate that E . coli carrying tet35 and txr can function as an energy-dependent tetracycline efflux pump but is less efficient than TetA.

Bull Soc Pathol Exot, 2001 Dec, 94(5), 401 - 2
{Salubrity of ice sold in blocks: from production to sales}; Agbessi TK et al.; We conducted a study in order to determine the salubrity of ice produced in blocks, tracing them from 10 factories in Abidjan to 10 different market places where they are sold in town . On the basis of physico-chemical and microbiological analyses, the water was shown to be potable . However, the results of the analysed samples taken from the ice indicated a deterioration of the physico-chemical and microbiological qualities . The data revealed that consumers may be exposed to water-borne diseases such as cholera, salmonelloses, shigelloses, gastro-enteritis . Ice producers and vendors must be provided with special training in sanitation so as to prevent the transmission of pathogenic bacteria in ice.

Infection, 2002 Jan, 30(1), 3 - 6
Norwalk virus gastroenteritis among Israeli soldiers: lack of evidence for flyborne transmission; Cohen D et al.; BACKGROUND: Paired sera collected from subjects before and after a fly-control intervention trial conducted in the Israel Defense Force (IDF) were tested for seroconversion to Norwalk virus (NV) to examine the role of NV as a cause of diarrhea in this population and to ascertain whether flies might also be implicated in transmission . MATERIALS AND METHODS: An enzyme-linked immunosorbent assay (ELISA), using recombinant NV capsid proteins (rNV) as antigen was employed to determine the seroconversion rate in a sample of 444 subjects . RESULTS: During 11-week field training cycles, 18% of IDF soldiers who were tested had an NV infection defined as a > or = 4-fold rise in antibody, yielding a cumulative incidence of nearly one infection (0.95) per soldier per year . The rate of seroconversion was nearly twice as high among soldiers who recalled having diarrhea as among those who did not, but the rates did not differ significantly between soldiers in the fly intervention areas and those in the control areas . CONCLUSION: NV is a common cause of enteric infections and diarrhea among Israeli soldiers who serve under field conditions, but unlike infections with Shigella and enterotoxigenic Escherichia coli, transmission of NV cannot be interrupted with an aggressive program of fly-control.

Clin Microbiol Infect, 1996 Aug, 2(1), 55 - 58
Rapid and sensitive detection of Shigella sonnei in feces by the use of an O-antigen-specific monoclonal antibody in a combined immunomagnetic separation-polymerase chain reaction assay; Achi-Berglund R et al.; OBJECTIVE: The aim of the present work was to develop a rapid, specific and highly sensitive diagnostic method for the detection of Shigella sonnei directly from stool samples . DESIGN AND METHODS: An immunomagnetic separation-polymerase chain reaction (IMS-PCR) combined assay for diagnosis of S . sonnei was developed . For this, a monoclonal antibody (Mab) specific for the O-antigen of S . sonnei was coated to magnetic beads for capture, concentration and separation of S . sonnei from feces . Bacterial DNA, was amplified by the PCR with specific primers . The amplified products were developed by dot blot hybridization with a specific alkaline phosphatase-conjugated probe . RESULTS: The purified MASS MAb reacted specifically with the Plesiomonas shigelloides (the same O-antigen as Shigella sonnei) LPS . The primers were specific for invasive Shigella and enteroinvasive Escherichia coli . Only invasive Shigella sonnei strains gave a positive result in the IMS-PCR assay . The detection limit was 10 to 15 c.f.u . CONCLUSIONS: The availability of IMS-PCR assays provides an improved method for the diagnosis of shigellae directly from feces . The assay is rapid, highly sensitive and specific for the detection of Shigella sonnei directly from stool samples.

J Infect Dis, 2002 Feb 15, 185(4), 497 - 502 Epub 2002 Jan 22.
Prevalence of enteric pathogens among international travelers with diarrhea acquired in Kenya (Mombasa), India (Goa), or Jamaica (Montego Bay); Jiang ZD et al.; Stools from tourists from Europe and North America who acquired diarrhea in Mombasa (Kenya), Goa (India), or Montego Bay (Jamaica) were examined for enteric pathogens . Enterotoxigenic Escherichia coli (ETEC) was the most common pathogen (25%) identified in the 3 locations . Isolation of Shigella species was more frequent in Goa and Mombasa than in Montego Bay (10%, 9%, and 0.3%, respectively; P <.005) . Viruses (rotaviruses and enteric adenoviruses) were found in 9% of travelers to the 3 areas . Of 275 ETEC isolates in this study, 158 (57%) produced a defined colonization factor antigen (CFA) . Coli surface 6 (CS6) was the most frequent and was found in 41%-52% of CFA/CS-positive ETEC isolates . The frequency of resistance among bacterial enteropathogens to traditional antimicrobial agents was particularly high throughout the study period in all 3 regions . Quinolones were active against the bacterial enteropathogens in the 3 sites.

Curr Biol, 2002 Feb 19, 12(4), 341 - 5
Cdc42 facilitates invasion but not the actin-based motility of Shigella; Shibata T et al.; The enteric pathogen Shigella utilizes host-encoded proteins to invade the gastrointestinal tract . Efficient invasion of host cells requires the stimulation of Rho-family GTPases and cytoskeletal alterations by Shigella-encoded IpaC . Following invasion and lysis of the phagosome, Shigella exploits the host's actin-based polymerization machinery to assemble an actin tail that serves as the propulsive force required for spreading within and between cells . The Shigella surface protein IcsA stimulates actin-tail formation by recruiting host-encoded N-WASP to drive Arp2/3-mediated actin assembly . N-WASP is absolutely required for Shigella motility, but not for Shigella invasion . Although Rho-family GTPases have been implicated in both the invasion and motility of Shigella, the role of Cdc42, an N-WASP activator, in this process has been controversial . In these studies, we have examined the role of Cdc42 in Shigella invasion and actin-based motility using Cdc42-deficient cells . We demonstrate that Cdc42 is required for efficient Shigella invasion but reveal a minor Cdc42-independent pathway that can permit Shigella invasion . However, the actin-based motility of Shigella, as well as vaccinia, proceeds unperturbed in the absence of Cdc42 . These data further support the involvement of distinct host-encoded proteins in the steps regulating invasion and intercellular spread of Shigella.

Sante, 2001 Oct-Dec, 11(4), 217 - 9
{Investigation of a shigellosis outbreak in a rural zone of Senegal}; Diallo A et al.; The investigation of this outbreak took place in Niakhar (IRD project study area), a rural area located 150 km East of Dakar . Covering 30 villages, with a population of about 30,000 inhabitants, the area has been under demographic and epidemiological surveillance . In 1999, the surveillance allowed 973 cases of shigellosis to be recorded out of 1,751 cases of dysenteric diarrhoeas . The outbreak reached a peak during the raining season (73% of the cases in September and October) . All the villages and all age groups were concerned . The attack rate in the population was 3% . During the same period, 22 deaths were attributed to shigellosis, leading to a lethality of 2.3% . Children under five were the most affected . The bacteriological examination isolated S . flexneri in 72% of 12 stools samples and S . dysenteriae A1 (SD1) in 14% . All serotypes were resistant to ampicillin and susceptible to quinolones . Susceptibility to cotrimoxazole was unconstant . Apart from the usual factors involved in the spread of diarrhoeas, the main reason evoked to explain the duration of the epidemic has been the lack of adequate emergency antibiotherapy treatment . Quinolones, recommended by the health authorities, could not be provided by health services . The identification of the SD1 serotype confirmed its involvement in the outbreak of shigellosis . The exact role of S . flexneri in shigellosis epidemics should be further studied.

Zhonghua Liu Xing Bing Xue Za Zhi, 2001 Feb, 22(1), 46 - 8
{Study on diarrhea disease and Escherichia coli strains harboring HPI pathogenicity island of Yersinia enterolitica in Shandong province}; Cui S et al.; OBJECTIVE: It was found that some E . coli strains previously identified as entero SLTs-producing and invasive E . coli (ESIEC), harboring HPI pathogenicity island of Yersinia enterolitica . This research was designed to reveal prevalence, susceptible group and clinical features it caused . METHODS: All of the diarrhea patients were from the out-patient units of four hospitals in Shandong province from June to November of 1997 . Stool specimen were collected before administration of antibiotics for isolation of enteric bacterial pathogen . Clinical symptoms were recorded at the same time . RESULTS: A total number of 449 enteric pathogenic bacteria strains were detected among stool samples from 671 patients, with isolation rates of Shigella species and diarrheagenic E . coli 25.48% and 15.05% respectively . When irp-2 and ipaB gene fragments were used as DNA probes, 42 of 176 un-identifiable strains were found irp-2(+) and ipaB(-), which were identified as HPI-harboring E . coli . Typical symptoms of the diarrhea caused by HPI-harboring E . coli were described as mild, including abdominal pain, shiver and vapidity . Temperature of the patients was usually normal . Over 6 times of bowel movements per day was frequently observed, of which most were unformed stools with mucous . CONCLUSION: HIP-harboring E . coli was an important diarrheagenic pathogen identified from 671 patients with diarrhea . Shigella was found to be the majority strain.

Zhonghua Liu Xing Bing Xue Za Zhi, 2000 Aug, 21(4), 280 - 2
{Gena types of Shigella enterotoxins of S . flexneri 2a}; Bai S et al.; OBJECTIVE: To identify homogenous clones of S . flexneri 2a, using gene distribution polymorphism of Shigella enterotoxin 1 (set 1) and Shigella enterotoxin 2 (set 2) in a Shigellosis outbreak caused by S . flexneri 2a . METHODS: In addition to field epidemiological investigation, 43 strains of S . flexneri 2a were determined by polymerase chain reaction (PCR) . RESULTS: The 43 strains (1 from food, 1 from a carrier, 41 from patients) were divided into 3 clones (set1 +/set2 + for 39 strains, set1 -/set2 + for 1, set1 +/set2 - for 3 strains) . CONCLUSION: This outbreak was caused by S . flexneri 2a . The route of transmission was contaminated-food borne . Some sporadic cases were noticed during the outbreak . The method used in this study was satisfactory to the identification of S . flexneri 2a.

J Health Popul Nutr, 2001 Dec, 19(4), 331 - 5
Shigellocidal properties of three Nigerian medicinal plants: Ocimum gratissimum, Terminalia avicennoides, and Momordica balsamina; Iwalokun BA et al.; The prevalence of multidrug-resistant shigellae is an important concern in the treatment of shigellosis in many developing countries, and other therapies, including herbal agents, may provide an important alternative to antimicrobial agents . In this study, three Nigerian medicinal plants: Ocimum gratissimum, Terminalia avicennoides, and Momordica balsamina were investigated for their activities against multidrug-resistant Shigella species isolated from patients with bacilliary dysentery in Lagos . Decoctions of O . gratissimum and concoctions of O . gratissimum and T . avicennoides at crude concentration of 3,000 micrograms/mL markedly inhibited the growth of all isolates tested . Zones of inhibition indicating susceptibilities of the organisms varied from 18.3 to 21.5 mm for Shigella dysenteriae, 15.3 to 16.3 mm for S . flexneri, 18.8 to 19.3 mm for S . sonnei, and 16.5 mm for S . boydii . Except S . flexneri, minimum inhibitory concentration and minimum bactericidal concentration revealed a higher shigellocidal property of O . gratissimum/T . avicennoides concoction than other extracts in S . dysenteriae (300-515.6 vs 337.5-1,312.5 micrograms/mL), S . sonnei (309.4-543.8 vs 403.1-1,312.5 micrograms/mL), and S . boydii (243.8-337.5 vs 253-1,312.5 micrograms/mL) . O . gratissimum showed a greater shigellocidal effect against the S . flexneri isolates, while extracts of M . balsamina possessed low shigellocidal potential . The results suggest that aqueous extracts of O . gratissimum and T . avicennoides as decoctions and concoctions could be useful in the treatment of shigellosis and should be clinically evaluated specially in Nigerian region.

Infect Immun, 2002 Mar, 70(3), 1279 - 86
Cloned Shiga toxin 2 B subunit induces apoptosis in Ramos Burkitt's lymphoma B cells; Marcato P et al.; The Shiga toxins (Stx1 and Stx2), produced by Shigella dysenteriae type 1 and enterohemorrhagic Escherichia coli, consist of one A subunit and five B subunits . The Stx1 and Stx2 B subunits form a pentameric structure that binds to globotriaosylceramide (Gb3-Cer) receptors on eukaryotic cells and promotes endocytosis . The A subunit then inhibits protein biosynthesis, which triggers apoptosis in the affected cell . In addition to its Gb3-Cer binding activity, the data in the following report demonstrate that the Stx2 B pentamer induces apoptosis in Ramos Burkitt's lymphoma B cells independently of A subunit activity . Apoptosis was not observed in A subunit-free preparations of the Stx1 B pentamer which competitively inhibited Stx2 B pentamer-mediated apoptosis . The pancaspase inhibitor, Z-VAD-fmk, prevented apoptosis in Ramos cells exposed to the Stx2 B subunit, Stx1 or Stx2 . Brefeldin A, an inhibitor of the Golgi transport system, also prevented Stx2 B subunit-mediated apoptosis . These observations suggest that the Stx2 B subunit must be internalized, via Gb3-Cer receptors, to induce Ramos cell apoptosis . Moreover, unlike the two holotoxins, Stx2 B subunit-mediated apoptosis does not involve inhibition of protein biosynthesis . This study provides further insight into the pathogenic potential of this family of potent bacterial exotoxins.

Infect Immun, 2002 Mar, 70(3), 1150 - 8
Shigella flexneri Interactions with the Basolateral Membrane Domain of Polarized Model Intestinal Epithelium: Role of Lipopolysaccharide in Cell Invasion and in Activation of the Mitogen-Activated Protein Kinase ERK; Kohler H et al.; An early step governing Shigella flexneri pathogenesis is the invasion of the colonic epithelium from the basolateral surface followed by disruption of the colonic epithelial barrier . Despite recent insight into S . flexneri-host interactions, much remains to be determined regarding the nature of the initial contact between S . flexneri and the host epithelial basolateral membrane domain . Since the lipopolysaccharide (LPS) is located at the outermost part of the bacterial membrane, we considered that this component might be used by S . flexneri to attach to the basolateral surface of the intestinal epithelium and promote a proinflammatory response . Therefore, polarized human T84 intestinal epithelial cells were infected from the basolateral surface with either wild-type S . flexneri or one of its isogenic LPS-defective strains with mutations in either rfc, rfaL, or galU . We found that both adherence to and internalization into the basolateral surface of a polarized intestinal epithelium with S . flexneri were highly dependent on the length of the LPS (i.e., rfc > rfaL > galU) . Furthermore, the addition of the anti-inflammatory LPS (RsDPLA) considerably decreased the invasion profile of wild-type S . flexneri by nearly 50% . Since LPS is associated with host inflammation, we further examined whether this molecule was involved in Shigella-induced inflammatory events . We found that S . flexneri LPS plays an important role in mediating epithelial-derived signaling, which leads to directed migration of polymorphonuclear leukocytes across model intestinal epithelium . This signaling most likely involves the activation of the mitogen-activated protein kinase extracellular regulated kinase . Thus, our findings have important implications on the understanding of the mechanisms by which S . flexneri can elicit mucosal inflammation.

Acta Paediatr, 2001 Dec, 90(12), 1373 - 8
Hyperimmune bovine colostrum in the treatment of shigellosis in children: a double-blind, randomized, controlled trial; Ashraf H et al.; Immunological approaches have been considered as an alternative therapeutic option for the treatment of enteric infections over the past few years . Hyperimmune bovine colostrum (HBC) is a potentially innovative immunological option in the management of shigellosis together with traditional antibiotic therapy . Children aged 1-12 y with a history of bloody mucoid diarrhoea of less than 5 d duration were enrolled after their stool specimen was found to be positive for Shigella dysenteriae type I antigen by a rapid diagnostic fluorescent antibody staining test . They were randomized to receive either HBC containing very high titres of antibody against S . dysenteriae type I antigen or bovine colostrum (BC) without any antibody . The study group received 100 ml of HBC three times a day orally for 3 d and control group received BC . Children also received pivmecillinam in a dose of 50 mg kg(-1) d(-1) in four divided doses orally for 5 d . Admission characteristics of the 34 children in the HBC group and 35 in the BC group were comparable . No significant differences were observed in duration of diarrhoea, fever, anorexia, abdominal pain, tenesmus, stool frequency or visible blood in the stool between the groups . Two (6%) children in the study and five (14%) in the control group remained stool culture positive for S . dysenteriae type 1, even after 5 d of sensitive antimicrobial therapy . Conclusion: The results indicate that HBC as an adjuvant is unable to show any beneficial effect in reducing the stool frequency, duration or severity of childhood shigellosis due to S . dysenteriae type I infection.

FEBS Lett, 2002 Feb 13, 512(1-3), 8 - 12
Shigella apyrase--a novel variant of bacterial acid phosphatases?
Babu MM, Kamalakkannan S, Subrahmanyam YV, Sankaran K.
A virulence-associated ATP diphosphohydrolase activity in the periplasm of Shigella, identified as apyrase, was found to be markedly similar to bacterial non-specific acid phosphatases in primary structure . When the Shigella apyrase sequence was threaded in to the recently published 3D structure of the highly similar (73%) Escherichia blattae acid phosphatase it was found to have a highly overlapping 3D structure . Our analysis, which included assays for phosphatase, haloperoxidase and catalase activities, led us to hypothesize that Shigella apyrase might belong to a new class of pyrophosphatase originating as one more variant in the family of bacterial non-specific acid phosphatases . It revealed interesting structure-function relationships and probable roles relevant to pathogenesis.

J Biol Chem, 2002 May 3, 277(18), 15333 - 44 Epub 2002 Feb 15.
Molecular dissection of VirB, a key regulator of the virulence cascade of Shigella flexneri; Beloin C et al.; The VirB protein is a key regulator of virulence gene expression in the facultative enteroinvasive pathogen Shigella flexneri . While genetic evidence has shown that it is required for activation of transcription of virulence genes located on a 230-kb plasmid in this bacterium, hitherto, evidence that VirB is a DNA-binding protein has been lacking . Although VirB shows extensive homology to proteins involved in plasmid partitioning, it does not resemble any known conventional transcription factor . Here we show for the first time that VirB binds to the promoter regions of the virulence genes in vivo . We also show that VirB forms dimeric and higher oligomeric structures both in vivo and in vitro and that this property is independent of DNA binding . The oligomerization activity of VirB is distributed over two domains: a leucine zipper-like motif and a carboxyl-terminal domain likely to form triple coiled structures . VirB possesses a helix-turn-helix motif, which is required for DNA binding . The amino-terminal domain of the protein is also required for DNA binding and virulence gene activation . The possibility that VirB requires a co-factor for specific interaction with target promoters in vivo is discussed.

Mol Microbiol, 2002 Jan, 43(1), 207 - 15
Activation of Shiga toxin type 2d (Stx2d) by elastase involves cleavage of the C-terminal two amino acids of the A2 peptide in the context of the appropriate B pentamer; Melton-Celsa AR et al.; Shiga toxins (Stx) are potent ribosome-inactivating toxins that are produced by Shigella dysenteriae type 1 or certain strains of Escherichia coli . These toxins are composed of one A subunit that can be nicked and reduced to an enzymatically active A1(approximately 27 kDa) and an A2 peptide (approximately 4 kDa) as well as a pentamer of B subunits (approximately 7 kDa/monomer) that binds the eukaryotic cell . Purified Shiga toxin type 2d is activated 10- to 1000-fold for Vero cell toxicity by preincubation with mouse or human intestinal mucus or purified mouse elastase, whereas Stx2, Stx2c, Stx2e and Stx1 are not activatable . E . coli strains that produce the activatable Stx2d are more virulent in a streptomycin (str)-treated mouse model of infection {lethal dose 50% (LD50) = 101} than are E . coli strains that produce any other type of Stx (LD50 = 1010) . To identify the element(s) of Stx2d that are required for mucus-mediated activation, toxin genes were constructed such that the expressed mutant toxins consisted of hybrids of Stx2d and Stx1, Stx2 or Stx2e, contained deletions of up to six amino acids from the C-terminus of the A2 of Stx2d or were altered in one or both of the two amino acids of the A2 of Stx2d that represent the only amino acid differences between the activatable Stx2d and the non-activatable Stx2c . Analysis of these mutant toxins revealed that the A2 portion of Stx2d is required for toxin activation and that activation is abrogated if the Stx1 or Stx2e B subunit is substituted for the Stx2d B polypeptide . Furthermore, mass spectrometry performed on buffer- or elastase-treated Stx2d indicated that the A2 peptide of the activated Stx2d was two amino acids smaller than the A2 peptide from buffer-treated Stx2d . This finding, together with the toxin hybrid results, suggests that activation involves B pentamer-dependent cleavage by elastase of the C-terminal two amino acids from the Stx2d A2 peptide.

J Appl Microbiol, 2002, 92(2), 322 - 8
Isolation and preliminary characterization of bacteriocins produced by Vibrio vulnificus; Shehane SD et al.; AIMS: The aim of this work was to isolate bacteriocins from the environment that would be effective in neutralizing Vibrio vulnificus in seafood . METHODS AND RESULTS: Water samples from Wilmington (NC, USA) were plated to determine total viable counts and to isolate presumptive Vibrio spp . Isolates containing plasmids were checked for antimicrobial activity which was not due to lytic bacteriophage or small, non-specific molecules . Three bacteriocin producers were detected and their inhibitory spectra determined: IW1 inhibited few strains of V . vulnificus; BC1 inhibited several strains of V . vulnificus, V . cholerae and V . parahaemolyticus and BC2 inhibited all tested Vibrio spp., Plesiomonas shigelloides and Escherichia coli . Loss of inhibitory activity coincided with loss of the bacteriocinogenic plasmid . The bacteriocins were found to be between 1.3 and 9.0 kDa . IW1 was heat labile, while BC1 was moderately stable except at extreme temperatures . BC2 was very stable and maintained its activity when frozen, autoclaved or exposed to extreme pH values . CONCLUSIONS: Bacteriocins have been isolated from environmental isolates of V . vulnificus and V . cholerae . BC2, with its broad spectrum and stability, may be useful in neutralizing V . vulnificus . SIGNIFICANCE AND IMPACT OF THE STUDY: The results have significance in relation to reducing the occurrence of food poisoning caused by V . vulnificus.

Roum Arch Microbiol Immunol, 2000 Jan-Jun, 59(1-2), 103 - 17
Differentiation of Shigella strains by plasmid profile analysis, serotyping and phage typing; Surdeanu M et al.; Ninety-one Shigella flexneri and 29 Shigella sonnei strains isolated during 1994 from sporadic cases of shigellosis and healthy carriers were analyzed for plasmid profile in order to compare the discriminating ability of this method with that of serotyping and phage typing . Our study revealed 10 plasmid profiles (PP) among S . sonnei strains . A total of 26 out of 29 (89%) S . sonnei isolates could be placed into two phage types (type 1 and 20) comprising four PP for phage type 1 and seven PP for type 20, respectively . Twenty-three different PP were identified among S . flexneri strains . Each serotype was associated with a specific predominant plasmid profile, except serotype 2a . This serotype, the most frequently isolated in Romania, was still rather homogeneous: 33 out of 39 isolates belonged to phage type 125, 27 of which could be placed into two related PP (F10 and F17) . Comparison of plasmid patterns of epidemiologically independent S . flexneri serotype 2a isolates with those exhibited by 45 serotype 2a isolates associated to six independent outbreaks revealed the same homogeneity . Thirty-eight strains, representing 4 of 6 outbreaks, had F10 and F17 plasmid patterns . The discrimination indices (D) for plasmid profile analysis alone (D = 0.890) and for the combination of serotyping and phage typing (D = 0.841) indicate that both typing systems have a nearly similar ability of discriminating among S . flexneri strains . By combining the results of the three typing methods, a total of 42 types are distinguished and the D value is 0.942 . Our data suggest that plasmid profile analysis can complement phenotyping methods resulting in a degree of discrimination that cannot be achieved by either system alone.

Pediatr Infect Dis J, 2002 Feb, 21(2), 170 - 2
Chronic vulvovaginitis caused by antibiotic-resistant Shigella flexneri in a prepubertal child; Baiulescu M et al.; A 7-year 8-month-old girl was diagnosed with a prolonged course of vulvovaginitis caused by Shigella flexneri . The child was symptomatic with intermittent vaginal bleeding, dysuria and foul smelling vaginal discharge for a 3-year period . Initial attempts to resolve the infection with successive courses of antibiotic therapy using ampicillin, trimethoprim-sulfamethoxazole, cefixime and amoxicillin/clavulanic acid failed . The child's infection was finally resolved by a 14-day course of ciprofloxacin.

Int J STD AIDS, 2002 Feb, 13(2), 135 - 6
Shigella sonnei: another cause of sexually acquired reactive arthritis; Chen M et al.; We report a case of reactive arthritis attributable to sexually-acquired Shigella sonnei infection . This occurred in the context of an outbreak of S . sonnei among homosexually-active men in Sydney, Australia, in 2000.

World J Gastroenterol, 1999 Jun, 5(3), 245 - 248
Pathogenic effects of Opolysaccharide from Shigella flexneri strain; Zhong QP et al.; AIM:To investigate the specific pathogenesis of O-polysaccharide (O-PS) which is on the outer membrane of lipopolysaccharides (LPS) from Shigella flexneri.METHODS:The O-PS was isolated and purified from Shigella flexneri 5 M90T by enzymatic hydrolysis and gel chromatography . Effects of O-PS were observed by in vitro experiment, (HeLa cell culture), and in vivo experiment (rabbit ileal loop assay).RESULTS:In vitro and in vivo experiments with the purified O-PS from Shigella flexneri revealed that the O-PS alone was toxic to Hela cells and caused mucosal inflammation and hemorrhagic exudation in ileal loop of rabbit.DISCUSSION:O-PS might be one of the factors causing diarrhea and its mechanism was different from endotoxin reaction of LPS.The molecular mechanism of O-PS need further studies.

Ann Acad Med Singapore, 2001 Nov, 30(6), 668 - 70
Shigella septicaemia in adults: report of two cases and mini-review; Oh HM et al.; INTRODUCTION: We report 2 cases of Shigella septicaemia in adult patients . CLINICAL PICTURE: Two 57-year-old women presented with non-bloody diarrhoea and fever . The first patient was an inmate of a long-term care facility who was schizophrenic and the second patient was a diabetic who recently travelled to Medan, Indonesia . Both patients were febrile, hypotensive and dehydrated . The first patient was neutropenic, thrombocytopenic and had acute renal failure . Blood cultures yielded Shigella flexneri and stool cultures gave negative results for both patients . TREATMENT: Rehydration and intravenous ceftriaxone were instituted . OUTCOME: The patients' symptoms and hypotension resolved . CONCLUSION: Appropriate antibiotics can decrease the severity and duration of Shigella septicaemia.

AIDS Read, 2001 Dec, 11(12), 617 - 9
Case report . Epididymo-orchitis and bacteremia caused by Plesiomonas shigelloides in an HIV-infected patient; Young AZ et al.; Invasive infection and extraintestinal complications are rarely caused by Plesiomonas shigelloides, a waterborne bacterium implicated in gastroenteritis . Recent evidence from several reports suggests its importance in causing opportunistic infections in immunocompromised hosts . We report a case of P shigelloides bacteremia and epididymo-orchitis in a patient with HIV infection and chronic hepatitis C . This case illustrates a novel site of involvement by P shigelloides and underscores its role as an opportunistic pathogen.

Kansenshogaku Zasshi, 2001 Dec, 75(12), 1025 - 9
{Isolation of provisional serovars of Shigella in diarrheal cases of tourists}; Ueda Y et al.; Twenty-four Shigella strains of provisional serovars were isolated from travellers with diarrhea during 1993-2000 at Osaka Airport- and Kansai Airport-Quarantine Station . The outline of these cases were as follows . 1) The provisional serovars of these strains (number of cases) were S . dysenteriae 93-119 (2), S . dysenteriae 204/96 (4), S . dysenteriae I9809-73 (4), S . flexneri 88-893 (9), and S . boydii E16553 (5) . 2) Symptoms of these cases were diarrhea, abdominal pain, fever, and vomiting . The ratios of each symptom were 100%, 50%, 50%, and 29.2%, respectively . Typical dysentery symptoms (mucous and bloody stool) were observed in three cases . 3) In six cases (25.0%), plural kinds of entero-pathogenic bacteria were isolated, and in four cases, two kinds of Shigella serovar (known and unknown type) were isolated . 4) The major regions where these travellers were infected was South-west Asia (79.2%) . 5) Twenty-three of the Shigella strains (95.8%) of the provisional serovars were resistant to two or more drugs tested (SM, CP, TC, KM, ABPC, NA, and OFLX) . The most predominant drug resistance pattern was SM . CP . TC . ABPC.

J Basic Microbiol, 2001, 41(6), 367 - 74
Incidence of colicinogenic strains among human Escherichia coli; Smarda J et al.; During the years 1993-1999, altogether 1,043 Escherichia coli strains from colons of different persons were screened for colicinogeny using a most susceptible procedure and indicator system . In control persons (with healthy colons), 41.37% producers of colicins were found . In patients suffering from salmonelloses, the proportion of colicinogenic Escherichia coli was the same . In patients with non-specific inflammatory colon diseases, the proportion of colicinogenic Escherichia coli strains appeared slightly though weakly, significantly or unsignificantly increased: to 47.50% in morbus Crohn and to 56.10% in colitis ulcerosa . These results suggest some sort of engagement of colicinogeny in the pathogenesis thereof . In malignant tumours of the colon, the incidence of colicinogenic Escherichia coli was not altered (40.58%) . This does not indicate any colicin participation in the pathology of malignant tumours . In colitis ulcerosa, the incidence of colicinogenic Escherichia coli strains inhibiting Shigella sonei 17 (the indicator for colicin Js which generally inhibits interoinvasive strains of both species) increased from 21.94% (control samples) to 41.46% . Uropathogenic Escherichia coli strains shared the same incidence of colicinogeny as controls (42.08%), if they were not haemolytic; haemolytic ones were colicinogenic with only 22.37% . This difference was highly significant . The patterns of some colicin activities in the set of five indicator strains used suggested that several wild strains produced new, so far unknown types of colicins and/or combinations thereof.

Ther Drug Monit, 2001 Dec, 23(6), 647 - 9
Abrupt increase of tacrolimus blood levels during an episode of Shigella infection in a child after liver transplantation; Zylber-Katz E et al.; The authors report the case of an 8-year-old girl who underwent a liver transplant at the age of 18 months because of biliary atresia . She was treated with cyclosporin for more than 5 years . Increased hirsutism prompted a change to tacrolimus therapy . During 11 months the mean tacrolimus level was 8.2 ng/mL . The patient was hospitalized because of an episode of Shigella infection and a threefold increase in tacrolimus level was measured . Despite a reduction of tacrolimus dose, the trough tacrolimus levels were in the range of 16.5 to 22.0 ng/mL during the subsequent 2 weeks . On resolution of the diarrhea, tacrolimus levels returned to those observed before the Shigella infection . It is suggested that the marked increase in tacrolimus levels observed in this patient is a direct result of the damage produced to the gastrointestinal mucosa by the Shigella infection.

Zhonghua Nei Ke Za Zhi, 1999 Aug, 38(8), 550 - 3
{A study on the mechanism of the resistance of Shigellae to fluoroquinolones}; Ding J et al.; OBJECTIVE: To study the mechanism of the resistance of Shigellae to fluoroquinolones . METHODS: A total of 157 clinical isolates were collected . Antibiotic susceptibility testing, reserpine reverse reaction and plasmid conjugation experiment were performed . Accumulation of norfloxacin by shigellae was determined . The N-terminal coding region of gyrA gene was amplified by polymerase chain reaction (PCR), cloned and sequenced in eight fluoroquinolone-resistant isolates and one fluoroquinolone-sensitive isolate as well as in Shigella 51573 (the standard strain) . RESULTS: The positive rate of norfloxacin-resistant isolates was 51.2% in the R plasmid conjugation experiment . R plasmid could not mediate resistance to fluoroquinolones . Reserpine could not decrease the minimum inhibition concentration of fluoroquinolones to Shigellae . Norfloxacin uptake by fluoroquinolone-resistant isolates was the same as that by the sensitive one . DNA sequence analysis of gyrA gene from fluoroquinolone-resistant isolates revealed five point mutations that resulted in amino acid change: Gly-81-->Ser, Ser-83-->Leu, Asp-87-->Asn, Asp-87-->Gly, Met-92-->Lys . CONCLUSION: The mutations of gyrA gene were implicated in the resistance of Shigellae to fluoroquinolones.

J Biol Chem, 2002 Apr 5, 277(14), 11653 - 63 Epub 2002 Jan 16.
Core oligosaccharides of Plesiomonas shigelloides O54:H2 (strain CNCTC 113/92): structural and serological analysis of the lipopolysaccharide core region, the O-antigen biological repeating unit, and the linkage between them; Niedziela T et al.; The structure of the core oligosaccharide moiety of the lipopolysaccharide (LPS) of Plesiomonas shigelloides O54 (strain CNCTC 113/92) has been investigated by (1)H and (13)C NMR, fast atom bombardment mass spectrometry (MS)/MS, matrix-assisted laser-desorption/ionization time-of-flight MS, monosaccharide and methylation analysis, and immunological methods . It was concluded that the main core oligosaccharide of this strain is composed of a decasaccharide with the following structure: (see text) in which l-alpha-D-Hepp is l-glycero-alpha-D-manno-heptopyranose . The nonasaccharide variant of the core oligosaccharide ( approximately 10%), devoid of beta-D-Glcp substituting the alpha-D-GlcpN at C-6, was also identified . The core oligosaccharide substituted at C-4 of the outer core beta-D-Glcp residue with the single O-polysaccharide repeating unit was also isolated yielding a hexadecasaccharide structure . The determination of the monosaccharides involved in the linkage between the O-specific polysaccharide part and the core, as well as the presence of -->3)-D-beta-D-Hepp-(1--> instead of -->3,4)-D-beta-D-Hepp-(1--> in the repeating unit, revealed the structure of the biological repeating unit of the O-antigen . The core oligosaccharides are not substituted by phosphate residues and represent novel core type of bacterial LPS that is characteristic for the Plesiomonas shigelloides serotype O54 . Serological screening of 69 different O-serotypes of P . shigelloides suggests that epitopes similar to the core oligosaccharide of serotype O54 (strain CNCTC 113/92) might also be present in the core region of the serotypes O24 (strain CNCTC 92/89), O37 (strain CNCTC 39/89) and O96 (strain CNCTC 5133) LPS.

Pediatr Nephrol, 2001 Dec, 16(12), 1142 - 5
Post-dysenteric hemolytic uremic syndrome in Bulawayo, Zimbabwe; Oneko M et al.; An outbreak of dysentery in Zimbabwe was associated with a high mortality, especially in children who developed hemolytic uremic syndrome (HUS) . To examine the causes of high mortality from HUS and to suggest measures that could reduce the case fatality rate, clinical and laboratory features of 91 children with dysentery were reviewed . Of these, 14 developed HUS; their findings were compared with age-matched controls with dysentery only . Persistent alteration of consciousness after rehydration, pallor, and oliguria were early clinical indicators of HUS . Leukocytosis and leukemoid reaction, microhematuria, and non-resolving hyponatremia distinguished children with HUS from those with dysentery . While Shigella dysenteriae type I was responsible for the dysentery outbreak in the community, most stool cultures of children with HUS were negative . Mortality from HUS was high . Late recognition of HUS and a lack of peritoneal dialysis could have contributed to the fatal outcome in some cases . Early recognition of HUS through close observation of children with dysentery and appropriate laboratory investigations with referral to a hospital, where peritoneal dialysis is available, should improve the outcome.

Adv Exp Med Biol, 2001, 501, 457 - 67
Protective role of human lactoferrin against invasion of Shigella flexneri M90T; Gomez HF et al.; Lactoferrin is an iron-binding protein found in human mucosal secretions such as milk . A variety of functions have been ascribed to this protein, it appears to contribute to antimicrobial host defense . Still its overall physiological role remains to be defined . We sought to study the role of recombinant human lactoferrin (rhLf) in Shigella infection . Invasion of epithelial cells is essential to the development of bacillary dysentery . Shigella flexneri 5 M90T, a virulent strain, was evaluated in the classic HeLa cell invasion model, in immunoblots, and by transmission electron microscopy, immunofluorescence, and deconvolved microscopy Bacteria not exposed to rhLf were used as controls . We found that rhLf decreased significantly the invasiveness of S . flexneri 5 M90T in a HeLa cell model . The immunoblot data showed that invasion plasmid antigen B (IpaB) was released from the bacteria during incubation with rhLf . Lactoferrin treatment did not directly dissociate the complex of IpaB and IpaC (IpaBC) once the complex had been formed . Furthermore, ferric iron had no effect on release of IpaB . Electron microscopy of rhLf-treated bacteria suggested a reduction in vacuolization of the HeLa cell cytoplasm and decreased number of bacteria within HeLa cells . At 40,000 x magnification the few rhLf-treated Shigella that invaded exhibited a dense ring completely surrounding them . Immunofluorescence and deconvolved microscopy suggested that rhLf-treated bacteria were completely surrounded by a thick layer of actin . The fact that two cell surface functions (invasion and actin-mediated movement) were deranged suggests that rhLf disrupts the integrity of the bacterial outer membrane in which virulence proteins are anchored . The mechanism by which rhLf impairs Shigella invasiveness may be relevant to other enteropathogens that share similar virulence strategies.

MMWR Morb Mortal Wkly Rep, 2001 Sep 21, 50(37), 797 - 800
Shigellosis outbreak associated with an unchlorinated fill-and-drain wading pool--Iowa, 2001; Performance decrement after combined exposure to ionizing radiation and Shigella sonnei; Armed Forces Radiobiology Research Institute, 8901 Wisconsin Avenue, Bethesda, MD 20889-5603, USAIonizing radiation could increase morbidity from common bacterial infections in military personnel on the modern battlefield . The combined effects of a sublethal dose of ionizing radiation and the bacterial diarrheal agent Shigella sonnei on body weight and forelimb grip strength in mice were assessed over a 30-day period . Individually housed B6D2F1 female mice were divided into four groups: control, sham irradiation + gavage with saline vehicle; 3 Gy 60Co gamma radiation at 0.4 Gy/min radiation + saline gavage; sham irradiation + 1.3 x 10(8) colony-forming units (CFUs) S . sonnei via gavage, administered 4 days postirradiation; and the combination of 3 Gy 60Co gamma radiation + 1.3 x 10(8) CFUs S . sonnei . Behavioral tests were conducted 3 days preirradiation and on days 9, 14, and 22 postirradiation . Body weight was significantly reduced in the radiation + Shigella group on days 5 to 10 postirradiation . Forelimb grip strength was reduced for mice in the radiation + Shigella group on days 9 and 14 postirradiation . These data demonstrate that an exposure to gamma radiation in combination with the bacterial agent S . sonnei can lead to a synergistic loss of body weight and degradation in performance.

Kansenshogaku Zasshi, 2001 Nov, 75(11), 923 - 30
{Increasing incidence and the mechanism of resistance of nalidixic acid resistant Shigella sonnei}; Uchimura M et al.; One hundred and fourteen Shigella sonnei strains obtained in 1991 to 2000 were tested for their susceptibilities to 12 antimicrobial agents . Nalidixic acid (NA) resistance was found in 2 of 15 strains (13.3%) in 1993, 2 of 8 strains (25%) in 1996, one of 5 strains (20%) in 1998, 7 of 21 strains (33.3%) in 1999 and 6 of 12 strains (50%) in 2000 . The incidence of resistance to NA in S . sonnei strains increased significantly during this period . Among those 19 NA resistant strains, 11 strains were derived from patients with traveler's diarrhea and 8 strains were derived from patients who had not traveled abroad before the infection, namely domestic patients . PFGE analysis with Xba I revealed that all strains tested differentiated into two major clonal clusters, one cluster consisted of strains derived from patients who had traveled to India after 1993, and another cluster included strains derived from domestic patients . Mechanism of NA resistance was examined by sequencing the quinolone resistance-determining region (QRDR) of gyrA gene . Among 19 NA resistant strains tested, 11 strains presented a change at Ser-83 to Leu and 7 strains presented a change at Asp-87 to Try (5 strains) or Asn (2 strains), whereas 3 NA sensitive strains had no change in the region . These findings indicated that this mutation in gyrA plays an important role in acquisition of Nalidixic-acid resistance in clinical isolates of S . sonnei.

J Health Popul Nutr, 2001 Sep, 19(3), 183 - 90
Epidemiology of shigellosis in Lagos, Nigeria: trends in antimicrobial resistance; Iwalokun BA et al.; Antimicrobial susceptibility of Shigella spp . and Escherichia coli, isolated from diarrhoeal patients in Lagos, was studied from March 1999 to February 2000 . Four hundred fifty-nine isolates were identified as shigellae (62) and E . coli (397) . Shigella flexneri, S . dysenteriae, S . boydii, and S . sonnei accounted, respectively, for 51.6%, 17.7%, 17.7%, and 13% of the total number of shigellae isolated . Eleven cases of shigellosis occurred in the age group of 0-9 years, 22 cases in the age group of 10-19 years, and 29 cases in the age group of > or = 20 years . Of the 397 E . coli isolates, 11 were enteropathogenic E . coli (EPEC), and 7 of these strains were isolated with shigellae from stools of patients aged 0-9 year(s) (71.4%) and 10-19 years (28.6%) . Over 70% of the Shigella isolates were resistant to two or more drugs, including ampicillin and tetracycline . Twenty-one distinct multidrug resistance patterns were observed in these isolates . During 1990-2000, resistance to ampicillin increased from 70% to 90%, co-trimoxazole from 77% to 85%, chloramphenicol from 71% to 77%, streptomycin from 71% to 79%, and nalidixic acid from 0% to 11.3% . Resistance to tetracycline decreased from 89% to 79% but with MIC50 and MIC90 values outside the susceptible range . While resistance to ciprofloxacin and ofloxacin remained nil with MIC50 and MIC90 values of 0.008 and 0.0016 microgram/mL respectively . The results of this study revealed the endemicity of shigellosis with S . flexneri as the predominant serogroup in Lagos . Children and young adults were at a higher risk of severe shigellosis . The results also suggest that ampicillin, tetracycline, co-trimoxazole, and streptomycin should not be used as the first-line drugs in the treatment of shigellosis . Nalidixic acid should still be selectively used for treatment, while ciprofloxacin and ofloxacin can be ideal alternatives.

J Health Popul Nutr, 2001 Sep, 19(3), 177 - 82
Survival of Shigella dysenteriae type 1 on fomites; Islam MS et al.; Studies have shown that various objects, such as utensils, toys, and clothes, can serve as vehicles for transmission of Shigella spp . Shigellae can become viable but non-culturable (VBNC) when exposed to various environmental conditions as shown in earlier studies . The present study was carried out to detect VBNC Shigella dysenteriae type 1 on various fomites by direct viable counting, polymerase chain reaction (PCR), and fluorescent antibody methods . S . dysenteriae type 1 was inoculated onto cloth, wood, plastic, aluminum, and glass objects . Results showed that 1.5-4.0 hours after inoculation, S . dysenteriae type 1 became non-culturable, and after five days, non-culturable but viable S . dysenteriae type 1 could be detected by both PCR and fluorescent antibody techniques . Fomites can be considered an important potential route of transmission of VBNC S . dysenteriae type 1 and a significant factor in the epidemiology of shigellosis.

J Endotoxin Res, 2001, 7(6), 442 - 6
Blockade of CD14 aggravates experimental shigellosis; Wenneras C et al.; Shigella infections lead to severe inflammation associated with destruction of colonic mucosa . We assessed the effect of in vivo blockade of CD14 on the outcome of experimental Shigella infection in rabbits . A total of 17 rabbits were divided into two groups: 8 received a single i.v . dose of anti-rabbit CD14 monoclonal antibody prior to infection with an invasive Shigella flexneri strain; the remainder served as controls . The anti-CD14-treated rabbits exhibited more severe tissue destruction and a 50-fold increase in bacterial invasion of the intestinal mucosa when compared to controls . Similar numbers of polymorphonuclear leukocytes were recruited to the intestinal mucosa in both groups despite the massive bacterial invasion seen in the CD14-blocked group . No statistically significant differences were seen in levels of IL-1beta nor in the ratio of IL-1RA/IL-1beta for either group . In contrast, higher quantities of TNF-alpha were observed in the CD14-blocked group . To conclude, anti-CD14 treatment had a detrimental effect on the capacity of Shigella-infected animals to clear the infection.

J Bacteriol, 2002 Jan, 184(2), 605 - 9
High frequency of mutator strains among human uropathogenic Escherichia coli isolates; Denamur E et al.; By using a panel of 603 commensal and pathogenic Escherichia coli and Shigella isolates, we showed that mutation rates of strains vary considerably among different ecotypes . Uropathogenic strains had the highest frequency of mutators, while strains from patients with bacteremia had the lowest mutation rates . No correlation between the mutation rates and antibiotic resistance was observed among the studied strains.

J Bacteriol, 2002 Jan, 184(2), 531 - 9
In vivo DNA-binding and oligomerization properties of the Shigella flexneri AraC-like transcriptional regulator VirF as identified by random and site-specific mutagenesis; Porter ME et al.; In Shigella flexneri expression of the plasmid-encoded virulence genes is regulated via a complex mechanism involving both environmental signals and specific transactivators . The primary regulator protein, VirF, is a member of the AraC family of transcription factors and shares with other AraC-like proteins a conserved carboxy-terminal domain thought to be important for DNA binding . Random and site-directed mutagenesis of the virF gene encoding VirF yielded a number of mutations along the length of the protein which severely affected the ability of VirF to activate gene expression . The mutant proteins were shown to be affected in their ability to activate the virulence genes virB and icsA, both known to be regulated directly by VirF, as well as the virB-dependent virulence gene mxiC . Mutating key residues predicted to be important for DNA recognition had a significant negative effect, thereby suggesting that VirF interacts with its target sequence via two helix-turn-helix motifs . Two mutants that were dominant negative when coexpressed with the wild-type VirF protein were also isolated, indicating a role for protein-protein oligomerization in normal VirF function.

FEMS Immunol Med Microbiol, 2001 Dec, 32(1), 43 - 6
Enhanced anti-Shigella activity of erythromycin supplemented with sulfadiazine; Honma Y et al.; Sulfadiazine enhanced the anti-Shigella activity of erythromycin . Erythromycin passes through the type III secretion apparatus and suppresses the growth of invasive Shigella organisms . Sulfadiazine enhanced this effect at the concentration under minimum inhibitory concentration and it came from not only the folate-inhibiting activity but also from a new function . It has proved that sulfadiazine stimulated type III secretion in Shigella as determined from the secretion of the pathogenic protein IpaB . As Congo red induced secretion of Ipa proteins and uptake of erythromycin through the type III secretion gate, sulfadiazine which is similar to Congo red in chemical structure may induce the uptake in the same way.

Glycobiology, 2001 Nov, 11(11), 945 - 55
Conformation of the O-specific polysaccharide of Shigella dysenteriae type 1: molecular modeling shows a helical structure with efficient exposure of the antigenic determinant alpha-L-Rhap-(1-->2)-alpha-D-Galp; Nyholm PG et al.; The O-specific polysaccharide of Shigella dysenteriae type 1, which has the repeating tetrasaccharide unit -->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-D-Galp-(1-->3)-alpha-D-GlcNAcp-(1--> (A-B-C-D), is a major virulence factor, and it is believed that antibodies against this polysaccharide confer protection to the host . The conformational properties of fragments of this O-antigen were explored using systematic search with a modified HSEA method (GLYCAN) and with molecular mechanics MM3(96) . The results show that the alpha-D-Gal-(1-->3)-alpha-D-GlcNAc linkage adopts two favored conformations, phi/psi approximately equal to -40 degrees /-30 degrees (I) and approximately 15 degrees /30 degrees (II), whereas the other glycosidic linkages only have a single favored phi/psi conformational range . MM3 indicates that the trisaccharide B-C-D and tetrasaccharides containing the B-C-D moiety exist as two different conformers, distinguished by the conformations I and II of the C-D linkage . For the pentasaccharide A-B-C-D-A' and longer fragments, the calculations show preference for the C-D conformation II . These results can explain previously reported nuclear magnetic resonance data . The pentasaccharide in its favored conformation II is sharply bent, with the galactose residue exposed at the vertex . This hairpin conformation of the pentasaccharide was successfully docked with the binding site of a monoclonal IgM antibody (E3707 E9) that had been homology modeled from known crystal structures . For fragments made of repetitive tetrasaccharide units, the hairpin conformation leads to a left-handed helical structure with the galactose residues protruding radially at the helix surface . This arrangement results in a pronounced exposure of the galactose and also the adjacent rhamnose in each repeating unit, which is consistent with the known role of the as alpha-L-Rhap-(1-->2)-alpha-D-Galp moiety as a major antigenic epitope of this O-specific polysaccharide.

Pediatr Infect Dis J, 2001 Dec, 20(12), 1178 - 9
Plesiomonas shigelloides sepsis and splenic abscess in an adolescent with sickle-cell disease; Ampofo K et al.; Plesiomonas shigelloides is a rare cause of self-limiting gastroenteritis . We report a case of extraintestinal P . shigelloides infection in an adolescent with sickle-cell disease who presented with bacteremia complicated by a splenic abscess . Despite the high mortality rate reported in extraintestinal P . shigelloides infection, the patient survived after drainage of the abscess and treatment with antibiotics.

Mol Microbiol, 2001 Nov, 42(4), 1133 - 45
Characterization of the interaction partners of secreted proteins and chaperones of Shigella flexneri; Page AL et al.; The type III secretion (TTS) system of Gram-negative pathogenic bacteria is composed of proteins that assemble into the TTS machinery, proteins that are secreted by this machinery and specific chaperones that are required for storage and sometimes secretion of these proteins . Many sequential protein interactions are involved in the TTS pathway to deliver effector proteins to host cells . We used the yeast two-hybrid system to investigate the interaction partners of the Shigella flexneri effectors and chaperones . Libraries of preys containing random fusions with fragments of the TTS proteins were screened using effectors and chaperones as baits . Interactions between the effectors IpaB and IpaC and their chaperone IpgC were detected by this method, and interaction domains were identified . Using a His-tagged IpgC protein to co-purify truncated IpaB and IpaC proteins, we showed that the chaperone-binding domain was unique and located in the N-terminus of these proteins . This domain was not required for the secretion of recombinant proteins but was involved in the stability of IpaC and instability of IpaB . Homotypic interactions were identified with the baits IpaA, IpaB and IpaC . Interactions between effectors and components of the TTS machinery were also selected that might give insights into regulation of the TTS process.

Microbiol Mol Biol Rev, 2001 Dec, 65(4), 595 - 626, table of contents
Actin-based motility of intracellular microbial pathogens; Goldberg MB; A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells . These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells . Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface . The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells . Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility . Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step . In addition, the microbial molecules involved are each distinctly different from the others . Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery . The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review.

J Bacteriol, 2001 Dec, 183(24), 6991 - 8
MxiM and MxiJ, base elements of the Mxi-Spa type III secretion system of Shigella, interact with and stabilize the MxiD secretin in the cell envelope; Schuch R et al.; The type III secretion pathway is broadly distributed across many parasitic bacterial genera and serves as a mechanism for delivering effector proteins to eukaryotic cell surface and cytosolic targets . While the effectors, as well as the host responses elicited, differ among type III systems, they all utilize a conserved set of 9 to 11 proteins that together form a bacterial envelope-associated secretory organelle or needle complex . The general structure of the needle complex consists of a transenvelope base containing at least three ring-forming proteins (MxiD, MxiJ, and MxiG in Shigella) that is connected to a hollow needle-like extension that projects away from the cell surface . Several studies have shown that the initial steps in needle complex assembly require interactions among the base proteins, although specific details of this process remain unknown . Here we identify a role for another base element in Shigella, MxiM, in interactions with the major outer-membrane-associated ring-forming protein, MxiD . MxiM affects several features of MxiD, including its stability, envelope association, and assembly into homomultimeric structures . Interestingly, many of the effects were also elicited by the inner-membrane-associated base element, MxiJ . We confirmed that MxiM-MxiD and MxiJ-MxiD interactions occur in vivo in the cell envelope, and we present evidence that together these base elements can form a transmembrane structure which is likely an important intermediary in the process of needle complex assembly.

Immunol Lett, 2002 Jan 1, 80(1), 15 - 9
The immunosuppressive activity of chemically modified lipopolysaccharide of Shigella sonnei; Vikstrom EV; In the present investigations we aimed to study the effect of Shigella sonnei lipopolysaccharide (LPS) on delayed type hypersensitivity (DTH) to non-bacterial antigen in CBA mice . These experiments showed that intraperitoneal injection of phenol-water extracted LPS and avirulent S . sonnei did not affect the level of DTH . However, an injection of avirulent bacteria and LPS treated with 2-mercaptoethanol reduced significantly the levels of DTH . Gel filtration of redox-reactivated LPS through Sephadex G-200 shows that LPS contains three immunosuppressive components: approximately 800 kDa and higher, 150-200 and 50-70 kDa . These components differed by their specificity and heat-sensitivity.

Infect Immun, 2001 Dec, 69(12), 7588 - 95
Characterization of a Shiga toxin-encoding temperate bacteriophage of Shigella sonnei; Strauch E et al.; A Shiga toxin (Stx)-encoding temperate bacteriophage of Shigella sonnei strain CB7888 was investigated for its morphology, DNA similarity, host range, and lysogenization in Shigella and Escherichia coli strains . Phage 7888 formed plaques on a broad spectrum of Shigella strains belonging to different species and serotypes, including Stx-producing Shigella dysenteriae type 1 . With E . coli, only strains with rough lipopolysaccharide were sensitive to this phage . The phage integrated into the genome of nontoxigenic S . sonnei and laboratory E . coli K-12 strains, which became Stx positive upon lysogenization . Moreover, phage 7888 is capable of transducing chromosomal genes in E . coli K-12 . The relationships of phage 7888 with the E . coli Stx1-producing phage H-19B and the E . coli Stx2-producing phage 933W were investigated by DNA cross-hybridization of phage genomes and by nucleotide sequencing of an 8,053-bp DNA region of the phage 7888 genome flanking the stx genes . By these methods, a high similarity was found between phages 7888 and 933W . Much less similarity was found between phages H-19B and 7888 . As in the other Stx phages, a regulatory region involved in Q-dependent expression is found upstream of stxA and stxB (stx gene) in phage 7888 . The morphology of phage 7888 was similar to that of phage 933W, which shows a hexagonal head and a short tail . Our findings demonstrate that stx genes are naturally transferable and are expressed in strains of S . sonnei, which points to the continuous evolution of human-pathogenic Shigella by horizontal gene transfer.

Infect Immun, 2001 Dec, 69(12), 7471 - 80
Pathoadaptive mutations that enhance virulence: genetic organization of the cadA regions of Shigella spp; Day WA Jr et al.; Pathoadaptive mutations improve the fitness of pathogenic species by modification of traits that interfere with factors (virulence and ancestral) required for survival in host tissues . A demonstrated pathoadaptive mutation is the loss of lysine decarboxylase (LDC) expression in Shigella species that have evolved from LDC-expressing Escherichia coli . Previous studies demonstrated that the product of LDC activity, cadaverine, blocks the action of Shigella enterotoxins and that the gene encoding LDC, cadA, was abolished by large chromosomal deletions in each Shigella species . To better understand the nature and evolution of these pathoadaptive mutations, remnants of the cad region were sequenced from the four Shigella species . These analyses reveal novel gene arrangements in this region of the pathogens' chromosomes . Insertion sequences, a phage genome, and/or loci from different positions on the ancestral E . coli chromosome displaced the cadA locus to form distinct genetic linkages that are unique to each Shigella species . Hybridization studies, using an E . coli K-12 microarray, indicated that the genes displaced to form the novel linkages still remain in the Shigella genomes . None of these novel gene arrangements were observed in representatives of all E . coli phylogenies . Collectively, these observations indicate that inactivation of the cadA antivirulence gene occurred independently in each Shigella species . The convergent evolution of these pathoadaptive mutations demonstrates that, following evolution from commensal E . coli, strong pressures in host tissues selected Shigella clones with increased fitness and virulence through the loss of an ancestral trait (LDC) . These observations strongly support the role of pathoadaptive mutation as an important pathway in the evolution of pathogenic organisms.

Mol Microbiol, 2001 Oct, 42(2), 439 - 52
Involvement of FIS in the H-NS-mediated regulation of virF gene of Shigella and enteroinvasive Escherichia coli; Falconi M et al.; The mechanism of pathogenicity in Shigella and enteroinvasive Escherichia coli (EIEC) requires the co-ordinated expression of several genes located on both the virulence plasmid and the chromosome . We found that cells lacking a functional FIS protein (factor for inversion stimulation) are partially impaired in expressing the virulence genes and that full expression is totally restored when Shigella wild-type fis gene is offered in trans . We also identified virF, among the virulence genes, as a target of FIS-mediated activation and showed that FIS binds to four specific sites in the promoter region of virF . Previous studies have demonstrated that the expression of VirF, the first positive activator of a multistep regulatory cascade, is subject to temperature-dependent regulation by H-NS, one of the main nucleoid-associated proteins . We now demonstrate that two of the four FIS sites overlap one of the two H-NS sites responsible for thermoregulation (H-NS site I) . FIS was found to exercise a direct positive transcriptional control at permissive temperature (37 degrees C), when H-NS fails to repress virF, as well as an indirect effect by partially counteracting H-NS inhibition at the transition temperature (32 degrees C) . Our data indicate that FIS may be relevant for the rapid increase in virF expression after penetration of bacteria into the host.

MMWR Morb Mortal Wkly Rep, 2001 Oct 26, 50(42), 922 - 6
Shigella sonnei outbreak among men who have sex with men--San Francisco, California, 2000-2001; Controlled expression in Klebsiella pneumoniae and Shigella flexneri using a bacteriophage P1-derived C1-regulated promoter system; Department of Microbiology and Immunology, Medical University of South Carolina, 173 Ashley Ave., Charleston, SC 29403, USA . schofida@musc.edu

The utility of promoters regulated by the bacteriophage P1 temperature-sensitive C1 repressor was examined in Shigella flexneri and Klebsiella pneumoniae . Promoters carrying C1 operator sites driving LacZ expression had induction/repression ratios of up to 240-fold in S . flexneri and up to 50-fold in K . pneumoniae . The promoters exhibited remarkably low basal expression, demonstrated modulation by temperature, and showed rapid induction . This system will provide a new opportunity for controlled gene expression in enteric gram-negative bacteria.

Epidemiol Infect, 2001 Oct, 127(2), 375 - 9
Frequency of failure to isolate Shigella spp . by the direct plating technique and improvement of isolation by enrichment in selenite broth; Miyagi K et al.; In order to clarify the failure to isolate Shigella spp . by direct plating, we compared frequencies of Shigella spp . isolation by direct plating and by plating after enrichment in selenite broth . A total 67 strains were isolated in this study . The strains of 38 (56.7%) were isolated only by direct plating, and 25 (37.3%) strains were isolated by both direct plating and after enrichment . Four strains (6.0%) were isolated after enrichment but not by direct plating . Since 6% of isolated Shigella spp . were not isolated by direct plating, we recommend that direct plating and additional isolations from selenite broth should be performed . The significance concerning reduction of concentration of sodium selenite in enrichment broth is discussed.

J Virol, 2001 Dec, 75(23), 11651 - 63
Vaccinia virus intracellular movement is associated with microtubules and independent of actin tails; Ward BM et al.; Two mechanisms have been proposed for the intracellular movement of enveloped vaccinia virus virions: rapid actin polymerization and microtubule association . The first mechanism is used by the intracellular pathogens Listeria and Shigella, and the second is used by cellular vesicles transiting from the Golgi network to the plasma membrane . To distinguish between these models, two recombinant vaccinia viruses that express the B5R membrane protein fused to enhanced green fluorescent protein (GFP) were constructed . One had Tyr(112) and Tyr(132) of the A36R membrane protein, which are required for phosphorylation and the nucleation of actin tails, conservatively changed to Phe residues; the other had the A36R open reading frame deleted . Although the Tyr mutant was impaired in Tyr phosphorylation and actin tail formation, digital video and time-lapse confocal microscopy demonstrated that virion movement from the juxtanuclear region to the periphery was saltatory with maximal speeds of >2 microm/s and was inhibited by the microtubule-depolymerizing drug nocodazole . Moreover, this actin tail-independent movement was indistinguishable from that of a control virus with an unmutated A36R gene and closely resembled the movement of vesicles on microtubules . However, in the absence of actin tails, the Tyr mutant did not induce the formation of motile, virus-tipped microvilli and had a reduced ability to spread from cell to cell . The deletion mutant was more severely impaired, suggesting that the A36R protein has additional roles . Optical sections of unpermeabilized, B5R antibody-stained cells that expressed GFP-actin and were infected with wild-type vaccinia virus revealed that all actin tails were associated with virions on the cell surface . We concluded that the intracellular movement of intracellular enveloped virions occurs on microtubules and that the motile actin tails enhance extracellular virus spread to neighboring cells.

Res Microbiol, 2001 Oct, 152(8), 687 - 95
Shiga-toxin-converting bacteriophages; Schmidt H; Shiga toxins (Stx) comprise a family of potent cytotoxins that are involved in severe human disease . Stx are mainly produced by Escherichia coli isolated from human and nonhuman sources, and by Shigella dysenteriae type 1 . The genes encoding Stx are thought to be generally encoded in the genome of lambdoid prophages (Stx-converting bacteriophages; Stx phages) . They share a unique position in the late region of the phage genome downstream of the late promoter PR' . This location suggests that expression of stx is controlled by a Q-like antiterminator . Therefore, induction of Stx-converting prophages appears to trigger increased production of Stx . Following induction, Stx phages can be transduced in vivo and in vitro into other bacteria . Stx phages play an important role in the expression of Stx and in lateral gene transfer and are therefore a contribution to the emergence of new Stx-producing E . coli (STEC) variants.

FEMS Microbiol Lett, 2001 Oct 16, 204(1), 81 - 8
Inactivation of DsbA alters the behaviour of Shigella flexneri towards murine and human-derived macrophage-like cells; Yu J et al.; The mutants of Shigella flexneri, Sh4 (dsbA::kan) and Sh42 (dsbA33G), behave differently towards murine and human-derived macrophage-like cells in vitro . Sh4 was trapped in the phagocytic vacuoles of the murine J774 cells as evidenced by its colony forming units plus and minus chloroquine exposure in a gentamicin protection assay, and by light and transmission electron microscopy (TEM) . Sh42, similar to the wild-type M90TS, was able to escape from the vacuoles and kill host cells presumably by inducing apoptosis . In U937 cells, unlike M90TS that was free in the cytosol, both Sh4 and Sh42 grew poorly . TEM revealed that Sh4 and Sh42 were trapped within the U937 phagocytic vacuoles . Furthermore, the two mutants induced different patterns of interleukin-1beta and tumour necrosis factor-alpha expression, which might explain why they possess different immunogenic properties in vivo.

Int J Med Microbiol, 2001 Sep, 291(4), 287 - 98
Exploitation of host factors for efficient infection by Shigella; Adam T; Shigellosis is a worldwide endemic ulcerating disease of the large intestine caused by enteroinvasive bacteria . Shigella takes the route via M-cells and macrophages to access the basolateral pole of enterocytes . After invasion of and cell-to-cell spread within the epithelial cell layer, the bacterium multiplies within the cytoplasm of enterocytes . Induced by a limited number of bacterial effector proteins, Shigella makes use of established signaling pathways of the host cell to achieve internalization, transcytosis, apoptosis or cell-to-cell spread . This review addresses the host factors required for efficient infection focusing on Shigella-induced cytoskeletal rearrangements and associated signaling.

Biochem Biophys Res Commun, 2001 Nov 2, 288(3), 676 - 84
Gene cloning and characterization of alanine racemases from Shigella dysenteriae, Shigella boydii, Shigella flexneri, and Shigella sonnei; Yokoigawa K et al.; Alanine racemase genes (alr) from Shigella dysenteriae, Shigella boydii, Shigella flexneri, and Shigella sonnei were cloned and expressed in Escherichia coli JM109 . All genes encoded a polypeptide of 359 amino acids, and showed more than 99% sequence identities with each other . In particular, the S . dysenteriae alr was identical with the S . flexneri alr . Differences in the amino acid sequences between the four Shigella enzymes were only two residues: Gly138 in S . dysenteriae and S . flexneri (Glu138 in the other) and Ile225 in S . sonnei (Thr225 in the other) . The S . boydii enzyme was identical with the E . coli K12 alr enzyme . Each Shigella alr enzyme purified to homogeneity has an apparent molecular mass about 43,000 by SDS-gel electrophoresis, and about 46,000 by gel filtration . However, all enzymes showed an apparent molecular mass about 60,000 by gel filtration in the presence of a substrate, 0.1 M l-alanine . These results suggest that the Shigella alr enzymes having an ordinary monomeric structure interact with other monomer in the presence of the substrate . The enzymes were almost identical in the enzymological properties, and showed lower catalytic activities (about 210 units/mg) than those of homodimeric alanine racemases reported .

J Org Chem, 1998 Aug 21, 63(17), 5983 - 5999
Synthesis of Glycoconjugate Vaccines against Shigella dysenteriae Type 1; Pozsgay V; Syntheses of a hexadecasaccharide and smaller fragments corresponding to one-four repeating units of the O-specific polysaccharide of Shigella dysenteriae type 1 are reported in a reactive aglycon-linked from . Two tetrasaccharide donor/acceptor repeating units were assembled from monosaccharide precursors in a stepwise fashion and used in a linear, iterative manner to construct the higher-membered saccharides using Schmidt's glycosylation technique that proved superior to others tested . Single-point attachment of the saccharides to human serum albumin, using a secondary heterobifunctional spacer, afforded a range of glycoconjugates for a detailed evaluation of their immunological characteristics.

Infect Immun, 2001 Nov, 69(11), 6923 - 30
Sequence analysis of four Shigella boydii O-antigen loci: implication for Escherichia coli and Shigella relationships; Wang L et al.; Shigella strains are in reality clones of Escherichia coli and are believed to have emerged relatively recently (G . M . Pupo, R . Lan, and P . R . Reeves, Proc . Natl . Acad . Sci . USA 97:10567-10572, 2000) . There are 33 O-antigen forms in these Shigella clones, of which 12 are identical to O antigens of other E . coli strains . We sequenced O-antigen gene clusters from Shigella boydii serotypes 4, 5, 6, and 9 and also studied the O53- and O79-antigen gene clusters of E . coli, encoding O antigens identical to those of S . boydii serotype 4 and S . boydii serotype 5, respectively . In both cases the S . boydii and E . coli O-antigen gene clusters have the same genes and organization . The clusters of both S . boydii 6 and S . boydii 9 O antigens have atypical features, with a functional insertion sequence and a wzx gene located in the orientation opposite to that of all other genes in S . boydii serotype 9 and an rmlC gene located away from other rml genes in S . boydii serotype 6 . Sequences of O-antigen gene clusters from another three Shigella clones have been published, and two of them also have abnormal structures, with either the entire cluster or one gene being located on a plasmid in Shigella sonnei or Shigella dysenteriae, respectively . It appears that a high proportion of clusters coding for O antigens specific to Shigella clones have atypical features, perhaps indicating recent formation of these gene clusters.

Toxicon, 2001 Nov, 39(11), 1629 - 35
Shiga toxins; Sandvig K; Shiga toxin and Shiga-like toxins belong to the group of protein toxins which have a moiety that binds to the cell surface and another enzymatically active moiety that after entry into the cytosol inhibits protein synthesis enzymatically . The toxins can also cause apoptosis by mechanisms that may be different from the effect on the protein synthesis machinery . Shigella dysenteriae, some strains of Escherichia coli as well as other bacteria can secrete such toxins which cause serious complications during infections . An increasing knowledge about the toxins and their interactions with cells is important both for treatment of disease, and for elucidation of pathways of intracellular transport.

Biochem Biophys Res Commun, 2001 Oct 19, 288(1), 91 - 100
Influence of the yihE gene of Shigella flexneri on global gene expression: on analysis using DNA arrays; Li MS et al.; Inactivation of dsbA (disulfide bond formation), either by an insertion (Sh4, dsbA::kan) or by alteration of the active site (Sh42, dsbA33G), renders Shigella flexneri avirulent . However, Sh4 and Sh42 behave differently in many ways in vitro and in vivo . A gene of unknown function, yihE, up-stream and cotranscribed with dsbA, is thought to differentiate Sh4 and Sh42 as the kan insertion may result in a truncated unstable yihE-dsbA mRNA in Sh4 . To gain insight into the function of yihE, DNA array hybridization was performed to study the genomic expression in Sh4, Sh42, and a newly constructed yihE mutant (Sh54) . Compared to the wild-type, M90TS, Sh4, and Sh54 demonstrated significantly changed transcription levels of about 100 genes, of which many involved in energy metabolism and stress response were down- and up-regulated, respectively . In contrast, Sh42 showed altered transcription levels of only 20 genes . The results argue that yihE is principally responsible for the changed genomic expression in Sh4 and Sh54 . Given the fact that the transcription of yihE-dsbA is regulated by the CpxRA two-component signal transduction system, yihE is probably involved in the extracytoplasmic stress response in a manor deserving further studies .

Gastroenterol Clin North Am, 2001 Sep, 30(3), 817 - 36
The role of antibiotics in the treatment of infectious diarrhea; Oldfield EC 3rd et al.; Infectious diarrhea is a significant cause of morbidity and mortality and a common complaint in clinical practice . Routine empirical use of antibiotics for infectious diarrhea should be avoided because of the self-limited nature of most cases, the cost of antibiotics, and the potential to worsen the already significant problem of antibiotic resistance of enteric pathogens . For patients with severe invasive or prolonged diarrhea or who are at high risk of complications, such as the elderly, diabetics, cirrhotics, and immunocompromised patients, empirical treatment with a quinolone antibiotic for 3 to 5 days can be considered . Antibiotic treatment can be highly effective for Shigella, ETEC, and V . cholerae infections, and metronidazole is indicated for C . difficile colitis . The impact of antibiotics for other specific pathogens is modest, and antibiotic therapy should be reserved for the same group of patients who would be considered for empirical treatment . The most significant problem in the antibiotic treatment of infectious diarrhea is the progressive increase in resistance among enteric pathogens; only the prudent use of antimicrobials in all areas of daily practice can limit or delay the impact of this serious problem.

Nat Cell Biol, 2001 Oct, 3(10), 897 - 904
N-WASP deficiency reveals distinct pathways for cell surface projections and microbial actin-based motility; Snapper SB et al.; The Wiskott-Aldrich syndrome protein (WASP) family of molecules integrates upstream signalling events with changes in the actin cytoskeleton . N-WASP has been implicated both in the formation of cell-surface projections (filopodia) required for cell movement and in the actin-based motility of intracellular pathogens . To examine N-WASP function we have used homologous recombination to inactivate the gene encoding murine N-WASP . Whereas N-WASP-deficient embryos survive beyond gastrulation and initiate organogenesis, they have marked developmental delay and die before embryonic day 12 . N-WASP is not required for the actin-based movement of the intracellular pathogen Listeria but is absolutely required for the motility of Shigella and vaccinia virus . Despite these distinct defects in bacterial and viral motility, N-WASP-deficient fibroblasts spread by using lamellipodia and can protrude filopodia . These results imply a crucial and non-redundant role for N-WASP in murine embryogenesis and in the actin-based motility of certain pathogens but not in the general formation of actin-containing structures.

Med Trop (Mars), 2001, 61(2), 143 - 7
{Causes of adult acute bacterial diarrhea in an internal medicine department in Libreville, Gabon}; Okome-Nkoumou M et al.; This retrospective study of patients treated between 1992 and 1996 was undertaken as a preliminary step to identifying the main bacterial causes of diarrheal disease in Libreville, Gabon . A total 371 files showing positive stool cultures were analyzed . From an epidemiological standpoint, data showed that the high risk population was young people of both sexes . The incidence of diarrhea was correlated with climatic conditions with an endemic-epidemic pattern characterized by peak activity during the rainy season . In the vast majority of cases, the underlying etiology was gastroenteritis due to invasive organisms . The most commonly identified agents were salmonellae (46.6%) and Shigellae (44.2%) . Treatment should focus on rehydration . Fluoro-quinolones were the most commonly indicated drugs for antimicrobial treatment but cotrimoxazole was often useful . In general, the prognosis of bacterial diarrhea is favorable provided that it is treated early and concurrent conditions are taken into account.

J Clin Microbiol, 2001 Oct, 39(10), 3757 - 9
Altering trends in the dominance of Shigella flexneri serotypes and emergence of serologically atypical S . flexneri strains in Dhaka, Bangladesh; Talukder KA et al.; Of 469 recently isolated Shigella flexneri strains, 452 agglutinated with Shigella flexneri-specific monoclonal antibodies . Of these, 396 could be assigned to 10 of the currently recognized 15 serotypes, with S . flexneri 2b dominating (23.2%) . Of the 56 untypeable strains which showed invasive properties, 17 were serologically atypical and the remaining 39 belonged to a new serotype.

J Clin Microbiol, 2001 Oct, 39(10), 3747 - 9
Identification of CTX-M-14 extended-spectrum beta-lactamase in clinical isolates of Shigella sonnei, Escherichia coli, and Klebsiella pneumoniae in Korea; Pai H et al.; CTX-M-14 beta-lactamase was identified in a stool isolate of Shigella sonnei and in blood isolates of Escherichia coli (one isolate) and Klebsiella pneumoniae (two isolates) from different parts of Korea . The amino acid sequence differed by one amino acid from CTX-M-9 (Ala-231--> Val) and was identical to that of beta-lactamases recently found in China and Japan.

Proc Natl Acad Sci U S A, 2001 Oct 9, 98(21), 12221 - 6 Epub 2001 Sep 25.
Microinjection and growth of bacteria in the cytosol of mammalian host cells; Goetz M et al.; Most facultative intracellular bacteria replicate in specialized phagosomes after being taken up by mammalian cells . Relatively few intracellular bacteria escape the phagosomal compartment with the help of cytolytic (pore-forming) proteins and replicate in the host cell cytosol . Without such toxins, intracellular bacteria cannot reach this cellular compartment . To circumvent the requirement of an "escape" step, we developed a procedure allowing the efficient direct injection of bacteria into the cytosol of mammalian cells . With this technique, we show that most bacteria, including extracellular bacteria and intracellular pathogens that normally reside in a vacuole, are unable to replicate in the cytosol of the mammalian cells . In contrast, microorganisms that replicate in the cytosol, such as Listeria monocytogenes, Shigella flexneri, and, to some extent, enteroinvasive Escherichia coli, are able to multiply in this cellular compartment after microinjection . Further L . monocytogenes with deletion in its PrfA-regulated hpt gene was found to be impaired in replication when injected into the cytosol . Complementation of the hpt mutation with a plasmid carrying the wild-type hpt gene restored the replication ability in the cytosol . These data indicate that cytosolic intracellular pathogens have evolved specific mechanisms to grow in this compartment of mammalian cells.

Biochemistry, 2001 Sep 25, 40(38), 11390 - 404
Listeria protein ActA mimics WASp family proteins: it activates filament barbed end branching by Arp2/3 complex; Boujemaa-Paterski R et al.; Actin-based propulsion of the bacteria Listeria and Shigella mimics the forward movement of the leading edge of motile cells . While Shigella harnesses the eukaryotic protein N-WASp to stimulate actin polymerization and filament branching through Arp2/3 complex, the Listeria surface protein ActA directly activates Arp2/3 complex by an unknown mechanism . Here we show that the N-terminal domain of ActA binds one actin monomer, in a profilin-like fashion, and Arp2/3 complex and mimics the C-terminal domain of WASp family proteins in catalyzing filament barbed end branching by Arp2/3 complex . No evidence is found for side branching of filaments by ActA-activated Arp2/3 complex . Mutations in the conserved acidic (41)DEWEEE(46) and basic (146)KKRRK(150) regions of ActA affect Arp2/3 binding but not G-actin binding . The motility properties of wild-type and mutated Listeria strains in living cells and in the medium reconstituted from pure proteins confirm the conclusions of biochemical experiments . Filament branching is followed by rapid debranching . Debranching is 3-4-fold faster when Arp2/3 is activated by ActA than by the C-terminal domain of N-WASp . VASP is required for efficient propulsion of ActA-coated beads in the reconstituted motility medium, but it does not affect the rates of barbed end branching/debranching by ActA-activated Arp2/3 nor the capping of filaments . VASP therefore affects another still unidentified biochemical reaction that plays an important role in actin-based movement.

J Virol, 2001 Oct, 75(20), 9665 - 70
Vaccination with a Shigella DNA vaccine vector induces antigen-specific CD8(+) T cells and antiviral protective immunity; Shata MT et al.; A prototype Shigella human immunodeficiency virus type 1 (HIV-1) gp120 DNA vaccine vector was constructed and evaluated for immunogenicity in a murine model . For comparative purposes, mice were also vaccinated with a vaccinia virus-env (vaccinia-env) vector or the gp120 DNA vaccine alone . Enumeration of the CD8(+)-T-cell responses to gp120 after vaccination using a gamma interferon enzyme-linked spot assay revealed that a single intranasal dose of the Shigella HIV-1 gp120 DNA vaccine vector elicited a CD8(+) T-cell response to gp120, the magnitude of which was comparable to the sizes of the analogous responses to gp120 that developed in mice vaccinated intraperitoneally with the vaccinia-env vector or intramuscularly with the gp120 DNA vaccine . In addition, a single dose of the Shigella gp120 DNA vaccine vector afforded significant protection against a vaccinia-env challenge . Moreover, the number of vaccinia-env PFU recovered in mice vaccinated intranasally with the Shigella vector was about fivefold less than the number recovered from mice vaccinated intramuscularly with the gp120 DNA vaccine . Since the Shigella vector did not express detectable levels of gp120, this report confirms that Shigella vectors are capable of delivering passenger DNA vaccines to host cells and inducing robust CD8(+) T-cell responses to antigens expressed by the DNA vaccines . Furthermore, to our knowledge, this is the first documentation of antiviral protective immunity following vaccination with a live Shigella DNA vaccine vector.

EMBO Rep, 2001 Sep, 2(9), 850 - 7
Actin pedestal formation by enteropathogenic Escherichia coli and intracellular motility of Shigella flexneri are abolished in N-WASP-defective cells; Lommel S et al.; In mammalian cells, actin dynamics is tightly controlled through small GTPases of the Rho family, WASP/Scar proteins and the Arp2/3 complex . We employed Cre/loxP-mediated gene targeting to disrupt the ubiquitously expressed N-WASP in the mouse germline, which led to embryonic lethality . To elucidate the role of N-WASP at the cellular level, we immortalized embryonic fibroblasts and selected various N-WASP-defective cell lines . These fibroblasts showed no apparent morphological alterations and were highly responsive to the induction of filopodia, but failed to support the motility of Shigella flexneri . In addition, enteropathogenic Escherichia coli were incapable of inducing the formation of actin pedestals in N-WASP-defective cells . Our results prove the essential role of this protein for actin cytoskeletal changes induced by these bacterial pathogens in vivo and in addition show for the first time that N-WASP is dispensable for filopodia formation.

FEMS Microbiol Lett, 2001 Sep 11, 203(1), 69 - 73
Modelling the vector pathway and infection of humans in an environmental outbreak of Escherichia coli O157; Strachan NJ et al.; Quantifying the transfer of Escherichia coli O157 from the environment to humans is essential for understanding outbreaks, establishing the infectious dose of the organism and proposing safeguards . We modelled the pathogen loading shed onto a field by sheep immediately prior to a scout camp where 18 scouts and two adults were infected with E . coli O157 . We estimated the dose ingested (4-24 organisms) which is in agreement with the low infective dose reported previously for this organism in food outbreaks . These data closely fit a surrogate Shigella dose-response model which can be used as a basis for risk assessment.

Infect Immun, 2001 Oct, 69(10), 6303 - 9
Molecular evolution of large virulence plasmid in Shigella clones and enteroinvasive Escherichia coli; Lan R et al.; Three genes, ipgD, mxiC, and mxiA, all in the invasion region of the Shigella virulence plasmid, were sequenced from strains representing a range of Shigella serotypes and from two enteroinvasive Escherichia coli (EIEC) isolates . The plasmids can be classified into two relatively homogeneous sequence forms which are quite distinct . pINV A plasmids are found in Shigella flexneri strains F6 and F6A, S . boydii strains B1, B4, B9, B10, B14, and B15, S . dysenteriae strains D3, D4, D6, D8, D9, D10, and D13, and the two EIEC strains (M519 and M520) . pINV B plasmids are present in S . flexneri strains F1A, F2A, F3A, F3C, F4A, and FY, two S . boydii strains (B11 and B12), and S . sonnei . The D1 pINV plasmid is a recombinant with ipgD gene more closely related to those of pINV A but with mxiA and mxiC genes more closely related to those of pINV B . The phylogenetic relationships of the plasmid and those of the chromosomal genes of Shigella strains are largely consistent . The cluster 1 and cluster 3 strains tested (G.M . Pupo, R . Lan, and P . R . Reeves, Proc . Natl . Acad . Sci . USA 97:10567-10572, 2000) have pINV A and pINV B plasmids, respectively . However, of the three cluster 2 strains (B9, B11, and B15), B9 and B15 have pINV A while B11 has a pINV B plasmid . Those Shigella (D8 and D10 and S . sonnei) and EIEC strains which do not group with the main body of Shigella strains based on chromosomal genes were found to have plasmids belonging to one or the other of the two types and must have acquired these by lateral transfer.

Infect Immun, 2001 Oct, 69(10), 6248 - 55
Release of Toll-like receptor-2-activating bacterial lipoproteins in Shigella flexneri culture supernatants; Aliprantis AO et al.; Shigella spp . cause dysentery, a severe form of bloody diarrhea . Apoptosis, or programmed cell death, is induced during Shigella infections and has been proposed to be a key event in the pathogenesis of dysentery . Here, we describe a novel cytotoxic activity in the sterile-culture supernatants of Shigella flexneri . An identical activity was identified in purified S . flexneri endotoxin, defined here as a mixture of lipopolysaccharide (LPS) and endotoxin-associated proteins (EP) . Separation of endotoxin into EP and LPS revealed the activity to partition exclusively to the EP fraction . Biochemical characterization of S . flexneri EP and culture supernatants, including enzymatic deactivation, reverse-phase high-pressure liquid chromatography analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and a Toll-like receptor-2 (TLR2) activation assay, indicates that the cytotoxic component is a mixture of bacterial lipoproteins (BLP) . We show that biologically active BLP are liberated into culture supernatants of actively growing S . flexneri . In addition, our data indicate that BLP, and not LPS, are the component of endotoxin of gram-negative organisms responsible for activating TLR2 . The activation of apoptosis by BLP shed from S . flexneri is discussed as a novel aspect of the interaction of bacteria with the host.

Infect Immun, 2001 Oct, 69(10), 6012 - 21
Ferric dicitrate transport system (Fec) of Shigella flexneri 2a YSH6000 is encoded on a novel pathogenicity island carrying multiple antibiotic resistance genes; Luck SN et al.; Iron uptake systems which are critical for bacterial survival and which may play important roles in bacterial virulence are often carried on mobile elements, such as plasmids and pathogenicity islands (PAIs) . In the present study, we identified and characterized a ferric dicitrate uptake system (Fec) in Shigella flexneri serotype 2a that is encoded by a novel PAI termed the Shigella resistance locus (SRL) PAI . The fec genes are transcribed in S . flexneri, and complementation of a fec deletion in Escherichia coli demonstrated that they are functional . However, insertional inactivation of fecI, leading to a loss in fec gene expression, did not impair the growth of the parent strain of S . flexneri in iron-limited culture media, suggesting that S . flexneri carries additional iron uptake systems capable of compensating for the loss of Fec-mediated iron uptake . DNA sequence analysis showed that the fec genes are linked to a cluster of multiple antibiotic resistance determinants, designated the SRL, on the chromosome of S . flexneri 2a . Both the SRL and fec loci are carried on the 66,257-bp SRL PAI, which has integrated into the serX tRNA gene and which carries at least 22 prophage-related open reading frames, including one for a P4-like integrase . This is the first example of a PAI that carries genes encoding antibiotic resistance and the first report of a ferric dicitrate uptake system in Shigella.

Trends Microbiol, 2001 Sep, 9(9), 419 - 24
When does a clone deserve a name? A perspective on bacterial species based on population genetics; Lan R et al.; Molecular population-genetic analysis has revealed that for several human diseases, including tuberculosis, plague and shigellosis, the generally accepted taxonomic status of the organisms involved does not fit the usually accepted genus or species criteria . This raises the question of what species concept to apply to bacteria . We suggest that the species definition in bacteria should be based on analysis of sequence variation in housekeeping genes, and also that the "clone" be given official status in bacterial nomenclature . This will allow demotion of the species or genus status of several traditionally recognized human pathogens, but retention of current names of anomalous species and genera as clone names.

Cell Microbiol, 2001 Sep, 3(9), 633 - 47
Actin-based motility is sufficient for bacterial membrane protrusion formation and host cell uptake; Monack DM et al.; Shigella flexneri replicates in the cytoplasm of host cells, where it nucleates host cell actin filaments at one pole of the bacterial cell to form a 'comet tail' that propels the bacterium through the host's cytoplasm . To determine whether the ability to move by actin-based motility is sufficient for subsequent formation of membrane-bound protrusions and intercellular spread, we conferred the ability to nucleate actin on a heterologous bacterium, Escherichia coli . Previous work has shown that IcsA (VirG), the molecule that is necessary and sufficient for actin nucleation and actin-based motility, is distributed in a unipolar fashion on the surface of S . flexneri . Maintenance of the unipolar distribution of IcsA depends on both the S . flexneri outer membrane protease IcsP (SopA) and the structure of the lipopolysaccharide (LPS) in the outer membrane . We co-expressed IcsA and IcsP in two strains of E . coli that differed in their LPS structures . The E . coli were engineered to invade host cells by expression of invasin from Yersinia pseudotuberculosis and to escape the phagosome by incubation in purified listeriolysin O (LLO) from Listeria monocytogenes . All E . coli strains expressing IcsA replicated in host cell cytoplasm and moved by actin-based motility . Actin-based motility alone was sufficient for the formation of membrane protrusions and uptake by recipient host cells . The presence of IcsP and an elaborate LPS structure combined to enhance the ability of E . coli to form protrusions at the same frequency as S . flexneri, quantitatively reconstituting this step in pathogen intercellular spread in a heterologous organism . The frequency of membrane protrusion formation across all strains tested correlates with the efficiency of unidirectional actin-based movement, but not with bacterial speed.

J Infect, 2001 May, 42(4), 227 - 34
Apoptotic cell death in the pathogenesis of infectious diseases; Dockrell DH; Apoptosis is a physiological process critical for tissue homeostasis . It is essential for the regulation of immune responses . A series of molecules transduce apoptoic signals and induce the characteristic morphological appearances of apoptotic cells . Infectious diseases modulate apoptosis and this contributes to disease pathogenesis . Infection with HIV results in enhanced levels of CD4 T-lymphocyte apoptosis in both directly infected cells and in uninfected bystander cells . A variety of HIV proteins including gp120 contribute to this process . A number of different pathways induce HIV-associated CD4 T-lymphocyte apoptosis and apoptosis of uninfected bystander cells is particularly associated with increased susceptibility to Fas . Other viruses including hepatitis viruses and the human herpesviruses also modulate apoptosis . Bacterial infection induces apoptosis which is frequently mediated by the direct activation of caspases in the absence of death receptor ligation . Bacterial induction of apoptosis may either be due to bacterial factors such as the invasin IpaB of Shigella flexneri or be the result of host immune responses which control infection as demonstrated in infections due to Mycobacterium spp . Apoptosis may be modulated by therapeutic strategies, such as antiretroviral therapy, and an improved understanding of infection-associated apoptosis modulation will aid the design of novel therapeutic approaches to control infectious diseases .

J Bacteriol, 2001 Oct, 183(19), 5535 - 43
Nested deletions of the SRL pathogenicity island of Shigella flexneri 2a; Turner SA et al.; In this study, we determined the boundaries of a 99-kb deletable element of Shigella flexneri 2a strain YSH6000 . The element, designated the multiple-antibiotic resistance deletable element (MRDE), had recently been found to contain a 66-kb pathogenicity island (PAI)-like element (designated the SRL PAI) which carries the Shigella resistance locus (SRL), encoding resistance determinants to streptomycin, ampicillin, chloramphenicol, and tetracycline . The YSH6000 MRDE was found to be flanked by two identical IS91 elements present at the S . flexneri homologs of the Escherichia coli genes putA and mdoA on NotI fragment D . Sequence data from two YSH6000-derived MRDE deletants, YSH6000T and S2430, revealed that deletion of the MRDE occurred between the two flanking IS91 elements, resulting in a single IS91 element spanning the two original IS91 loci . Selection for the loss of tetracycline resistance confirmed that the MRDE deletion occurred reproducibly from the same chromosomal site and also showed that the SRL PAI and the SRL itself were capable of independent deletion from the chromosome, thus revealing a unique set of nested deletions . The excision frequency of the SRL PAI was estimated to be 10(-5) per cell in the wild type, and mutation of a P4-like integrase gene (int) at the left end of the SRL PAI revealed that int mediates precise deletion of the PAI.

Mol Microbiol, 2001 Aug, 41(4), 861 - 72
The making of a gradient: IcsA (VirG) polarity in Shigella flexneri; Robbins JR et al.; The generation and maintenance of subcellular organization in bacteria is critical for many cell processes and properties, including growth, structural integrity and, in pathogens, virulence . Here, we investigate the mechanisms by which the virulence protein IcsA (VirG) is distributed on the bacterial surface to promote efficient transmission of the bacterium Shigella flexneri from one host cell to another . The outer membrane protein IcsA recruits host factors that result in actin filament nucleation and, when concentrated at one bacterial pole, promote unidirectional actin-based motility of the pathogen . We show here that the focused polar gradient of IcsA is generated by its delivery exclusively to one pole followed by lateral diffusion through the outer membrane . The resulting gradient can be modified by altering the composition of the outer membrane either genetically or pharmacologically . The gradient can be reshaped further by the action of the protease IcsP (SopA), whose activity we show to be near uniform on the bacterial surface . Further, we report polar delivery of IcsA in Escherichia coli and Yersinia pseudotuberculosis, suggesting that the mechanism for polar delivery of some outer membrane proteins is conserved across species and that the virulence function of IcsA capitalizes on a more global mechanism for subcellular organization.

Carbohydr Res, 2001 Sep 7, 334(4), 315 - 22
Identification and structural analysis of synthetic oligosaccharides of Shigella sonnei using MALDI-TOF MS; Gyemant G et al.; MALDI-TOF mass spectroscopy was used for the molecular weight determination of protected synthetic oligosaccharides related to a cell surface bacterial polysaccharide . By-products containing chlorinated protecting groups caused isotopic patterns characteristic of the natural isotopic distribution of chlorine, were identified on the basis of isotopic distribution . 2,4,6-Trihydroxyacetophenone (THAP) as a matrix was better than 2,5-dihydroxybenzoic acid (DHB) for compounds containing chlorine, since monoisotopic resolution and no fragmentation were observed . In the post source decay (PSD) mode the identification of the oligosaccharide sequence through cleavage of the interglycosidic linkages was also possible, thus providing a sensitive and accurate tool for the structural verification of synthetic oligosaccharide intermediates.

J Infect Dis, 2001 Sep 15, 184(6), 743 - 53 Epub 2001 Aug 24.
Cadaverine prevents the escape of Shigella flexneri from the phagolysosome: a connection between bacterial dissemination and neutrophil transepithelial signaling; Fernandez IM et al.; Shigella flexneri causes bacillary dysentery in humans by invading epithelial cells of the colon, which is characterized by an acute polymorphonuclear leukocyte (PMNL)-rich inflammation . Our recent studies demonstrated that cadaverine, a polyamine, specifically acts to abrogate transepithelial signaling to PMNL induced by S . flexneri . Here, insight is provided into the cellular mechanisms by which cadaverine attenuates the ability of Shigella species to induce PMNL signaling . It was found that cadaverine retards the lysis of the Shigella species-containing vacuole, suggesting that a blockade is established, in which the pathogen is prevented from adequately interacting with the cytoskeleton . Furthermore, an IcsA mutant of S . flexneri that cannot interact with the cytoskeleton and spreads intercellularly fails to induce transmigration of PMNL . Results indicate that cadaverine-induced compartmentalization of Shigella species to the phagolysosome might be a protective response of the host that directly contributes to the diminished ability of PMNL to transmigrate across model intestinal epithelia.

J Food Prot, 2001 Aug, 64(8), 1162 - 5
The effect of temperature and low pH on survival of Shigella flexneri in broth; Zaika LL; The survival characteristics of Shigella fiexneri strain 5348 were determined in brain heart infusion broth as a function of low pH (2 to 5) and temperature (4 to 37 degrees C) . Stationary-phase cells were inoculated into sterile media to give initial populations of 6 to 7 log10 CFU/ml . Bacterial populations were determined periodically by aerobic plate counts . Survivor curves were fitted from plate count data using a two-phase linear model to derive lag times and slopes of the curves, from which D-values and times to a 4-D (99.99%) inactivation (T4D) were calculated . In general, survival increased as temperature decreased and as pH increased . Bacterial populations reached undetectable levels (<1.3 log10 CFU/ml) at 37, 28, 19, 12, and 4 degrees C in media adjusted to pH 4 after 5, 15, 23, 85, and 85 days, respectively, and in media adjusted to pH 3 after 1, 7, 9, 16, and 29 days, respectively . In media adjusted to pH 2, bacterial populations were stable for 2 to 12 h at temperatures of 19 degrees C or lower and reached undetectable levels after 1 to 3 days, while at 28 and 37 degrees C, the bacteria were undetectable after 8 and 2 h, respectively . In media adjusted to pH 5, bacterial levels decreased only 0.5 to 1.5 log10 CFU/ml after 75 days at 4 degrees C and decreased to undetectable levels after 135 days at 12 degrees C, while growth occurred at higher temperatures . These results indicate that S . flexneri is acid resistant and that acidic foods may serve as vehicles for infection.

J Am Med Womens Assoc, 2001 Summer, 56(3), 109 - 12
The risk of infectious diseases among child care providers; Cordell RL; More than 1.1 million people were employed in out-of-home child care facilities in the United States in 1998, and this number is expected to increase over the next 10 years . This group consists primarily of women with a median age of 35 . This review of the literature provides convincing evidence that these women have an excess risk of infection with a number of diseases, including cytomegalovirus, parvovirus B19, and, possibly, giardia . These workers also face an epidemic risk of such other infections as shigellosis, hepatitis A, and cryptosporidiosis . Handwashing, good hygiene, and, where indicated, immunization, remain the mainstays of prevention for this group.

Infect Immun, 2001 Sep, 69(9), 5742 - 51
dksA is required for intercellular spread of Shigella flexneri via an RpoS-independent mechanism; Mogull SA et al.; Pathogenesis of Shigella flexneri is dependent on the ability of the bacterium to invade and spread within epithelial cells . In this study, we identified dksA as a gene necessary for intercellular spread in, but not invasion of, cultured cells . The S . flexneri dksA mutant exhibited sensitivity to acid and oxidative stress, in part due to an effect of DksA on production of RpoS . However, an S . flexneri rpoS mutant formed plaques on tissue culture monolayers, thus excluding DksA regulation of RpoS as the mechanism responsible for the inability of the dksA mutant to spread intercellularly . Intracellular analysis of the dksA mutant indicates that it survived and divided within the Henle cell cytoplasm, but the dksA mutant cells were elongated, and some exhibited filamentation in the intracellular environment . Some of the S . flexneri dksA mutant cells showed aberrant localization of virulence protein IcsA, which may inhibit spread between epithelial cells.

Infect Immun, 2001 Sep, 69(9), 5230 - 4
Predominance of serotype-specific mucosal antibody response in Shigella flexneri-infected humans living in an area of endemicity; Rasolofo-Razanamparany V et al.; The mucosal humoral immune response elicited following Shigella flexneri infection in patients living in Antananarivo districts (Madagascar Island) was evaluated by measuring the gut-derived, circulating immunoglobulin A (IgA) antibody-secreting cells (ASC) specific for the major bacterial antigen lipopolysaccharide (LPS) . Fifty, 34, 11, and 5% of the S . flexneri-positive patients were infected with serotypes 2a, 1a, 4a, and 3a, respectively . The total number of IgA ASC in infected patients increased significantly, compared to the number in healthy controls, early after the onset of disease . The number of anti-homologous LPS IgA ASC varied among individuals and peaked between days 5 and 10 after the onset of the disease . In the S . flexneri 1a- and 2a-infected patients, the level of IgA ASC cross-reactivity to heterologous S . flexneri serotypes was weak . These data indicate that S . flexneri 2a and 1a are the predominant strains responsible for shigellosis in this area of endemicity and that the anti-LPS antibody response following natural infection is mainly directed against serotype-specific determinants.

Phys Rev E Stat Nonlin Soft Matter Phys . 2001 Aug;64(2 Pt 1):021904 . Epub 2001 Jul 19.
Curved tails in polymerization-based bacterial motility; Rutenberg AD et al.; The curved actin "comet-tail" of the bacterium Listeria monocytogenes is a visually striking signature of actin polymerization-based motility . Similar actin tails are associated with Shigella flexneri, spotted-fever Rickettsiae, the Vaccinia virus, and vesicles and microspheres in related in vitro systems . We show that the torque required to produce the curvature in the tail can arise from randomly placed actin filaments pushing the bacterium or particle . We find that the curvature magnitude determines the number of actively pushing filaments, independent of viscosity and of the molecular details of force generation . The variation of the curvature with time can be used to infer the dynamics of actin filaments at the bacterial surface.

Microbios, 2001, 106(413), 31 - 8
Correlation between Congo red binding and contact haemolysin production in Shigella species; Sharma K et al.; Haemolytic strains of Shigella dysenteriae type 1, Shigella flexneri, Shigella boydii and Shigella sonnei cultured on Congo red agar produced pigmented colonies (Pcr+) whereas nonhaemolytic strains produced white colonies and did not bind Congo red (Pcr-) . S . flexneri-1 haemolysin negative mutant (lacking plasmid) of haemolysin positive prototroph also did not bind Congo red and produced nonpigmented colonies . Among the twelve strains of Shigella included in this study, the characteristics of Congo red binding, plasmid profile and haemolytic activity appeared to be correlated . Congo red binding occurred comparatively more by haemolysin-producing strains . Congo red binding can be used as a quick and reliable method for virulence traits of pathogens, including haemolysin activity.

J Med Microbiol, 2001 Aug, 50(8), 667 - 74
Sensitivity and performance characteristics of a direct PCR with stool samples in comparison to conventional techniques for diagnosis of Shigella and enteroinvasive Escherichia coli infection in children with acute diarrhoea in Calcutta, India; Dutta S et al.; As the sensitivity of the conventional techniques for identifying Shigella spp . and enteroinvasive Escherichia coli (EIEC) causing dysentery cases is low, a PCR assay was evaluated in this study . Analytical sensitivity (2 x 10(2) cfu) of the PCR technique was obtained by artificially spiking negative stool samples with a standard strain of S . flexneri type 2, then determining the detection limit . Specificity (100%) of the method was determined by testing a number of known Shigella and EIEC strains and organisms other than Shigella spp . A total of 300 stool samples collected from children with acute diarrhoea was plated on to two selective agar media after enrichment in Luria broth . Shigella spp . were isolated from 7.7% (23 of 300) and EIEC from 1% (3 of 300) patients . All enriched stool samples were subjected to PCR to amplify the target sequence of invasive plasmid antigen (ipa)H locus, a multicopy element found on the chromosome and invasion plasmid . The stool PCR was positive in 24 of the 26 culture-positive and in 22 culture-negative stools, thus detecting the presence of Shigella spp . or EIEC in 15.3% (46 of 300) of diarrhoea cases . When an ial probe was used for colony hybridistion with enriched stool cultures blotted on to membranes, 9.6% (29 of 300) of dysentery cases were identified as being caused by Shigella spp . or EIEC . Thus the sensitivity of enriched stool culture, colony hybridisation and enriched stool PCR was found to be 54%, 60% and 96%, respectively, when each of the methods was compared to the total microbiologically confirmed cases of dysentery . It was also observed that only 38% (48 of 126) of acute bloody dysentery cases actually had shigella or EIEC infection, as confirmed by laboratory methods . Moreover, this PCR assay could identify a number of untypable Shigella strains (Sh OUT), which would have remained undiagnosed had this assay not been used.

Public Health, 2001 Jul, 115(4), 295 - 300
A report of an outbreak of Shigellosis in a primary school in Staffordshire; Parry J et al.; This paper describes the management of an outbreak of Shigellosis, reported in the national media, in a village school in Staffordshire . The issues encountered by the outbreak team during the management of this incident have re-affirmed the need for public and environmental health departments to work closely with educational bodies to develop clear and consistent action plans for the management of communicable disease outbreaks . The management of communicable disease in schools, the workplace and other settings should be addressed, possibly as a component of local health improvement plans.

EMBO Rep, 2001 Aug, 2(8), 736 - 42 Epub 2001 Jul 19.
CARD4/Nod1 mediates NF-kappaB and JNK activation by invasive Shigella flexneri; Girardin SE et al.; Epithelial cells are refractory to extracellular lipopolysaccharide (LPS), yet when presented inside the cell, it is capable of initiating an inflammatory response . Using invasive Shigella flexneri to deliver LPS into the cytosol, we examined how this factor, once intracellular, activates both NF-kappaB and c-Jun N-terminal kinase (JNK) . Surprisingly, the mode of activation is distinct from that induced by toll-like receptors (TLRs), which mediate LPS responsiveness from the outside-in . Instead, our findings demonstrate that this response is mediated by a cytosolic, plant disease resistance-like protein called CARD4/Nod1 . Biochemical studies reveal enhanced oligomerization of CARD4 upon S . flexneri infection, an event necessary for NF-kappaB induction . Dominant-negative versions of CARD4 block activation of NF-kappaB and JNK by S . flexneri as well as microinjected LPS . Finally, we showed that invasive S . flexneri triggers the formation of a transient complex involving CARD4, RICK and the IKK complex . This study demonstrates that in addition to the extracellular LPS sensing system mediated by TLRs, mammalian cells also possess a cytoplasmic means of LPS detection via a molecule that is related to plant disease-resistance proteins.

J Microbiol Immunol Infect, 2001 Jun, 34(2), 103 - 8
Molecular subtyping of Shigella flexneri 3a isolates by plasmid profile analysis and pulsed-field gel electrophoresis; Lin CS et al.; Twenty-two clinical isolates of Shigella flexneri 3a that were obtained from stool specimens from seven outbreaks of infection in northern Taiwan were subtyped and compared using plasmid profile analysis and pulsed-field gel electrophoresis (PFGE) . Among 32 isolates, three distinct patterns were found by plasmid profile analysis and six by PFGE, with three different restriction enzymes, XbaI, SfiI, or NotI . Seven PFGE patterns were observed in a comparative analysis using a combination of these three enzymes . Isolates collected from the same outbreaks had the same PFGE combination patterns and were distinguishable from those obtained during other outbreaks . These findings suggest that PFGE may be the most powerful method of genotyping S . flexneri 3a in epidemiological studies.

J Food Prot, 2001 Jul, 64(7), 975 - 81
Sensitivity of acid-adapted and acid-shocked Shigella flexneri to reduced pH achieved with acetic, lactic, and propionic acids; Tetteh GL et al.; Survival and growth characteristics of unadapted, acid-adapted, and acid-shocked Shigella flexneri 2a cells in acidified (pH 3.5 to 5.5) tryptic soy broth with 0.25% glucose (TSB) and tryptic soy agar (TSA) were determined . S . flexneri was grown at 37 degrees C for 18 h in tryptic soy broth without glucose (TSBNG) (unadapted) and TSBNG supplemented with 1% glucose (TSBG) (acid-adapted) . Cells grown in TSBNG were acid shocked by adjusting 16-h cultures to pH 5.05 +/- 0.05 with lactic acid . Cells were then inoculated into TSB acidified with acetic, lactic, or propionic acids to pH 5.5, 4.5, or 3.5 and incubated at 37 degrees C for 6 h . The order of lethality at a given pH was lactic acid < acetic acid < propionic acid . Significantly (P < or = 0.05) higher numbers of acid-adapted cells, compared to acid-shocked and unadapted cells, were recovered from TSB acidified (pH 3.5) with lactic or acetic acids . None of the cells survived a 30-min exposure in TSB acidified with propionic acid to pH 3.5 . When the three cell types were plated on TSA acidified with lactic, acetic, or propionic acids at pH < or = 4.5, < or = 5.5, and < or = 5.5, respectively, visible colonies were not detected . Viable unadapted, acid-adapted, and acid-shocked cells were, however, recovered from TSA acidified with all three acids at pH > or = 4.5 . Acid-adapted and, to a lesser extent, acid-shocked cells survived at lower pH than did unadapted cells, indicating that prior exposure to mild acidic environment results in increased acid resistance . Survival of S . flexneri at a given pH was influenced by the type of acidulant used, a response characteristic exhibited by other gram-negative enteric pathogens.

S Afr Med J, 2001 May, 91(5), 417 - 21
An outbreak of food poisoning among children attending an international sports event in Johannesburg; Karas JA et al.; OBJECTIVES: To describe an outbreak of food poisoning at a major international sports event in Johannesburg and to determine the likely cause and source of the outbreak . DESIGN: A descriptive, case-control study . SETTING: An international sports event in Johannesburg . METHODS: A questionnaire survey of involved children was used to conduct a case-control study . Microbiological and chemical analysis of the implicated food was undertaken . Site visits to the premises involved in food preparation were conducted . RESULTS: A total of 578 children were involved . Of the 361 children who returned questionnaires, 134 were affected by an acute-onset emetic-type illness, while 53 children developed diarrhoea . Consumption of fruit juice was associated with acute illness, while diarrhoea was associated with the consumption of maize-meal porridge (pap) and chicken stew . Microbiological analysis revealed high bacterial loads in samples of the fruit juice and the presence of Shigella flexneri in the maize-meal porridge . Visits to the suppliers of the implicated foods revealed several deficiencies in terms of food hygiene precautions . CONCLUSION: The likely vehicles and causes of this outbreak are elucidated . Guidelines for monitoring the supply and distribution of food to future similar events should be established . Furthermore, hospitals should have protocols in place to deal with such outbreaks in a manner that facilitates epidemiological investigation.

J Child Neurol, 2001 Jul, 16(7), 539 - 40
Acute encephalopathy associated with nontyphoidal salmonellosis; Arii J et al.; The importance of an acute encephalopathy associated with nontyphoidal salmonellosis has recently been recognized, but the disease entity has been poorly established . In this study, we describe two encephalopathic patients associated with nontyphoidal salmonellosis . The patients exhibited a rapid evolution of coma after the onset of lethargy or seizure . Fever and diarrhea due to salmonellosis preceded these events . Secondary factors inducing encephalopathies, such as severe dehydration, sepsis, meningitis, electrolyte or metabolic disturbances, acute renal failure, and multiple organ failure, were excluded in the differential diagnosis at the onset of encephalopathic features . These clinical findings and rapid development of encephalopathic features from localized intestinal infection without any significant abnormalities in a variety of blood tests may suggest a toxic etiology . However, endotoxin was not found in serum from both patients . From these results, we conclude that nontyphoidal salmonellosis can cause a toxic encephalopathy syndrome, like shigellosis or verocytotoxin-producing Escherichia coli infection.

Transfusion, 2001 Jul, 41(7), 898 - 907
Inverse expression of P(k) and Luke blood group antigens on human RBCs; Cooling LL et al.; BACKGROUND: Luke (LKE) is a high-frequency RBC antigen, related to the P blood group system . A LKE-negative phenotype is found in 1 to 2 percent of donors and may be associated with increased P(k) . Because P(k) and similar glycolipids are receptors for shiga toxin on cell membranes, a LKE-negative phenotype could have implications for infections by Shigella dysenteriae and enterohemorrhagic Escherichia coli . STUDY DESIGN AND METHODS: Volunteer donors (n = 257) were serologically typed for LKE with a LKE MoAb, MC813-70 . LKE-strong-positive, LKE-weak-positive and LKE-negative RBCs were analyzed for P(k), P, LKE, and shiga toxin binding by immunofluorescence flow cytometry, high-performance thin-layer chromatography, scanning densitometry, and high-performance thin-layer chromatography immunostaining . RESULTS: Among Iowa donors, 78.6 percent were LKE-strong-positive, 20.2 percent were LKE-weak-positive, and 1.2 percent were LKE-negative . There was an inverse expression of P(k) and LKE on RBCs . P(k) expression was increased on LKE-negative RBCs and was associated with increased shiga toxin binding . A LKE-active glycolipid was identified in the ganglioside fraction of LKE-strong-positive RBCs . CONCLUSION: A LKE-negative phenotype is associated with increased expression of P(k) on RBCs . Differences in P(k) and LKE expression may play a role in host susceptibility to infection with S . dysenteriae and E . coli.

Int J Med Microbiol, 2001 May, 291(2), 89 - 96
Regulation of virulence gene expression in Shigella flexneri, a facultative intracellular pathogen; Dorman CJ et al.; Shigella flexneri and its close relatives are facultative intracellular pathogens of humans and are the etiological agents of bacillary dysentery . These bacteria secrete proteins that enable them to enter human epithelial cells via an elaborate and fascinating cell biology . This behaviour depends on a complicated regulon of virulence genes, whose expression is controlled in response to a multiplicity of environmental signals . This review describes and attempts to interpret these gene control mechanisms.

Genes Genet Syst, 2001 Apr, 76(2), 111 - 20
Characterization of cryptic flagellin genes in Shigella boydii and Shigella dysenteriae; Tominaga A et al.; Flagellin (fliC) genes of 12 Shigella boydii and five Shigella dysenteriae strains were characterized . Though these strains are nonmotile, the cryptic fliCSB gene, cloned from S . boydii strain C3, is functional for expression of flagellin . It consists of 1,704 bp, and encodes 568 amino acid residues (57,918 Da) . The fliCSD gene from S . dysenteriae strain 16 consists of 1,650 bp encoding 549 amino acid residues (57,591 Da) and contains an IS1 element inserted in its 3' end . The two genes are composed of the 5'-constant, central variable and 3'-constant sequences, like other known fliC genes . The two genes share high homology in nucleotide and amino acid sequences with each other and also with the Escherichia coli fliCE gene, indicating that both genes are closely related to the fliCE gene . Comparison of the central variable sequences of six different fliC genes showed that the fliCSB and fliCSD genes share low homology in amino acid sequence with the other fliC genes, suggesting that they encode antigenic determinants intrinsic to respective subgroups . However, Southern blotting using as probes the central variable sequences of several fliC genes showed that four of 12 S . boydii strains have a fliC gene similar to that of Shigella flexneri, and that among five fliC genes from S . dysenteriae strains, one is similar to that of S . flexneri, two are similar to that of S . boydii, and only one is unique to S . dysenteriae . Some of these variant alleles were verified by immunoblotting with flagellins produced from cloned fliC genes . The presence of variant fliC alleles in S . boydii and S . dysenteriae indicates that subdivision into subgroups does not reflect the ancestral flagella H antigenic relationships . These data will be useful in considering the evolutionary divergence of the Shigella spp..

APMIS, 2001 Mar, 109(3), 228 - 34
Antimicrobial resistance of Shigella sonnei in Korea during the last two decades; Lee JC et al.; Eighty-eight strains of Shigella sonnei isolated in Korea during the period 1980 to 1999 were tested for susceptibility to 13 antimicrobial agents . S . sonnei isolates demonstrated high frequencies of resistance to sulfamethoxazole (97.7%), tetracycline (96.6%), and trimethoprim (95.5%) . S . sonnei isolates from the 1990s were more resistant to nalidixic acid than isolates from the 1980s (100 vs 7.7%), while isolates from the 1990s were more susceptible to chloramphenicol than isolates from the 1980s (0 vs 100%) . Ampicillin-resistant S . sonnei isolates produced the TEM-1 beta-lactamase with a pI of 5.4 . The TEM-1 gene was located on conjugally transferable plasmids in the majority of isolates . S . sonnei isolates were all susceptible to cefotaxime, cefoxitin, ceftazidime, ciprofloxacin, and norfloxacin . These results indicate that cephalosporins and quinolones may be alternative antibiotics for the treatment of S . sonnei infections in Korea.

J Zoo Wildl Med, 2000 Dec, 31(4), 539 - 51
Management of reactive arthritis in a juvenile gorilla (Gorilla gorilla gorilla) with long-term sulfasalazine therapy; Neiffer DL et al.; A juvenile western lowland gorilla (Gorilla gorilla gorilla) experienced recurrent fever, lethargy, diarrhea, and/or arthritis starting at age 6 mo . During an episode at age 15 mo, Shigella sp . was isolated from diarrheic feces . At age 41 mo, reactive arthritis was diagnosed . In addition, the gorilla's growth was retarded . All arthritic attacks were managed symptomatically prior to age 4 yr, at which time a severe episode precipitated the implementation of therapy with sulfasalazine, an arthritis suppressive medication . Examination 27 mo later revealed cessation of progressive joint pathology although the animal exhibited decreased range of motion in most joints . The gorilla has been on sulfasalazine therapy for 4 yr without lameness . Growth has resumed, and there has been no radiographic evidence of progressive joint degeneration . Immunogenetic analysis of whole blood obtained at age 68 mo identified the gorilla major histocompatibility class I allele, Gogo-B*0101, which has limited nucleotide sequence similarity to HLA-B27, an allele associated with postinfection reactive arthritis in humans . Sulfasalazine therapy effectively managed reactive arthritis in this gorilla and should be considered for similarly frequently affected animals . Juvenile gorillas, in populations with a history of clinical shigellosis and/or postdiarrhea arthritis, may benefit from prophylactic sulfasalazine therapy after episodes of bacterial enterocolitis . Sulfasalazine therapy should be considered in all gorillas, juvenile and adult, experiencing confirmed Shigella sp.-associated enterocolitis.

Microb Pathog, 2001 Jul, 31(1), 21 - 7
Analysis of the O-antigen chain length distribution during extracellular and intracellular growth of Shigella flexneri; Varela G et al.; This study has established that there were no changes in the general structure of LPS of Shigella flexneri M90T either when the bacteria grew free in the cytoplasm of the eucaryotic host cell or during extracellular growth in liquid LB medium at 37 degrees C . In both cases there was a similar bi-modal O-antigen chain length distribution with the mean modal values between 1 and 2, and between 11 and 14 subunits . This suggests that the intracellular localization is not a significant stimulus perceived by Shigella to regulate the length of its O-side chains . However, when the bacteria grew under extracellular conditions (liquid medium) at 30 degrees C, even though there were no changes in the modal values, the pattern of the O-antigen chain length distribution of LPS was different, with an increase in the amount of the long chains relative to the short chains .

Appl Environ Microbiol, 2001 Jul, 67(7), 3110 - 4
Glutamate decarboxylase genes as a prescreening marker for detection of pathogenic Escherichia coli groups; Grant MA et al.; The enzyme glutamate decarboxylase (GAD) is prevalent in Escherichia coli but few strains in the various pathogenic E . coli groups have been tested for GAD . Using PCR primers that amplify a 670-bp segment from the gadA and gadB genes encoding GAD, we examined the distribution of the gadAB genes among enteric bacteria . Analysis of 173 pathogenic E . coli strains, including 125 enterohemorrhagic E . coli isolates of the O157:H7 serotype and its phenotypic variants and 48 isolates of enteropathogenic E . coli, enterotoxigenic E . coli, enteroinvasive E . coli, and other Shiga toxin-producing E . coli (STEC) serotypes, showed that gadAB genes were present in all these strains . Among the 22 non-E . coli isolates tested, only the 6 Shigella spp . carried gadAB . Analysis of naturally contaminated water and food samples using a gadAB-specific DNA probe that was labeled with digoxigenin showed that a gadAB-based assay is as reliable as standard methods that enumerate E . coli organisms on the basis of lactose fermentation . The presence of few E . coli cells initially seeded into produce rinsates could be detected by PCR to gadA/B genes after overnight enrichment . A multiplex PCR assay using the gadAB primers in combination with primers to Shiga toxin (Stx) genes stx(1) and stx(2) was effective in detecting STEC from the enrichment medium after seeding produce rinsate samples with as few as 2 CFU . The gadAB primers may be multiplexed with primers to other trait virulence markers to specifically identify other pathogenic E . coli groups.

J Biol Chem, 2001 Aug 24, 276(34), 32071 - 9 Epub 2001 Jun 20.
Shigella protein IpaH(9.8) is secreted from bacteria within mammalian cells and transported to the nucleus; Toyotome T et al.; Various pathogenic bacteria such as Shigella deliver effector proteins into mammalian cells via the type III secretion system . The delivered Shigella effectors have been shown to variously affect host functions required for efficient bacterial internalization into the cells . In the present study, we investigated the IpaH proteins for their ability to be secreted via the type III secretion system and their fate in mammalian cells . Upon incubation in a medium containing Congo red, the bacteria secrete IpaH into the medium, but secretion of IpaH occurs later than that of IpaBCD . Immunofluorescence microscopy indicated that IpaH(9.8) is secreted from intracellular bacteria and transported into the nucleus . On microinjection of the protein, intracellular IpaH(9.8) is accumulated at one place around the nucleus and transported into the nucleus . This movement seems to be dependent on the microtubule network, since nuclear accumulation of IpaH(9.8) is inhibited in cells treated with microtubule-destabilizing agents . In nuclear import assay, IpaH(9.8) was efficiently transported into the nucleus, which was completely blocked by treatment with wheat germ agglutinin . The nuclear transport of IpaH(9.8) does not depend on host cytosolic factors but is partially dependent on ATP/GTP, suggesting that, like beta-catenin, IpaH(9.8) secreted from intracellular Shigella can be transported into the nucleus.

J Bacteriol, 2001 Jul, 183(14), 4176 - 82
The SHI-3 iron transport island of Shigella boydii 0-1392 carries the genes for aerobactin synthesis and transport; Purdy GE et al.; In Shigella boydii 0-1392, genes encoding the synthesis and transport of the hydroxamate siderophore aerobactin are located within a 21-kb iron transport island between lysU and the pheU tRNA gene . DNA sequence analysis of the S . boydii 0-1392 island, designated SHI-3 for Shigella island 3, revealed a conserved aerobactin operon associated with a P4 prophage-like integrase gene and numerous insertion sequences (IS) . SHI-3 is present at the pheU tRNA locus in some S . boydii isolates but not in others . The map locations of the aerobactin genes vary among closely related species . The association of the aerobactin operon with phage genes and mobile elements and its presence at different locations within the genomes of enteric pathogens suggest that these virulence-enhancing genes may have been acquired by bacteriophage integration or IS element-mediated transposition . An S . boydii aerobactin synthesis mutant, 0-1392 iucB, was constructed and was similar to the wild type in tissue culture assays of invasion and intercellular spread.

J Bacteriol, 2001 Jul, 183(13), 3949 - 57
Genetic organization of plasmid ColJs, encoding colicin Js activity, immunity, and release genes; Smajs D et al.; The 5.2-kb ColJs plasmid of a colicinogenic strain of Shigella sonnei (colicin type 7) was isolated and sequenced . pColJs was partly homologous to pColE1 and to pesticin-encoding plasmid pPCP1, mainly in the rep, mob, and cer regions . A 1.2-kb unique region of pColJs showed significantly different G+C content (34%) compared to the rest of pColJs (53%) . Within the unique region, seven open reading frames (ORFs) were identified . ORF94 was shown to code for colicin Js activity (cja), a 94-amino-acid polypeptide (molecular mass, 10.4 kDa); ORF129 (cji) was shown to code for the 129-amino-acid colicin Js immunity protein (molecular mass, 14.3 kDa); and ORF65 was shown to be involved in colicin Js release by producer bacteria (cjl) coding for a 65-amino-acid polypeptide (molecular mass, 7.5 kDa) . In contrast to the gene order in other colicin operons, the cjl gene was found upstream from cja . Moreover, the promoter upstream from cjl was similar to promoters described upstream from several colicin activity genes . The cji gene was found to be located downstream from cja with a transcription polarity opposite to that of the cjl and cja genes . The cja, cji, and cjl genes were not similar to other known colicin genes . Colicin Js was purified as an inactive fusion protein with an N-terminal histidine tag . Activity of the purified fusion form of colicin Js was restored after cleavage of the amino acids fused to the colicin Js N terminus.

Hybridoma, 2001 Apr, 20(2), 85 - 90
Characterization of monoclonal antibodies with specificity for the core oligosaccharide of Shigella lipopolysaccharide; Rahman SR et al.; Monoclonal antibodies (MAbs) were prepared against different strains of Shigella, following immunization of BALB/c mice with a heat-killed preparation of Shigella . Antibody-producing hybridomas were screened in an indirect enzyme-linked immunoadsorbent assay (ELISA) and epitope specificity determined using chemically defined lipopolysaccharide, lipid, and KDO fragments . Five MAbs were characterized and the following specificities identified: 2C32E6 and 4D64B9 (reactive to S . flexneri and S . boydii), 5E45D8 (reactive with S . flexneri), 4B33D10 and 1B52F10 (all species of Shigella) . The properties of 1B52F10 revealed its potential importance in immunological detection of Shigella from unknown samples, as it was able to bind to all strains of Shigella.

Emerg Infect Dis, 2001 May-Jun, 7(3), 442 - 3
Third-generation cephalosporin resistance in Shigella sonnei, Argentina; Radice M et al.; Shigella sonnei resistant to cefotaxime (but not to ceftazidime) was isolated for the first time in stool samples from a pediatric patient with vomiting and bloody diarrhea in northern Argentina . Microbiologic and biochemical tests confirmed the presence of an extended spectrum beta-lactamase displaying an apparent isoelectric point value of 8.2.

Curr Microbiol, 2001 Jun, 42(6), 381 - 7
Adherence of Shigella dysenteriae 1 to human colonic mucin; Sudha PS et al.; The pathogenic potential of Shigella is correlated with the ability of the organism to invade and multiply within the cells of colonic epithelium . Although invasion is the ultimate event, a preceding step is adherence . Shigella dysenteriae 1 preferentially adhered to colonic mucin and not to small intestinal mucin . The pathogen showed a very strong adherence pattern to human colonic mucin when compared with guinea pig and rat mucin . The adherence pattern of S . dysenteriae 1 was not altered on preincubation with monosaccharides present in mucins, suggesting that the receptor for the pathogen is not a simple sugar . Binding of S . dysenteriae 1 to human colonic mucin was not by weak hydrophobic forces . The bacterium also adhered to glycolipids, emphasizing the role of glycoconjugates as receptors for S . dysenteriae 1.

Microbiol Mol Biol Rev, 2001 Jun, 65(2), 232 - 60 ; second page, table of contents
Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance; Chopra I et al.; Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites . They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters . The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953 . Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria . The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease . Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines . Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing . A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA . New tetracycline derivatives are being examined, although their role in treatment is not clear . Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.

Science, 2001 May 25, 292(5521), 1502 - 6
Mechanism of actin-based motility; Pantaloni D et al.; Spatially controlled polymerization of actin is at the origin of cell motility and is responsible for the formation of cellular protrusions like lamellipodia . The pathogens Listeria monocytogenes and Shigella flexneri, which undergo actin-based propulsion, are acknowledged models of the leading edge of lamellipodia . Actin-based motility of the bacteria or of functionalized microspheres can be reconstituted in vitro from only five pure proteins . Movement results from the regulated site-directed treadmilling of actin filaments, consistent with observations of actin dynamics in living motile cells and with the biochemical properties of the components of the synthetic motility medium.

Microbes Infect, 2001 May, 3(6), 493 - 507
Effect of Shiga toxin and Shiga-like toxins on eukaryotic cells; O'Loughlin EV et al.; Shigella dysenteriae and Shiga-toxin-producing Escherichia coli (STEC) elaborate the AB holotoxins, Shiga or Shiga-like toxins (Stx) . Stx play a major role in the pathogenesis of haemorrhagic colitis and haemolytic uremic syndrome . This review provides an overview of the mechanisms of action of Stx and a model of the pathogenesis of Stx-induced disease.

Arch Biochem Biophys, 2001 Mar 1, 387(1), 137 - 42
The ShuS protein of Shigella dysenteriae is a heme-sequestering protein that also binds DNA; Wilks A; The ability of Shigella dysenteriae to utilize heme as an iron source is dependent on the iron-regulated expression of a number of genes including the outermembrane receptor ShuA and the cytoplasmic protein ShuS . The ShuS protein has no sequence homology with any proteins of known function and its role in heme acquisition has not been determined . In this paper we describe the purification and characterization of ShuS . The soluble oligomeric protein (650 kDa) is composed of a single type of subunit with a molecular mass of 37 kDa and binds one heme per monomer (Kd = 13 microM) . In addition, the ShuS protein was shown to nonspecifically bind double-stranded DNA . It appears, therefore, that ShuS may function as both a heme storage protein, during periods of active heme transport, and as a DNA binding protein to protect the DNA from any ensuing heme mediated oxidative damage.

Pediatr Infect Dis J, 2001 May, 20(5), 525 - 30
Epidemiology of postshigellosis persistent diarrhea in young children; Ahmed F et al.; BACKGROUND: Dysentery accounts for 20% of the 4.6 million diarrhea-associated deaths among children in developing countries, with the risk from death in dysenteric persistent diarrhea 10-fold higher than that in acute dysentery . Although Shigella accounts for the majority of dysenteric episodes, very little is known about the epidemiology of postshigellosis persistent diarrhea . METHODS: Rural Bangladeshi children younger than 5 years of age (n = 1,756) were followed for 1 month after exposure to sentinel cases of Shigella dysentery . The likelihood of an acute diarrheal episode becoming persistent was assessed . RESULTS: Diarrhea caused by Shigella was significantly associated with an increased risk of persistent diarrhea (age-adjusted relative risk, 1.83; 95% confidence interval, 1.19 to 2.81) . Despite the use of nalidixic acid in dysenteric episodes, persistent diarrhea occurred in 23% of children with shigellosis . Infection by multiply antibiotic-resistant Shigella isolates (age-adjusted relative risk, 3.76; 95% confidence interval, 1.51 to 9.36) and occurrence of shigellosis during infancy were observed to be risk factors for initiation of Shigella diarrhea persistence . However, 88% of the persistent shigellosis episodes occurred in older children, 50% were associated with nondysenteric shigellosis and 79% were caused by Shigella species other than Shigella dysenteriae 1 . CONCLUSIONS: These data demonstrate the importance of Shigella as a cause of persistent diarrhea and indicate that strategies to prevent postshigellosis persistent diarrhea must be broad-based, with a focus on older children as well as infants, management of nondysenteric as well as dysenteric disease and prevention of diarrhea caused by multiple Shigella species.

Infect Immun, 2001 Jun, 69(6), 4027 - 33
EspG, a novel type III system-secreted protein from enteropathogenic Escherichia coli with similarities to VirA of Shigella flexneri; Elliott SJ et al.; The function of the rorf2 gene located on the locus of enterocyte effacement (LEE) pathogenicity island of enteropathogenic Escherichia coli (EPEC) has not been described . We report that rorf2 encodes a novel protein, named EspG, which is secreted by the type III secretory system and which is translocated into host epithelial cells . EspG is homologous with Shigella flexneri protein VirA, and the cloned espG (rorf2) gene can rescue invasion in a Shigella virA mutant, indicating that these proteins are functionally equivalent in Shigella . An EPEC espG mutant had no apparent defects in in vitro assays of virulence phenotypes, but a rabbit diarrheagenic E . coli strain carrying a mutant espG showed diminished intestinal colonization and yet diarrheal attack rates similar to those of the wild type . A second EspG homolog, Orf3, is encoded on the EspC pathogenicity islet . The cloned orf3 gene could also rescue invasion in a Shigella virA mutant, but an EPEC espG orf3 double mutant was not diminished in any tested in vitro assays for EPEC virulence factors . Our results indicate that EspG plays an accessory but as yet undefined role in EPEC virulence that may involve intestinal colonization.

Folia Microbiol (Praha), 2000, 45(4), 301 - 4
New O and H antigens of the international antigenic scheme for Plesiomonas shigelloides; Aldova E et al.; A revised update of the International antigenic scheme for Plesiomonas shigelloides is presented . Twenty-six new O (O77-O102) and 10 new H (H42-H50 and H1a1d) antigens have been described since 1994 . The sources of antigens are mostly human clinical strains, isolates from warmblooded animals and a few environmental cultures.

Nat Cell Biol, 2001 May, 3(5), 484 - 91
WIP regulates N-WASP-mediated actin polymerization and filopodium formation; Martinez-Quiles N et al.; Induction of filopodia is dependent on activation of the small GTPase Cdc42 and on neural Wiskott-Aldrich-syndrome protein (N-WASP) . Here we show that WASP-interacting protein (WIP) interacts directly with N-WASP and actin . WIP retards N-WASP/Cdc42-activated actin polymerization mediated by the Arp2/3 complex, and stabilizes actin filaments . Microinjection of WIP into NIH 3T3 fibroblasts induces filopodia; this is inhibited by microinjection of anti-N-WASP antibody . Microinjection of anti-WIP antibody inhibits induction of filopodia by bradykinin, by an active Cdc42 mutant (Cdc42(V12)) and by N-WASP . Our results indicate that WIP and N-WASP may act as a functional unit in filopodium formation, which is consistent with their role in actin-tail formation in cells infected with vaccinia virus or Shigella.

Sheng Wu Gong Cheng Xue Bao, 2001 Jan, 17(1), 29 - 33
{Immunologic properties of coli surface antigen 6(CS6) of enterotoxigenic Escherichia coli and cholera toxin subunit B expressed in Shigella flexneri 2a strain T32}; Ying TY et al.; A host-plasmid balancing system composed with a delta asd mutant (FaD) of an avirulent strain (T32) of Shigella flexneri 2a and plasmid harboring asd gene was used to express enterotoxigenic E . coli surface antigen 6(CS6) and V . cholerae toxin subunit B (CTB) . The results of Western blotting and ELISA showed that all of recombinant plasmids (pYX201, pYX202 and pYX203) could be maintained stably and expressed CS6 and CTB respectively in T32 without any antibiotic selection . All the recombinant bacterial strains could elicit the corresponding antibodies in rabbits . The antibodies against CTB elicited by both FaD/pYX201 and FaD/pYX203 showed to be high level, and had long prolongation time, in otherwise, the antibodies against CS6 showed to be low level, indicating that higher expression level of foreign antigen may be benefit for construction of genetic multivalent vaccine.

J Antimicrob Chemother, 2001 May, 47(5), 685 - 8
SHV-type extended-spectrum beta-lactamase in a Shigella flexneri clinical isolate; Fortineau N et al.; A Shigella flexneri isolate resistant to oxyimino-cephalosporins was recovered from a stool sample of a 16 month-old Algerian child hospitalized in Paris, France . This isolate harboured an SHV-2 beta-lactamase gene located on a c . 80 kb self-transferable plasmid . This is the first report of an Ambler class A extended-spectrum beta-lactamase from Shigella spp.

Plasmid, 2001 Mar, 45(2), 88 - 100
pUb6060: a broad-host-range, DNA polymerase-I-independent ColE2-like plasmid; Avison MB et al.; A ColE2-like, cryptic plasmid, pUB6060, of 5.8 kb has been found in a clinical isolate of Plesiomonas shigelloides . The complete sequence of pUB6060 has been determined and reveals a number of interesting features about the plasmid . The ColE2-like replication locus is linked to a functional ColE1-like mobilization locus . Replication is, unusually for ColE2 replicons, DNA polymerase-I-independent and may involve two, rather than the usual one, plasmid-encoded functions . Additionally, it carries two ORFs encoding products of unknown function . The pUB6060 replicon maintains a moderate plasmid copy number (10 per chromosome copy) and permits replication in diverse gram-negative bacteria .

Eur J Clin Microbiol Infect Dis, 2001 Feb, 20(2), 123 - 6
Prospective cohort studies of shigellosis during military field training; Cohen D et al.; Epidemiological and clinical features of shigellosis occurring among cohorts of Israeli recruits followed-up for 3-6 months during the summer field training of years 1993-1997 were studied . The incidence rate of culture-proven shigellosis was the highest (78 cases per 1,000 recruits) in 1996 and the lowest (13 cases per 1,000 recruits) in 1995 . Shigella sonnei (152 isolates) and Shigella flexneri (151 isolates) were the most common species . Fifty percent of the patients with shigellosis had fever (>37.5 degrees C), compared to only 18% of the subjects with other diarrheal diseases (P < 0.001) . The duration of illness was longer among subjects with shigellosis than among those with other diarrheal diseases (P < 0.001) . Illness due to Shigella flexneri was more severe than illness caused by Shigella sonnei.

Mikrobiol Z, 2000 Jan-Feb, 62(1), 64 - 72
{Immunosuppressive properties of virulent Shigella strains}; Borisova EB; The review presents data which show the existence of significant difference between the virulent and avirulent Shigella species . This difference is displayed in the virulent Shigella's ability to inhibit immune memory and secondary immune response . The existance of immunosuppressive activity in virulent Shigella has been demonstrated in the case of experimental Shigella infection in animals as well as natural infection in humans . The immunosuppressive property of Shigella sonnei is determined by the invasiveness genes of the virulence plasmid . Lipopolysaccharide (LPS) from virulent Shigella sonnei differs from the avirulent Shigella sonnei LPS . It possesses the property to induce in avirulent bacteria the ability to inhibit secondary immune response . This inductive immunosuppressive property of LPS is also encoded by invasiveness genes . Thus, literature data suggest that the ability to inhibit immune memory, secondary immune response and the existence of inductive immunosuppressive property in LPS are Shigella's signs of virulence as well as its ability to invade epithelial cells.

J Appl Microbiol, 2001 Mar, 90(3), 482 - 7
Effects of medium composition, calcium, iron and oxygen on haemolysin production by Plesiomonas shigelloides isolated from water; Baratela KC et al.; AIMS: The effects of medium composition, calcium, iron and oxygen tension on the haemolytic activity of Plesiomonas shigelloides were investigated . METHODS AND RESULTS: The haemolytic activity of seven strains of Ple . shigelloides was tested on the surface of Luria Agar (LA), Brain Heart Infusion Agar (BHIA) and Trypitic Soy Agar (TSA) containing 5% (v/v) sheep blood, and in the Agar Overlay (AO) assay . All strains produced beta-haemolysis in the AO assay in three media, and on the surface of LA . The kinetics of growth and haemolytic activity of Ple . shigelloides 9P3-1 were evaluated in six different media, and the highest production of haemolysin occurred in Luria Broth (LB) . The haemolytic activity of 9P3-1 was stimulated by Ca2+ and inhibited by EDTA . Addition of iron to the culture medium did not affect bacterial growth, although it reduced bacterial haemolytic activity . In the presence of an iron chelator, growth of the 9P3-1 was inhibited, but its haemolytic activity was enhanced . CONCLUSION: The haemolytic activity of Ple . shigelloides depends on medium composition, and that it is regulated by iron and is calcium-dependent . SIGNIFICANCE AND IMPACT OF THE STUDY: These results show the importance of optimization of media composition and oxygen tension for detection of Ple . shigelloides haemolytic activity.

Int J Food Microbiol, 2001 Mar 20, 64(3), 343 - 54
Microbial growth modelling with artificial neural networks; Jeyamkonda S et al.; There is a growing interest in modelling microbial growth as an alternative to time-consuming, traditional, microbiological enumeration techniques . Several statistical models have been reported to describe the growth of different microorganisms, but there are accuracy problems . An alternate technique 'artificial neural networks' (ANN) for modelling microbial growth is explained and evaluated . Published data were used to build separate general regression neural network (GRNN) structures for modelling growth of Aeromonas hydrophila, Shigella flexneri, and Brochothrix thermosphacta . Both GRNN and published statistical model predictions were compared against the experimental data using six statistical indices . For training data sets, the GRNN predictions were far superior than the statistical model predictions, whereas the GRNN predictions were similar or slightly worse than statistical model predictions for test data sets for all the three data sets . GRNN predictions can be considered good, considering its performance for unseen data . Graphical plots, mean relative percentage residual, mean absolute relative residual, and root mean squared residual were identified as suitable indices for comparing competing models . ANN can now become a vehicle whereby predictive microbiology can be applied in food product development and food safety risk assessment.

J Bacteriol, 2001 May, 183(9), 2715 - 23
Characterization of the Plesiomonas shigelloides genes encoding the heme iron utilization system; Henderson DP et al.; Plesiomonas shigelloides is a gram-negative pathogen which can utilize heme as an iron source . In previous work, P . shigelloides genes which permitted heme iron utilization in a laboratory strain of Escherichia coli were isolated . In the present study, the cloned P . shigelloides sequences were found to encode ten potential heme utilization proteins: HugA, the putative heme receptor; TonB and ExbBD; HugB, the putative periplasmic binding protein; HugCD, the putative inner membrane permease; and the proteins HugW, HugX, and HugZ . Three of the genes, hugA, hugZ, and tonB, contain a Fur box in their putative promoters, indicating that the genes may be iron regulated . When the P . shigelloides genes were tested in E . coli K-12 or in a heme iron utilization mutant of P . shigelloides, hugA, the TonB system genes, and hugW, hugX, or hugZ were required for heme iron utilization . When the genes were tested in a hemA entB mutant of E . coli, hugWXZ were not required for utilization of heme as a porphyrin source, but their absence resulted in heme toxicity when the strains were grown in media containing heme as an iron source . hugA could replace the Vibrio cholerae hutA in a heme iron utilization assay, and V . cholerae hutA could complement a P . shigelloides heme utilization mutant, suggesting that HugA is the heme receptor . Our analyses of the TonB system of P . shigelloides indicated that it could function in tonB mutants of both E . coli and V . cholerae and that it was similar to the V . cholerae TonB1 system in the amino acid sequence of the proteins and in the ability of the system to function in high-salt medium.

Infect Immun, 2001 May, 69(5), 3271 - 85
Complete DNA sequence and analysis of the large virulence plasmid of Shigella flexneri; Venkatesan MM et al.; The complete sequence analysis of the 210-kb Shigella flexneri 5a virulence plasmid was determined . Shigella spp . cause dysentery and diarrhea by invasion and spread through the colonic mucosa . Most of the known Shigella virulence determinants are encoded on a large plasmid that is unique to virulent strains of Shigella and enteroinvasive Escherichia coli; these known genes account for approximately 30 to 35% of the virulence plasmid . In the complete sequence of the virulence plasmid, 286 open reading frames (ORFs) were identified . An astonishing 153 (53%) of these were related to known and putative insertion sequence (IS) elements; no known bacterial plasmid has previously been described with such a high proportion of IS elements . Four new IS elements were identified . Fifty putative proteins show no significant homology to proteins of known function; of these, 18 have a G+C content of less than 40%, typical of known virulence genes on the plasmid . These 18 constitute potentially unknown virulence genes . Two alleles of shet2 and five alleles of ipaH were also identified on the plasmid . Thus, the plasmid sequence suggests a remarkable history of IS-mediated acquisition of DNA across bacterial species . The complete sequence will permit targeted characterization of potential new Shigella virulence determinants.

Infect Immun, 2001 May, 69(5), 3240 - 7
Shigella infection in a SCID mouse-human intestinal xenograft model: role for neutrophils in containing bacterial dissemination in human intestine; Zhang Z et al.; Shigellae infect human intestine and cause intense inflammation and destruction of colonic and rectal mucosa . To model the interactions of shigella with human intestine in vivo, we have studied shigella infection in human intestinal xenografts in severe combined immunodeficient mice (SCID-HU-INT mice) . Inoculation of shigella into human intestinal xenografts caused severe inflammation and mucosal damage, which was apparent as soon as 4 h following infection . Shigella infection was associated with human intestinal production of interleukin-1B (IL-1B) and IL-8 and a marked neutrophil influx into the graft . Depletion of neutrophils from SCID-HU-INT mice reduced inflammation in the human intestinal xenograft in response to shigella infection but failed to significantly alter tissue damage . However, the number of intracellular bacteria was more than 20-fold higher in the human intestinal xenografts from neutrophil-depleted SCID-HU-INT mice . Infection of human intestinal xenografts with an attenuated vaccine strain of shigella (CVD1203) induced lower levels of IL-1B and IL-8 than wild-type shigella and caused only moderate damage to the intestinal permeability barrier . Our studies establish the SCID-HU-INT mouse as a viable model for studying the interactions between shigella and human intestine and indicate that neutrophils are important for controlling the invasion of human intestine by shigella.

Infect Immun, 2001 May, 69(5), 3150 - 8
Attenuated Shigella flexneri 2a Delta guaBA strain CVD 1204 expressing enterotoxigenic Escherichia coli (ETEC) CS2 and CS3 fimbriae as a live mucosal vaccine against Shigella and ETEC infection; Altboum Z et al.; To construct a prototype hybrid vaccine against Shigella and enterotoxigenic Escherichia coli (ETEC), the genes encoding the production of ETEC CS2 and CS3 fimbriae were isolated and expressed in attenuated Shigella flexneri 2a guaBA strain CVD 1204 . The CS2 cotA to -D genes, isolated from ETEC strain C91F, and the CS3 cstA to -H genes, subcloned from plasmid pCS100, were cloned into ~15-copy-number-stabilized pGA1 behind the osmotically regulated ompC promoter, resulting in high expression of both fimbriae . Under nonselective in vitro growth conditions, pGA1-CS2 and pGA1-CS3 were stable in CVD 1204, exhibiting a plasmid loss of only approximately 1% per duplication . Expression of CS2 and CS3 reduced the invasiveness of Shigella for HeLa cells and slowed the intracellular growth rate . Guinea pigs immunized intranasally with CVD 1204(pGA1-CS2) or CVD 1204(pGA1-CS3), or with a mixture of these strains, developed secretory immunoglobulin A (IgA) in tears and serum IgG antibodies against Shigella lipopolysaccharide, CS2, and CS3 antigens . Moreover, the animals were protected against keratoconjunctivitis following conjunctival challenge with virulent S . flexneri 2a strain 2457T . Animals immunized with Shigella expressing CS2 or CS3 developed serum antibodies that agglutinated Shigella as well as an ETEC strain bearing the homologous fimbriae, whereas animals immunized with combined CVD 1204(pGA1-CS2) and CVD 1204(pGA1-CS3) developed antibodies that agglutinated all three test strains . These observations support the feasibility of a multivalent vaccine against shigellosis and ETEC diarrhea consisting of multiple Shigella live vectors expressing relevant ETEC antigens.

Microbiology, 2001 Apr, 147(Pt 4), 851 - 60
Type IV O antigen modification genes in the genome of Shigella flexneri NCTC 8296; Adams MM et al.; The genes encoding type IV O antigen glucosylation were characterized from both Escherichia coli and Shigella flexneri . The putative O antigen modification genes from E . coli, o120 o306 o443, were PCR-amplified and introduced into S . flexneri serotype Y strain SFL124 . Immunogold labelling and phage sensitivity indicated the presence of both serotype Y and serotype 4a O antigens on the cell surface of the resulting recombinant SFL124 strains, suggesting that only partial serotype conversion was conferred by the E . coli genes . The type IV O antigen modification genes were then isolated and characterized from S . flexneri serotype 4a strain NCTC 8296 . A 3.8 kb chromosomal fragment conferred complete conversion to serotype 4a when introduced into SFL124 . Sequence analysis of the fragment revealed the presence of three genes, gtrA(IV) gtrB(IV) gtrIV(Sf) . DNAs homologous to bacteriophage int and attP were located upstream of gtrA(IV), suggesting that this region of the NCTC 8296 genome may have originated from a bacteriophage; however, a serotype-converting phage could not be induced from this strain nor from other strains used in this study . Comparison of the GtrIV(Sf) and GtrIV(Ec) (o443) proteins revealed that they are 41% identical and 63% similar, which is the highest degree of similarity reported among the S . flexneri O antigen glucosyltransferases.

Res Microbiol, 2001 Jan-Feb, 152(1), 47 - 55
Computer identification of Shigella species by rRNA gene restriction patterns; Coimbra RS et al.; We describe a MluI ribotyping scheme for Shigella which approaches correlation with serotyping . One hundred and seventeen reference strains and previously serotyped clinical isolates representing the 57 Shigella serotypes and biotypes were included in this study . A total of 51 distinct ribotypes were obtained and a database was built with them . The number of bands composing each ribotype varied from 9 to 15 . The fragments ranged in size from 1.6 to 18.8 kbp . One hundred and eleven clinical isolates were successfully identified in a double blind study with standard biochemical/serologic methods, by automatic comparison of their ribotypes with our database using the software Taxotron.

Clin Nephrol, 2001 Feb, 55(2), 133 - 42
Re-evaluating criteria for peritoneal dialysis in "classical" (D+) hemolytic uremic syndrome; Bhimma R et al.; BACKGROUND: Indications for peritoneal dialysis in children with post-dysenteric hemolytic uremic syndrome (D+ HUS) have not been thoroughly evaluated . Although early institution of dialysis may reduce mortality, the procedure has attendant complications . AIM: To determine whether the use of more stringent criteria for instituting dialysis had a better outcome to that of using conventional criteria . METHOD: Following an outbreak of Shigella dysenteriae type 1 D+ HUS in KwaZulu/Natal during June 1994 to October 1995, we compared the renal outcome and mortality between two periods: before May 1995 (69 children) when conventional criteria for dialysis were employed and after May 1995 (70 children) when more stringent criteria for dialysis were applied . RESULTS: The mean age of presentation was 35 months, 79 (56.8%) were males . Both groups were comparable except for gut perforation, which was more frequent before May 1995, and hypertension and severe disease, which were more frequent after May 1995 . Seventy patients underwent dialysis, 36 (52.2%) before May 1995 . There were no significant differences in renal outcome or death following discharge from hospital in both groups . Overall mortality was 20.1%, 15 (53.6%) of the 28 children that demised presented before May 1995 . OUTCOME: Accordingly, although children with more severe disease and a higher frequency of hypertension presented after May 1995, there were no significant differences in morbidity or mortality in those using stringent criteria for dialysis, compared to those in whom conventional criteria were used . CONCLUSION: We showed that several children, who would previously have been dialyzed, may be managed conservatively, without an increase in mortality or morbidity.

Emerg Infect Dis, 2001 Jan-Feb, 7(1), 137 - 40
Shigella spp . surveillance in Indonesia: the emergence or reemergence of S . dysenteriae; Subekti D et al.; From June 1998 through November 1999, Shigella spp . were isolated in 5% of samples from 3,848 children and adults with severe diarrheal illness in hospitals throughout Indonesia . S . dysenteriae has reemerged in Bali, Kalimantan, and Batam and was detected in Jakarta after a hiatus of 15 years.

Infect Immun, 2001 Apr, 69(4), 2260 - 9
Plesiomonas shigelloides enters polarized human intestinal Caco-2 cells in an in vitro model system; Theodoropoulos C et al.; This study provides the first definitive evidence that the gram-negative bacterium Plesiomonas shigelloides adheres to and enters eukaryotic intestinal host cells in vitro . P . shigelloides is increasingly regarded as an emerging enteric pathogen and has been implicated in intestinal and extraintestinal infections in humans . However, the establishment of its true role in enteric disease has been hindered by inadequacies in experimental design, deficiencies in clinical diagnosis, and the lack of an appropriate animal model . In this investigation, an in vitro system was used to evaluate plesiomonad pathogenesis . Differentiated epithelium-derived Caco-2 cell monolayers inoculated apically with 12 isolates of P . shigelloides from clinical (intestinal) origins were examined at high resolution using transmission electron microscopy . Bacterial cells were observed adhering to intact microvilli and to the plasma membrane on both the apical and the basal surfaces of the monolayer . The bacteria entered the Caco-2 cells and were observed enclosed in single and multiple membrane-bound vacuoles within the host cell cytoplasm . This observation suggests that initial uptake may occur through a phagocytic-like process, as has been documented for many other enteropathogens . P . shigelloides also was noted free in the cytosol of Caco-2 cells, suggesting escape from cytoplasmic vacuoles . Differences in invasion phenotypes were revealed, suggesting the possibility that, like Escherichia coli, P . shigelloides comprises different pathogenic phenotypes.

Infect Immun, 2001 Apr, 69(4), 2180 - 9
Spa33, a cell surface-associated subunit of the Mxi-Spa type III secretory pathway of Shigella flexneri, regulates Ipa protein traffic; Schuch R et al.; The Mxi-Spa type III secretion system of Shigella flexneri directs the host cell contact-induced secretion of a set of invasins, referred to as Ipas . In this study, we examined the role of Spa33 in Ipa secretion . A spa33-null mutant was both noninvasive and unable to translocate the Ipas from inner membrane to outer membrane (OM) positions of the Mxi-Spa transmembrane channel . Spa33 was found to be a Mxi-Spa substrate that is translocated to the bacterial cell surface upon the induction of Ipa secretion . This mobility may serve to drive Ipa translocation within Mxi-Spa toward OM positions . Consistent with a second distinct role in regulating Ipa traffic, the overexpression of Spa33 also blocked Ipa secretion and resulted in Ipa accumulation at the OM . Co-overexpression of Spa33 and another OM-associated element, Spa32, did not disrupt Ipa secretion, suggesting an interaction between the two proteins and an effect on the mechanism which serves to regulate Ipa release from the OM . These findings indicate that Spa33 is a mobile element within Mxi-Spa, which is required to control Ipa translocation into and out of OM positions of the secretory structure.

Med Klin (Munich), 2001 Feb 15, 96(2), 109 - 13
{Gastroenteritis due to Plesiomonas shigelloides--rare cases in the Western world}; Knebel U et al.; BACKGROUND: Plesiomonas shigelloides is a common pathogen in tropical regions, whereas it is rarely isolated in temperate climates . It is most often found in surface water and fish . During the last 10 years it was found to cause gastroenteritis 6 times in Ludwigshafen . Not all of these patients reported a trip to foreign countries . CASE REPORT: A 54-year-old male patient was hospitalized after a trip to Malaysia with strong greenish watery diarrhea and chills . On physical examination we saw a dehydrated patient in severely reduced general condition . The stool frequency was 30/d . The laboratory examinations only showed elevated parameters of inflammation . Plesiomonas shigelloides was cultivated in the stool cultures . With appropriate substitution of fluid and electrolytes, and antidiarrheal therapy the patient resumed a normal diet without any complications . Three days later his bowel movements were normal and his general condition was greatly improved . We withheld antibiotic therapy because of the noncomplicated course of illness . CONCLUSION: In Germany infections with Plesiomonas shigelloides are rare, an increase is observed because of increasing tourism to tropical regions . The course of infection is sometimes asymptomatic, but usually patients develop an acute gastroenteritis . Especially immunocompromised patients can show serious courses of infection . Plesiomonas shigelloides should be included in the differential diagnosis of acute gastroenteritis after journeys to tropical regions . Some of our patients, however, denied traveling to tropical regions . They also denied consuming seafood, which indicates a risk of infection in Germany . Still an infection with Plesiomonas shigelloides seems to be rare in northern European countries.

J Antimicrob Chemother, 1999 Feb, 43(2), 195 - 201
Impaired imipenem uptake associated with alterations in outer membrane proteins and lipopolysaccharides in imipenem-resistant Shigella dysenteriae; Ghosh AS et al.; Three imipenem-resistant mutants were obtained from a clinical isolate (C152) of Shigella dysenteriae by selection with increasing concentrations of imipenem . Resistance to imipenem was associated with resistance to several other beta-lactam antibiotics . The penicillin-binding protein (PBP) patterns of the resistant and the wild-type strains were comparable . The permeability of the outer membrane proteins (OMPs) of the most resistant mutant, IM16, was lower than that of the parent strain C152 when imipenem and arabinose were used as test solutes . This mutant had lower levels of both the major OMPs of M(r) 43,000 and 38,000 . There were also differences in the patterns of lipopolysaccharide (LPS) of the mutants and the wild-type strain . The mutant IM16 had less short-chain LPS than the parent C152 . Increasing imipenem resistance was also associated with a concomitant decrease in the level of 2-keto-3-deoxyoctonate, a component of the core region of LPS.

Zh Mikrobiol Epidemiol Immunobiol, 2001 Jan-Feb, (1), 75 - 7
{Correction of immunologic reactivity depending on ABO system antigens in patients with purulent infections of soft tissue and shigellosis}; Zemskov AM et al.; The immunological study of more than 300 patients with purulent infection of soft tissues and shigellosis was carried out . The character and manifestation of the immunocorrecting action of sodium nucleinate were found to depend on the antigens of the AB0 system, which proved to be different in various type of pathology.

Water Res, 2001 Mar, 35(4), 869 - 74
A sensitive seminested PCR method for the detection of Shigella in spiked environmental water samples; Theron J et al.; A rapid seminested polymerase chain reaction (PCR) method for the specific, sensitive detection of virulent Shigella spp . in spiked environmental water samples was developed . A set of primers specific for the invasion plasmid antigen gene (ipaH) of virulent Shigella spp . and enteroinvasive Escherichia coli produced a 620-bp fragment that was used as template for the seminested primer pair delineating a 401-bp fragment . By using agarose gel electrophoresis for detection of the seminested PCR-amplified products, a detection limit of 1.6 x 10(3) cfu S . flexneri was obtained with amplification reactions from crude bacterial lysates . The PCR procedure coupled with an enrichment culture incubated for 6 h detected as few as 1.6 S . flexneri organisms in pure culture . Treated sewage, ground, surface and drinking water samples collected from various sources were seeded with S . flexneri and incubated in GN broth for 6 h before detection by seminested PCR . A detection limit lower than 14 cfu/ml was achieved in some water samples . The results indicate that the described seminested PCR has the advantage of a rapid turnaround time and it fulfills the requirements of sensitivity and specificity for use in an environmental laboratory.

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