Microbes Infect, 1999 Jul, 1(8), 621 - 32 Perturbation and exploitation of host cell cytoskeleton by periodontal pathogens; Ellen RP; Some periodontal pathogens disrupt epithelial barriers and cellular adhesion to the extracellular matrix, which affects the cytoskeleton . Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans exploit the cytoskeleton during their uptake by epithelial cells . Treponema denticola perturbs actin and actin-regulating pathways in host cells . Cytoskeletal dysfunction due to pathogenic bacteria may impair physiologic remodeling and wound repair in the periodontium. Microbes Infect, 1999 Jul, 1(8), 609 - 14 Myristic acid analogs are inhibitors of Junin virus replication; Cordo SM et al.; The effects of two myristic acid analogs on Junin virus (JV) replication were investigated . The compounds chosen for the study were DL-2-hydroxymyristic acid (2OHM), an inhibitor of N-myristoyltransferase (NMT), which binds the enzyme and blocks protein myristoylation, and 13-oxamyristic acid (13OM), a competitive inhibitor of NMT which incorporates into the protein instead of myristic acid . Both types of analogs achieved dose-dependent inhibition of viral multiplication at concentrations not affecting cell viability . The 50% inhibitory concentration values determined by a virus-yield inhibition assay for different strains of JV, including a human pathogenic strain, and for the related arenavirus, Tacaribe, were in the range 1.6 to 20.1 microM, with 13OM as the most active compound . From time of addition and removal experiments, it can be concluded that both analogs inhibit a late stage in the JV replicative cycle, and their effect was partially reversible . The cytoplasmic and surface expression of JV glycoproteins was not affected in the presence of the compounds, as revealed by immunofluorescence staining, suggesting that JV glycoprotein myristoylation would not be essential for the intracellular transport of the envelope proteins, but it may have an important role in their interaction with the plasma membrane during virus budding. Curr Opin Biotechnol, 1999 Dec, 10(6), 571 - 8 Searching for drug targets in microbial genomes; Galperin MY et al.; Comparative analysis of the complete genome sequences of 10 bacterial pathogens available in the public databases offers the first insights into the drug discovery approaches of the near future . Genes that are conserved in different genomes often turn out to be essential, which makes them attractive targets for new broad-spectrum antibiotics . Subtractive genome analysis reveals the genes that are conserved in all or most of the pathogenic bacteria but not in eukaryotes; these are the most obvious candidates for drug targets . Species-specific genes, on the other hand, may offer the possibility to design drugs against a particular, narrow group of pathogens. Trop Anim Health Prod, 1999 Dec, 31(6), 347 - 61 Impact of mastitis control measures on milk production and mastitis indicators in smallholder dairy farms in Kiambu district, Kenya; Omore AO et al.; Bovine mastitis and mastitis control were investigated on smallholder farms in central Kenya . After an initial observational study, a clinical trial to assess the impact of three different mastitis control strategies--(1) improved udder hygiene, (2) treatment of subclinical cases, and (3) a combination of these--was conducted on 100 randomly selected farms with 332 lactating cows . Before the implementation of control measures, the milk yield was low (mean 6.5 kg/day; median 6 kg/day) and somatic cell counts (SCC) were high, with 80% and 43% of cows having milk with SCC greater than 250 x 10(3) cells/ml and 600 x 10(3) cells/ml, respectively . Infectious pathogens were also commonly isolated, with 63% of cows being positive for pathogenic bacteria . Neither intervention strategy alone had any effect on mastitis indicators or milk yield . In combination, the measures had some impact, lowering the prevalence of contagious pathogens by 18%, but this was not reflected in a significantly increased milk yield, lowered SCC or reduced incidence of clinical mastitis. Mol Cells, 1999 Oct 31, 9(5), 491 - 6 Cloning of a cysteine proteinase gene from Acanthamoeba culbertsoni; Yun HC et al.; Free living amoeba, including pathogenic Acanthamoeba culbertsoni, are widely distributed in soil and fresh water . It has been found that cysteine proteinases are more active in pathogenic strains of amoeba whereas serine proteinases are found in both pathogenic and nonpathogenic strains . Cysteine proteinases thus play important roles in the pathogenesis of several parasitic infections and have been proposed as targets for the structure-based strategy of drug design . As the first step toward applying this strategy to design inhibitors as antiparasitic agents for A . culbertsoni, we isolated and sequenced the full length clone of a cysteine proteinase gene from A . culbertsoni by performing reverse transcription-polymerase chain reaction (RT-PCR) with degenerate oligonucleotide primers derived from conserved cysteine proteinase sequences . The 5' and the 3' regions of the cysteine proteinase gene were amplified using the PCR protocol for the rapid amplification of cDNA ends (RACE) . It has an open reading frame of 1359 bp . The deduced amino acid sequence has the sequence homology with the cysteine proteinase genes of Paragonimus westermani metacercaria, Schistosoma mansoni, human cathepsin L and Fasciola hepatica, each by 45.3%, 45.9%, 57.9% and 50.8% respectively . Sequence analysis and alignment showed significant similarity to other eukaryotic cysteine proteinases, including the conservation of the cysteine, histidine, and asparagine residues that form the catalytic triad . A 1.5 kbp mRNA was detected on Northern blot analysis using full-length cysteine proteinase cDNA as a probe . The A . culbertsoni cysteine proteinase gene (AcCP2) was found to contain Ex3Rx3Wx2N at the proregion and also a proline/threonine-rich C-terminal extension . Therefore, it has cathepsin L-like characteristics . Phylogenetic analysis based on the amino acid sequences of cysteine proteinase indicated that AcCP2 was closely related with papaya, while it was remotely related with those of Schistosoma. Anaesthesia, 1999 Dec, 54(12), 1183 - 97 Ventilator-associated pneumonia . Diagnosis, pathogenesis and prevention; Young PJ et al.; Ventilator-associated pneumonia is common, difficult to diagnose, affects the most vulnerable of patients and carries a high mortality . During prolonged mechanical ventilation the oropharynx, sinuses, dentition and stomach of critically ill patients become colonised with pathogenic bacteria . Colonised secretions pool in the oropharynx and subglottic space . These secretions repeatedly gain access to the lower airways by leakage past the tracheal tube cuff . If host defence mechanisms are overwhelmed, multiplication occurs in the lower respiratory tract producing an inflammatory response in the bronchioles and alveoli . The inflammatory response is characterised by capillary congestion, leucocyte and macrophage infiltration and fibrinous exudation into the alveolar spaces . If this inflammatory response occurs more than 48 h after intubation, it is called ventilator-associated pneumonia . Prevention depends on reducing upper airway and gastrointestinal reservoirs of bacteria, reducing or abolishing aspiration of these bacteria past the tracheal tube cuff and enhancing bacterial clearance from the lower airways. J Med Primatol, 1999 Aug-Oct, 28(4-5), 181 - 9 Antigen-specific cytokine responses in vaccinated Macaca nemestrina; Mulvania T et al.; We describe a new surrogate assay for CD8 + T lymphocyte activity that has the capability of discriminating between cytotoxic T lymphocyte (CTL) activity and cytokine-mediated suppressive activity . We applied this approach to two groups of Macaca nemestrina vaccinated with a minimally pathogenic strain of human immunodeficiency virus type 2 {HIV-2 (HIV-2(KR))} as a model of an attenuated virus vaccine . Group 1 was then inoculated with a non-infectious stock of a pathogenic strain, HIV-2287 . Both groups 1 and 2 were subsequently challenged with an infectious stock of HIV-2287 . Five out of six group 1 animals were protected against CD4 decline, whereas three out of six animals in group 2 were protected . Analysis of CTL responses demonstrated strong activity against HIV-2(KR)-Gag in group 1 . It was determined that strong CTL responses correlate with antigen-specific T-helper (Th) type 1 responses . This antigen-specific cytokine assay has the potential to better elucidate the functional mechanisms of CD8 + T-cell-mediated protection than traditional methods to date. J Microbiol Immunol Infect, 1997 Feb, 30(1), 55 - 9 {Pathogenic strains of Escherichia coli in Taiwan}; Lee CL et al.; From July 1994 through June 1996, 28 strains of Escherichia coli were isolated from 1,260 patients with acute diarrhea . These strains were further differentiated with serotypes and virulence factors . Enterotoxigenic E . coli (ETEC), enteropathogenic E . coli (EPEC), enterohemorrhagic E . coli (EHEC), and enteroinvasive E . coli (EIEC) were accounted for 53.6 (15 of 28 strains), 28.6 (8 of 28), 10.7 (3 of 28) and 7.1% (2 of 28), respectively . Therefore, ETEC and EPEC are playing an important role in food-borne illness in Taiwan . Escherichia coli O157:H7, a new emerging pathogen of food-borne disease, has not been isolated in this study. Clin Infect Dis, 1999 Oct, 29(4), 888 - 911 The body louse as a vector of reemerging human diseases; Raoult D et al.; The body louse, Pediculus humanus humanus, is a strict human parasite, living and multiplying in clothing . Louse infestation is associated with cold weather and a lack of hygiene . Three pathogenic bacteria are transmitted by the body louse . Borrelia recurrentis is a spirochete, the agent of relapsing fever, recently cultured on axenic medium . Historically, massive outbreaks have occurred in Eurasia and Africa, but currently the disease is found only in Ethiopia and neighboring countries . Bartonella quintana is now recognized as an agent of bacillary angiomatosis bacteremia, trench fever, endocarditis, and chronic lymphadenopathy among the homeless . Rickettsia prowazekii is the agent of epidemic typhus . The most recent outbreak (and the largest since World War II) was observed in Burundi . A small outbreak was also reported in Russia in 1997 . Louse infestation appears to become more prevalent worldwide, associated with a decline in social and hygienic conditions provoked by civil unrest and economic instability. Pediatrics, 1999 Dec, 104(6), 1321 - 6 Tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 levels in febrile, young children with and without occult bacteremia; Strait RT et al.; OBJECTIVE: To determine the utility of plasma levels of tumor necrosis factor-alpha (TNF), interleukin 1 beta (IL-1), and interleukin 6 (IL-6) in the prediction of occult bacteremia in febrile, young children . STUDY DESIGN: Prospective, case-control study conducted in a large, urban, children's hospital emergency department . Eligibility criteria were: 0 to 36 months of age, febrile, nontoxic appearing, immunocompetent, no apparent bacterial source for fever on physical examination, and blood culture obtained . Additional blood, procured at the time of the blood culture, was analyzed by enzyme-linked immunosorbent assay for TNF, IL-1, and IL-6 . Children with positive blood cultures for pathogenic bacteria served as cases . Two age-matched controls for each case were selected from the children with negative cultures . RESULTS: Out of 1329 enrollees, 33 cases and 66 controls were evaluated . IL-6 levels were significantly higher for the cases than controls but with moderate overlap in their ranges . TNF and IL-1 levels were not significantly different between cases and controls . Height of fever, duration of fever, acute illness observation score, absolute band count, and white blood cell count were all much less predictive of bacteremia than either IL-6 or absolute neutrophil count (ANC) . The optimum IL-6 threshold value had a sensitivity of 88%, a specificity of 70%, a positive predictive value (PPV) of 7.0%, a negative predictive value (NPV) of 99.6%, and an odds ratio (OR) of 16.7 (95% confidence interval {CI}, 4.8-71.6) . The optimum ANC threshold value had a sensitivity of 82%, a specificity of 74%, a PPV of 7.5%, a NPV of 99.4%, and an OR of 12.8 (95% CI, 3.2-59.7) . The best predictor was a combination of IL-6 and ANC . It had a sensitivity of 100%, a specificity of 78%, a PPV of 10.4%, a NPV of 100%, and an OR which is undefined because of the 100% sensitivity (95% CI, 33.0-infinity) . For comparison, a WBC >15 x 10(9) cells/L had a sensitivity of 48%, a specificity of 79%, a PPV of 5.5%, a NPV of 98.3%, and an OR of 3 . 5 (95% CI, 1.1-10.7) . CONCLUSIONS: In febrile children 0 to 36 months of age, IL-6 levels may be helpful in the prediction of occult bacteremia, but TNF and IL-1 levels are not . IL-6 levels alone or notably when combined with an ANC were more predictive of occult bacteremia than traditional tests and clinical criteria . The wide range in the IL-6 values for cases and controls detracts from the precision of the findings . The lack of rapid processing and clinical availability of IL-6 assays hampers its present application . However, despite these drawbacks and given the poor ability of traditional clinical and laboratory criteria to predict occult bacteremia, these results suggest a possible future role for IL-6 in predicting occult bacteremia when rapid assays become available. Am J Rhinol, 1999 Sep-Oct, 13(5), 349 - 55 The relationship of nasal polyps, infection, and inflammation; Norlander T et al.; The role of infection as cause or effect in nasal polyps is debated . In experimentally induced sinusitis in rabbits, polyps are frequent . The initial polyp formation sequence involves multiple epithelial disruptions with proliferating granulation tissue . Regenerating epithelial branches spread into the underlying connective tissue, where intraepithelial microcavities give rise to a polyp body from the adjacent mucosa . Clinical as well as experimental studies indicate that nasal polyp formation and growth are activated and perpetuated by an integrated process of mucosal epithelium, matrix, and inflammatory cells, which in turn may be initiated by both infectious and noninfectious inflammation . The complexity of the pathophysiologic events in nasal polyposis is reinforced by the finding that epithelial desquamation, combined with infection or inflammation, will initiate polyp formation . Systemic glucocorticosteroids inhibit polyp formation as well as growth of pathogenic bacteria in the sinuses of rabbits with experimental infection . Therapeutic use of corticosteroids in polyp disease, combined with antibiotics or surgery, should be modified in relation to long-term progression, intensity variations, and predisposing conditions. Crit Care Med, 1999 Nov, 27(11), 2399 - 406 The effect of acidified enteral feeds on gastric colonization in critically ill patients: results of a multicenter randomized trial . Canadian Critical Care Trials Group; Heyland DK et al.; OBJECTIVE: To evaluate the effect of acidified enteral feeds on gastric colonization in critically ill patients compared with a standard feeding formula . DESIGN: Randomized, double-blind, multicenter trial . SETTING: Eight mixed intensive care units at tertiary care hospitals . PATIENTS: We recruited mechanically ventilated critically ill patients expected to remain ventilated for >48 hrs . We excluded patients with gastrointestinal bleeding, acidemia, and renal failure requiring dialysis . We enrolled 120 patients; 38% were female, age (mean +/- SD) was 57.6+/-19.3 yrs, and Acute Physiology and Chronic Health Evaluation II score (mean +/- SD) was 21.6+/-7.6 . INTERVENTIONS: Vital High Nitrogen (Abbott Laboratories, Ross Products Division, Columbus, OH) was used as the standard feeding formula for the control group (pH = 6.5) . Hydrochloric acid was added to Vital High Nitrogen to achieve a pH of 3.5 in the experimental group . MEASUREMENTS AND MAIN RESULTS: The main outcome measure was gastric colonization . Secondary outcomes included gastric pH, pneumonia, and mortality . The mean gastric pH in patients receiving acid feeds was lower (pH = 3.3) compared with controls (pH = 4.6; p<.05) . One patient (2%) on acid feeds was colonized in the stomach with pathogenic bacteria, compared with 20 patients (43%) in the control group (p<.001) . There was no difference in the incidence of pneumonia (6.1% in the acid feeds group vs . 15% in the control group; p = .19) . Overall, there were 15 deaths in the acid feeds group and seven in the control group (p = .10); four patients in the acid feeds group and three in the control group died during the study period (p not significant) . CONCLUSIONS: Acidified enteral feeds preserve gastric acidity and substantially reduce gastric colonization in critically ill patients . Larger studies are needed to examine its effect on ventilator-associated pneumonia and mortality. Int J Parasitol, 1999 Aug, 29(8), 1307 - 19 Pathogenicity of selected Toxoplasma gondii isolates in young pigs; Jungersen G et al.; The pathogenicity in 7-week-old pigs to five different Toxoplasma gondii strains of various host species origin was compared after i.v . inoculation of 10(4) tachyzoites . Additionally, one group of pigs was inoculated i.v . with 10(6) tachyzoites of the reference strain, SSI 119 . In response to the infection a significant effect of T . gondii tachyzoite inoculation dose as well as differences among strains could be observed in several parameters . The 10(6)-dose inoculated pigs showed variable degrees of clinical illness and recurrent episodes of fever 4-17 days p.i., while pigs of four of the 10(4) tachyzoite inoculated groups experienced a short-lived rise in body temperature from day 6-8 p.i . without any apparent illness or inappetence . Control pigs and pigs infected with the least pathogenic strain had normal body temperature throughout the experiment . In all inoculated pigs, T . gondii-specific IgM and IgG antibodies appeared from day 8-10 and 10-17 p.i., respectively . Serum levels of alkaline phosphatase and the acute phase protein haptoglobin were decreased or increased, respectively, in response to the infection . Differential leukocyte count on peripheral blood revealed a significant lymphocytopenia on day 6 p.i . equal to both CD4+ and CD8+ T-cells, but shifting towards a reduced ratio of CD4+/CD8+ T-cells from day 8-14 p.i . In the 10(6)-dose inoculated pigs a considerable increase in zymosan induced and spontaneous oxidative burst capacity of peripheral blood leukocytes was observed from 6 days p.i . compared with control pigs . Oxidative burst capacity was not examined for other pigs . In conclusion, several useful parameters to identify differences in T . gondii pathogenicity other than mortality were identified . Furthermore, even at low doses, significant differences between recently collected Danish T . gondii field isolates were demonstrated after i.v . inoculation in young pigs. Eur J Biochem, 1999 Dec, 266(2), 484 - 92 Conformations in solution of the fuscopeptins . Phytotoxic metabolites of Pseudomonas fuscovaginae; Bare S et al.; Fuscopeptins are phytotoxic amphiphilic lipodepsipeptides containing 19 amino acid residues . They are produced by the plant pathogenic bacterium Pseudomonas fuscovaginae in two forms, A and B, which differ only in the number of methylene groups in the fatty acid chain . Their covalent structure and biological properties have been reported previously . CD and NMR spectroscopy investigations in solution revealed the absence of identifiable elements of secondary and tertiary structure for these molecules . Fuscopeptin B appears to be completely unstructured in aqueous solution, and has a large molecular flexibility . A dramatic conformational change was observed upon addition of trifluoroethanol . This study reports the complete interpretation of the two-dimensional NMR spectra and the NOE results obtained for fuscopeptin B in water/trifluoroethanol solutions; the signals relative to the peptidic moiety are identical to those observed for fuscopeptin A . The results of this investigation were used to determine the solution structure of fuscopeptin B by computer simulations applying distance geometry and simulated annealing procedures . In water/trifluoroethanol solutions the peptidic region appears to have a partly helical structure . The lactonic ring assumes defined conformations very similar to those already reported for other lipodepsipeptides . The structure for fuscopeptin B in solution is also valid for fuscopeptin A because of the negligible structural difference between the two metabolites. J Virol, 1999 Dec, 73(12), 10346 - 58 Use of a gp120 binding assay to dissect the requirements and kinetics of human immunodeficiency virus fusion events; Doranz BJ et al.; Binding of the extracellular subunit of human immunodeficiency type 1 (HIV-1) envelope (Env) glycoprotein (gp120) to CD4 triggers the induction or exposure of a highly conserved coreceptor binding site in gp120 that helps mediate membrane fusion . Characterizing the structural features involved in gp120-coreceptor binding and the conditions under which binding occurs is important for understanding the fusion process, the evolution of pathogenic strains in vivo, the identification of novel anti-HIV compounds, and the development of HIV vaccines that utilize triggered structures of Env . Here we use the kinetics of interaction between CCR5 and gp120 to understand temporal and structural changes that occur during viral fusion . Using saturation binding and homologous competition analysis, we estimated the K(d) of interaction between CCR5 and gp120 from the macrophage tropic HIV-1 strain JRFL to be 4 nM . Unlike Env-mediated fusion, gp120 binding to CCR5 did not require divalent cations or elevated temperatures . Binding was not significantly affected by the pH of binding, G-protein coupling of CCR5, or partial gp120 deglycosylation . Oligomeric, uncleaved JRFL gp140 failed to bind CCR5 despite its ability to bind CD4 and monoclonal antibody 17b, suggesting that the uncleaved ectodomain of gp41 interferes with full exposure of the chemokine receptor binding site . Exposure of the chemokine receptor binding site on gp120 could be induced rapidly by CD4, but exposure of this site was lost upon CD4 dissociation from gp120, indicating that the conformational changes in gp120 induced by CD4 binding are fully reversible . The functional gp120-soluble CD4 complex was remarkably stable over time and temperature ranges, offering the possibility that complexes in which the highly conserved coreceptor binding site in gp120 is exposed can be used for vaccine development. Int J Syst Bacteriol, 1999 Oct, 49 Pt 4, 1577 - 89 Janthinobacterium agaricidamnosum sp . nov., a soft rot pathogen of Agaricus bisporus; Lincoln SP et al.; A novel bacterium has been found that causes a soft rot disease of Agaricus bisporus, the cultivated mushroom . It has been characterized using nutritional, physiological, chemical and molecular techniques . Based on these data, it was shown to have many characteristics in common with members of the genus Janthinobacterium . Despite similarities to the only described species within this genus, Janthinobacterium lividum, there were a number of differences between the mushroom pathogen isolated and this species . Despite the high degree of genotypic similarity between members of the genus Janthinobacterium and Herbaspirillum, as evidenced by DNA-RNA hybridization, and the high degree of 16S rDNA sequence similarity between members of the genera Janthinobacterium, Herbaspirillum, Oxalobacter and Duganella, as well as the generically misnamed Pseudomonas lemoignei, it was possible to show that members of the genus Janthinobacterium could be easily distinguished from these taxa . The data also indicated that the mushroom pathogenic strains represent a novel species within the genus Janthinobacterium for which the name Janthinobacterium agaricidamnosum sp . nov . is proposed . The type strain of this species has been deposited in the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany, as DSM 9628T and at the National Collection of Plant-pathogenic bacteria, UK, as NCPPB 3945T . To aid practical control of the disease, the effect of the relative humidity on symptom expression on Agaricus bisporus was determined. Anal Biochem, 1999 Nov 1, 275(1), 1 - 5 A method for extraction of high-quality and high-quantity genomic DNA generally applicable to pathogenic bacteria; Kalia A et al.; In this study, we report a modified procedure for extraction of high-quality genomic DNA that is rapid, simple, biologically nonhazardous, and generally applicable to pathogenic bacteria . Bacterial cells were pretreated with 70% ethanol prior to enzymatic digestion with lysozyme . Exposure of bacterial cells to 70% ethanol sterilized the cultures, making the process biologically safe and increased the susceptibility of the cells to lysozyme-induced lysis . Consistently high yields of genomic DNA (mean average yield, 0.5-2.5 mg/ml) were obtained from 465 isolates representing over 30 clinically important bacterial species . Genomic DNA obtained was determined to be suitable for further analysis, including bacterial fingerprinting techniques like restriction endonuclease analysis, Southern hybridization, and repetitive PCR . Availability of a generally applicable procedure for extraction of high-quality and high-quantity genomic DNA would be immensely beneficial for laboratories engaged in molecular surveillance of nosocomial and community-based outbreaks . Acta Crystallogr D Biol Crystallogr, 1999 Nov, 55(11), 1925 - 7 Crystallization and preliminary x-ray structure determination of Lupinus luteus PR10 protein; Biesiadka J et al.; The pathogenesis-related protein of the PR10 class from Lupinus luteus (yellow lupin), LlPR10.1A, is constitutively expressed in roots . It is also accumulated in leaves treated with a suspension of pathogenic bacteria as a response to stress . Recombinant yellow-lupin LlPR10.1A protein has been overexpressed in Escherichia coli as a fusion product with maltose-binding protein . LlPR10.1A crystallizes in the orthorhombic P2(1)2(1)2(1) space group and the crystals diffract to 2.45 A resolution . The structure has been solved by molecular replacement, using the structure of a birch-pollen allergen protein as a model. Microbiol Immunol, 1999, 43(7), 717 - 21 Phenotypic and genotypic homogeneity of the strains of Rickettsia japonica isolated from patients with Oriental spotted fever; Uchiyama T; Nine pathogenic strains of Rickettsia japonica isolated from patients with Oriental spotted fever were compared phenotypically and genotypically . Constitution and antigenicity of the proteins demonstrated to be the same among strains . Polymerase chain reaction (PCR) amplification of the two major outer membrane protein genes (ompA and ompB) and an intracellular spotted fever group-common antigen protein gene (rps120) produced the same sizes of products for all strains . Restriction fragment length polymorphism of the PCR products showed the same pattern among strains with each endonuclease . Thus, these strains belong to a single type, the same as the type strain YH (=ATCC VR-1363). Scand J Infect Dis, 1999, 31(4), 383 - 5 Free-living amoebae protecting Legionella in water: the tip of an iceberg? Winiecka-Krusnell J, Linder E. Bacteria are a main food source for free-living amoebae inhabiting aquatic systems . Some bacteria however, have the ability to prevent intracellular destruction and can survive and grow in amoebic cells as endosymbionts . Free-living amoebae are well adapted to their hostile environmental conditions and are resistant to both desiccation, elevated temperatures and various disinfectants . For their endosymbionts, amoebae represent perfect vectors, providing both protection against adverse environmental conditions and transportation . There is increasing interest in the potential role of free-living amoebae as reservoirs and vectors of pathogenic bacteria . The best known of such pathogenic bacteria is Legionella, and several studies provide evidence for the importance of the amoeba-bacterium relationship in the biology and epidemiology of pneumonia caused by this pathogen . Although the relative importance of endosymbiosis of this kind is unknown when it comes to other human bacterial infections and the exact role of amoebic hosts in bacterial survival, multiplication and transmission in the environment is still poorly understood, naming free-living amoebae the "Trojan horses" of the microbial world is appropriate. J Biol Chem, 1999 Oct 22, 274(43), 30697 - 706 The COOH terminus of aminoglycoside phosphotransferase (3')-IIIa is critical for antibiotic recognition and resistance; Thompson PR et al.; The aminoglycoside phosphotransferases (APHs) are widely distributed among pathogenic bacteria and are employed to covalently modify, and thereby detoxify, the clinically relevant aminoglycoside antibiotics . The crystal structure for one of these aminoglycoside kinases, APH(3')-IIIa, has been determined in complex with ADP and analysis of the electrostatic surface potential indicates that there is a large anionic depression present adjacent to the terminal phosphate group of the nucleotide . This region also includes a conserved COOH-terminal alpha-helix that contains the COOH-terminal residue Phe(264) . We report here mutagenesis and computer modeling studies aimed at examining the mode of aminoglycoside binding to APH(3')-IIIa . Specifically, seven site mutants were studied, five from the COOH-terminal helix (Asp(261), Glu(262), and Phe(264)), and two additional residues that line the wall of the anionic depression (Tyr(55) and Arg(211)) . Using a molecular modeling approach, six ternary complexes of APH(3')-IIIa.ATP with the antibiotics, kanamycin, amikacin, butirosin, and ribostamycin were independently constructed and these agree well with the mutagenesis data . The results obtained show that the COOH-terminal carboxylate of Phe(264) is critical for proper function of the enzyme . Furthermore, these studies demonstrate that there exists multiple binding modes for the aminoglycosides, which provides a molecular basis for the broad substrate- and regiospecificity observed for this enzyme. Clin Chest Med, 1999 Sep, 20(3), 653 - 70 Epidemiology and risk factors for nosocomial pneumonia . Emphasis on prevention; Kollef MH; VAP is a complex nosocomial infection, the disease expression and resulting patient outcome of which is dependent on host factors, the causative organism, the timing and adequacy of treatment, and the presence of intrinsic or inducible antibiotic resistance . Significant improvements have been achieved in our ability to reduce the occurrence of VAP in the hospital setting . Clinicians caring for mechanically ventilated patients should strive to develop focused programs for the prevention of VAP, other nosocomial infections, and the occurrence of antibiotic-resistant infections at their institutions . The benefits of such programs are well demonstrated . The components of a PDSA (Plan-Do-Study-Act) model that can be simply employed to develop a VAP prevention program are as follows: Stages Plan: 1 . Identify potentially modifiable risk factors for VAP at the institutional level . 2 . Develop a strategy to modify or prevent the occurrence of these risk factors . {figure: see text} Do: 1 . Carry out the planned intervention strategy . 2 . Identify problems in the implementation of the designed intervention . 3 . Update the intervention with solutions for the identified problems . 4 . Collect basic data (e.g., VAP rates, severity of illness) . Study: 1 . Analyze data . 2 . Summarize the results . Act: 1 . Determine the overall success or failure of the intervention . 2 . Identify potential modifications to improve the intervention strategy . 3 . Prepare for next PDSA cycle . Inherent in the development and application of such programs is the concept that they are continuous processes striving to improve clinical performance over time (Fig . 3) . At any given institution, the most likely approach to the prevention of NP and VAP will be a multifaceted one, employing interventions aimed at reducing the occurrence of aerodigestive tract colonization with pathogenic bacteria and aspiration . To be successful, such quality improvement programs must be embraced at the institutional level . Only in this way can hospitals hope to successfully reduce their rates of VAP and sustain or improve upon those efforts over time. J Med Assoc Thai, 1999 Jul, 82(7), 643 - 7 Prevalence of disseminated Mycobacterium avium complex infection in Thai AIDS patients; Chuchottaworn C et al.; Infections caused by nontuberculous mycobacteria (NTM), although rare in immuno-competent individuals, can potentially produce problems in immunocompromised patients such as those with acquired immunodeficiency syndrome (AIDS) . In this study, hemocultures for mycobacteria using radiometric BACTEC 13A media were taken from 334 patients with known human immunodeficiency virus infection admitted to four referral hospitals with fever of unknown site of infection and negative blood cultures for pathogenic bacteria . The mycobacterial hemocultures were positive for Mycobacterium avium complex (MAC) in 58 patients (17.4%) and positive for Mycobacterium tuberculosis in 34 patients (10.2%) . The results of this study have proved that MAC infection, indeed, exists among Thai AIDS patients . The prevalence of MAC infection in Thailand is very high and comparable to that in the western countries . Physicians taking care of AIDS patients in Thailand should be aware of potential MAC infection, particularly in advanced cases . Considering the high prevalence of infection, primary prophylaxis against MAC infection in advanced AIDS patients is recommended. J Antimicrob Chemother, 1999 Sep, 44(3), 337 - 41 Faropenem enhances superoxide anion production by human neutrophils in vitro; Sato K et al.; Neutrophils are important cellular components in the defence against infections and many studies in vitro have shown that some antibiotics affect neutrophil function . We examined the effect of faropenem, a new oral penem antibiotic on neutrophil killing function by determining the generation of superoxide anion in vitro . The production of superoxide anion was measured by chemiluminescence amplified by a Cypridina luciferin analogue in the presence of N-formyl-Met-Leu-Phe (fMLP) . Faropenem significantly enhanced chemiluminescence in a dose-dependent manner . The effect of faropenem was maximal at 5 min of incubation time and continued for at least 30 min . The effect of faropenem was also observed when neutrophils were stimulated by a calcium ionophore (ionomycin), while the effect of faropenem did not change in the presence of 12-O-tetra-decanoylphorbolmyristate acetate . Cytosol Ca2+ concentration ({Ca2+}i) monitored with Fura-2 increased in response to fMLP, however, faropenem did not influence the response of {Ca2+}i to fMLP . Our results suggest that faropenem enhanced the generation of superoxide anion by neutrophils, probably at the site where cytosol Ca2+ regulates NADPH oxidase . Faropenem might be potentially advantageous in the treatment of infections because a synergic interaction of antibodies and cytocidal neutrophils is necessary for the early eradication of the pathogenic bacteria. Nat Biotechnol, 1999 Oct, 17(10), 1021 - 4 Engineered detoxification confers resistance against a pathogenic bacterium; Zhang L et al.; We generated transgenic sugarcane plants that express an albicidin detoxifying gene (albD), which was cloned from a bacterium that provides biocontrol against leaf scald disease . Plants with albicidin detoxification capacity equivalent to 1-10 ng of AlbD enzyme per mg of leaf protein did not develop chlorotic disease symptoms in inoculated leaves, whereas all untransformed control plants developed severe symptoms . Transgenic lines with high AlbD activity in young stems were also protected against systemic multiplication of the pathogen, which is the precursor to economic disease . We have shown that genetic modification to express a toxin-resistance gene can confer resistance to both disease symptoms and multiplication of a toxigenic pathogen in its host. Infect Control Hosp Epidemiol, 1999 Sep, 20(9), 626 - 8 Bacterial contamination of hospital physicians' stethoscopes; Bernard L et al.; Because stethoscopes might be potential vectors of nosocomial infections, this study, conducted in a 450-bed general hospital, was devised to evaluate the bacterial contamination of stethoscopes; bacterial survival on stethoscope membranes; the kinetics of the bacterial load on stethoscope membranes during clinical use; and the efficacy of 70% alcohol or liquid soap for membrane disinfection . Among the 355 stethoscopes tested, 234 carried > or =2 different bacterial species; 31 carried potentially pathogenic bacteria . Although some bacteria deposited onto membranes could survive 6 to 18 hours, none survived after disinfection. Avian Dis, 1999 Jul-Sep, 43(3), 414 - 23 Pathologic study of specific-pathogen-free chicks and hens inoculated with adenovirus isolated from hydropericardium syndrome; Nakamura K et al.; The mortality and pathology caused by serotype 4 adenovirus, isolated from chickens with hydropericardium syndrome (HPS) in Japan, was investigated in specific-pathogen-free (SPF) chickens . One-day-old to 15-mo-old SPF chickens were inoculated intramuscularly, orally, and intranasally with liver homogenates from HPS chickens or isolated serotype 4 adenovirus . There were no clinical signs before death . The mortality rate in all groups of 1-day-old chicks was 100%, irrespective of the inoculum or inoculation route . Four-week-old chickens inoculated with liver homogenate also had a 100% mortality rate . Five-week-old chickens inoculated with cell culture of HPS adenovirus had a 40% mortality rate . The mortality rates of 7-mo-old hens inoculated with liver homogenates intramuscularly and orally were 75% and 25%, respectively . In 15-mo-old hens inoculated with liver homogenates intramuscularly, the mortality rate was 70% . Gross lesions were hydropericardium and swelling and congestion of the liver with occasional petechial hemorrhages . Histologically, the liver had diffuse or multifocal hepatic necrosis and hemorrhage with intranuclear inclusion bodies noted within hepatocytes . In the spleen, macrophages containing erythrocytes and yellow pigment were prominent in the red pulp . In the lung, a moderate diffuse macrophage infiltration was noted throughout the lung parenchyma, and these macrophages contained yellow pigment . In the pancreas of the chicks inoculated at 1 day old, there was multifocal necrosis of glands with intranuclear inclusion bodies . Intranuclear inclusion bodies were seen also in the gizzard, proventriculus, duodenum, cecum, kidney, and lung of the chicks inoculated at 1 day old . Immunohistochemically, the intranuclear inclusion bodies of various organs showed positive reactions against group I avian adenovirus . Adenovirus was recovered from the liver of chickens with HPS . This study indicates that HPS adenovirus is able to reproduce HPS lesions and mortality in SPF chicks and even adult chickens and that it is a highly pathogenic strain. Indian J Exp Biol, 1999 May, 37(5), 429 - 33 Role of bio-metal Fe(III) in anticancer behaviour of tamoxifen; Shukla J et al.; Physicochemical, microbial and pharmacological studies on Fe (III)--Tamoxifen complex have been carried out in solid and aqueous phases . On the basis of elemental analysis, polarographic studies, amperometric titrations and IR spectral studies the probable formula for the complex has been worked out to be 1:1, Fe(III)--Tamoxifen . A tentative structure has been suggested to the complex . The metal ligand interaction has been studied using polarographic method at 27 degrees +/- 1 degree C and at ionic strength of mu = 1.0 (KCl) . Microbial studies on the complex was carried out against various pathogenic bacteria and fungi using Raper's method . Mouse sarcoma cell line 180 and Balb/C mice were used for the anticancer screening of solid complex, in vitro and in vivo, respectively . The results of microbial and pharmacological studies with the M:Drug complex revealed that the complex is more potent as compared to the pure drug as regards to its anticancer activity . As such Fe (III) Tamoxifen complex may be recommended to the therapeutic experts for its possible use as more potent anticancer drug. Dtsch Tierarztl Wochenschr, 1999 Aug, 106(8), 319 - 25 {Seafood transmitted diseases}; Feldhusen F; This paper reviews seafood related bacterial, viral and parasitological hazards for consumers worldwide . Seafood from Europe is generally regarded as safe . Food safety risks associated with aquaculture products results from contamination with biological agents, which are greater in freshwater and coastal ecosystems than in open seas . Due to the consumption conditions and the intensive investigations of imported products with contamination of pathogenic bacteria there are little seafood risks in Europe . Viral infections are associated with consumption of raw or recontaminated shellfish . There has been speculation that more than 50% of the outbreaks of unknown aethiology are due to viruses . Foodborne parasitic hazards are associated with the consumption of raw (sushi) or insufficiently heated, marinated and salted seafood. J Clin Microbiol, 1999 Oct, 37(10), 3159 - 66 Molecular analysis of riboflavin synthesis genes in Bartonella henselae and use of the ribC gene for differentiation of Bartonella species by PCR; Bereswill S et al.; The biosynthesis pathway for riboflavin (vitamin B(2)), the precursor of the essential cofactors flavin mononucleotide and flavin adenine dinucleotide, is present in bacteria and plants but is absent in vertebrates . Due to their conservation in bacterial species and their absence in humans, the riboflavin synthesis genes should be well suited either for detection of bacterial DNA in human specimens or for the differentiation of pathogenic bacteria by molecular techniques . A DNA fragment carrying the genes ribD, ribC, and ribE, which encode homologues of riboflavin deaminase (RibD) and subunits of riboflavin synthetase (RibC and RibE), respectively, was isolated from a plasmid-based DNA library of the human pathogen Bartonella henselae by complementation of a ribC mutation in Escherichia coli . Sequence analysis of the ribC gene region in strains of B . henselae, which were previously shown to be genetically different, revealed that the ribC gene is highly conserved at the species level . PCR amplification with primers derived from the ribC locus of B . henselae was used to isolate the corresponding DNA regions in B . bacilliformis, B . clarridgeiae, and B . quintana . Sequence analysis indicated that the riboflavin synthesis genes are conserved and show the same operon-like genetic organization in all four Bartonella species . Primer oligonucleotides designed on the basis of localized differences within the ribC DNA region were successfully used to develop species-specific PCR assays for the differentiation of B . henselae, B . clarridgeiae, B . quintana, and B . bacilliformis . The results obtained indicate that the riboflavin synthesis genes are excellent targets for PCR-directed differentiation of these emerging pathogens . The PCR assays developed should increase our diagnostic potential to differentiate Bartonella species, especially B . henselae and the newly recognized species B . clarridgeiae. J Biotechnol, 1999 Aug 20, 73(2-3), 251 - 60 Pigs aerogenously immunized with genetically inactivated (ghosts) or irradiated Actinobacillus pleuropneumoniae are protected against a homologous aerosol challenge despite differing in pulmonary cellular and antibody responses; Katinger A et al.; Aerosol immunization is a safe way to induce complete protection against pleuropneumonia in pigs caused by the lung pathogenic bacterium Actinobacillus pleuropneumoniae . In order to determine the local immune responses of vaccinees in concomitant with protection, lung lining fluid before and 3 weeks after immunization from pigs immunized three times with aerosols of either genetically inactivated ghosts which represent whole cell envelope preparations, or irradiated bacteria were examined following an homologous aerosol challenge . Specific antibody isotypes in the bronchoalveolar lavage were assayed by whole cell ELISAs . Total and relative numbers of cells including lymphocyte subsets were determined . In both vaccinated groups a net influx of plasma cells and lymphocytes, as well as a significant increase of specific IgG occurred . Concurrently, the CD4+/CD8+ ratio was found to increase after aerosol immunization . The lymphocyte subsets of IgG+ and IgA+ cells were found significantly higher in the group immunized with irradiated bacteria when compared to pigs immunized with bacterial ghosts . The latter group showed a significant increase of IgA, IgM, and a net influx of lymphoid blasts and granulocytes in the bronchoalveolar lining fluid . Although differences between the local immune responses of both immunized groups occurred, a significant increase of specific IgG and a net influx of plasma cells and lymphocytes were found to be associated with complete protection against a homologous aerosol challenge infection. FEMS Microbiol Lett, 1999 Oct 1, 179(1), 73 - 8 Apoptosis of murine peritoneal macrophages induced by an avian pathogenic strain of Escherichia coli; Rodrigues VS et al.; The mechanisms used by avian strains of Escherichia coli to invade the respiratory epithelia, leading to septicemia in poultry, are not well-established . In this work, we show that resident murine peritoneal macrophages infected in vitro with an avian strain of E . coli underwent apoptosis 4 h after infection (55.6% of apoptosis in infected cells versus 3.5% in non-infected cells) . Heat-inactivated bacteria did not induce apoptosis and the inhibition of phagocytosis by pretreatment of cells with cytochalasin D reduced the number of apoptotic cells from 55.6 to 13.9% (P<0.05), showing that the bacteria must be intracellularly located and viable to induce apoptosis . Therefore, these data suggest that induction of macrophage apoptosis may be a pathogenic mechanism employed by avian E . coli to circumvent the host defences and invade the respiratory epithelia. Acta Anaesthesiol Scand, 1999 Aug, 43(7), 760 - 3 Halothane decreases bacterial adherence in vitro; Batai I et al.; BACKGROUND: Adherence of pathogenic bacteria to host epithelial cells is thought to be the initial step in infection, while the presence of the commensal flora is an important host defence mechanism . Anything altering bacterial adherence to human epithelial cells may contribute to bacterial infections . The impact of anaesthesia on this first step to infection is not known . In this study the effect of halothane on bacterial adherence was investigated . METHODS: Human epithelial cells (HEp-2) and two strains of Escherichia coli were exposed to halothane 2% for 2 h . Then HEp-2 cells were coincubated with bacteria for 3 h . Bacteria attached to the epithelial cells were evaluated by light microscopy . RESULTS: Compared to the control, bacterial adherence was reduced by 37% to 56% with the different strains when HEp-2 cells were exposed to halothane . No significant difference was found when only bacteria were treated with halothane . CONCLUSION: Our results show that halothane reduces bacterial adherence to human epithelial cells in vitro . Reduced number or function of epithelial cell surface receptors may be responsible for the reduced adherence as no changes were observed when only the bacteria were exposed to halothane. Am J Vet Res, 1999 Aug, 60(8), 937 - 41 Response of embryonic chicken lymphocytes to in ovo exposure to lymphotropic viruses; St Hill CA et al.; OBJECTIVE: To examine effects of virus exposure on embryonic lymphoid organ structure, apoptosis, and lymphoid cell subpopulations . ANIMALS: Eggs of specific pathogen free (SPF) White Leghorn chickens at embryonation day (ED) 17 . PROCEDURES: Eggs were inoculated with 2,000 plaque-forming units (PFU) of serotype 1 herpesvirus (Marek's disease virus {MDV 1}), 2,000 PFU of herpesvirus of turkeys (MDV 3), or 1,000 embryo infectious doses (EID50) of infectious bursal disease virus (IBDV) . On post-inoculation days (PID) 3 and 5, lymphoid organ to body weight ratios were determined, and bursa of Fabricius, thymus, and spleen were evaluated for lesions and apoptosis . Proportions of lymphoid cell subpopulations of PID-3 chicken embryos and 7- to 10-day-old chicks were quantitated by flow cytometry . RESULTS: Lymphoid organ weights were similar in virus-free, MDV1, and IBDV groups . Embryos inoculated with 2,000 PFU MDV 3/egg had lower bursal weights than virus-free controls . In a repeated trial, MDV 3 (1,000 PFU to 4,000 PFU) did not reduce bursal weights among groups . Histologic changes were seen in bursae after MDV 1 and IBDV inoculation . Apoptosis was greater in bursae of MDV 1-infected embryos than controls . Lymphoid cell subpopulations were similar among all groups with the exception of CD8+ and IgM+ cells in spleens of IBDV-infected 10-day-old chicks . CONCLUSIONS AND CLINICAL RELEVANCE: Infection with pathogenic strains of MDV 1 and IBDV did not alter lymphocyte subpopulations in embryos or cause complete destruction of lymphoid organs . Changes in lymphoid cell subpopulations exposed as embryos to IBDV were seen only after hatching. J Med Microbiol, 1999 Aug, 48(8), 741 - 9 Molecular fingerprinting of Porphyromonas gingivalis by PCR of repetitive extragenic palindromic (REP) sequences and comparison with other fingerprinting methods; Teanpaisan R et al.; Knowledge of the genetic structure of populations of potentially pathogenic bacteria is important in understanding the epidemiology of diseases . Porphyromonas gingivalis is thought to be an important aetiological agent in periodontal diseases and several methods have been used for typing strains of this species . Here, PCR with primers to repetitive extragenic palindromic sequences (REP-PCR) was compared with three other widely used molecular fingerprinting techniques -- restriction endonuclease analysis (REA), ribotyping and PCR with arbitrary primers (AP-PCR) -- to type P . gingivalis isolates from healthy and diseased periodontal sites . The data obtained with all four methods were in broad agreement and, with one exception, each subject harboured a single unique genotype of P . gingivalis . REP-PCR of P . gingivalis resulted in the production of 5-10 amplicons, which gave unique electrophoretic patterns in each individual (10 REP-PCR types in 10 patients) and similar results were obtained with AP-PCR . Two isolates from one subject appeared identical by REP-PCR and AP-PCR, but could be differentiated by ribotyping, although there was only minor polymorphism . Thus, ribotyping and REA were the most discriminating methods; however, these are time-consuming and expensive relative to the PCR-based techniques . REP-PCR has the advantage that the same pair of primers is used for all species, whereas AP-PCR needs to be optimised by screening a range of primers . These results show that REP-PCR is a useful and rapid technique for typing P . gingivalis. Rinsho Byori, 1999 Jul, 47(7), 669 - 75 {Invasive amebiasis at an institution for the mentally retarded in Hyogo Prefecture}; Ono K et al.; An outbreak of amebiasis caused by Entamoeba histolytica occurred at an institution for mentally retarded persons in Hyogo Prefecture . Twelve out of a total of 49 admitted persons exhibited E . histolytica cysts in their stool, and 13 including persons in whom no cysts had been detected showed positive serological reactions for E . histolytica infection . However, neither the cyst nor the antibody against the organism was detected in the staff members of the institution . Indirect fluorescence antibody test and sandwich enzyme-linked immunosorbent assay with a monoclonal antibody specific for pathogenic strains of E . histolytica revealed that all trophozoite strains grown from cysts in stool samples from five patients were pathogenic . Epidemiological analysis strongly suggested that a patient in the institution had been infected with an organism from a patient outside the institution, and that infection may have spread among the admitted persons due to abnormal behavior . Administration of metronidazole resulted in effective elimination of the cysts from the stool of the cyst-carriers. Biochem Biophys Res Commun, 1999 Aug 11, 261(3), 598 - 602 Rapid and efficient inactivation of IL-6 gingipains, lysine- and arginine-specific proteinases from Porphyromonas gingivalis; Banbula A et al.; Deregulation of the cytokine network is an important adaptation of pathogenic bacteria to modulate and evade a host immune response . Here we describe that IL-6 is rapidly and efficiently cleaved and inactivated by the arginine- and lysine-specific proteinases from Porphyromonas gingivalis, referred to as RGP-A, RGP-B, and KGP . One of the primary cleavage sites for RGPs has been mapped between R18 and Q19 within the N-terminal region of the IL-6 polypeptide chain; however, both KGP and RGPs cleave IL-6 within the C-terminal region of the polypeptide chain . After these initial proteolytic cleavages, IL-6 is further degraded by each of the enzymes tested . Although KGP is the most potent IL-6-degrading proteinase, the initial C-terminal cleavage of IL-6 mediated by all gingipains is already sufficient to inactivate this cytokine . Our data are consistent with the observation that in periodontitis the IL-6 concentration is lowest in the gingival tissue adjacent to bacterial plaque, whereas significantly elevated concentrations of this cytokine are detected around the infected area . Degradation of IL-6 by gingipains may, therefore, represent an additional mechanism which influences the balance between pro- and anti-inflammatory reactions at distal versus proximal sites from the periodontal plaque . J Periodontol, 1999 Jul, 70(7), 793 - 802 Role of oral bacteria in respiratory infection; Scannapieco FA; An association between oral conditions such as periodontal disease and several respiratory conditions has been noted . For example, recent evidence has suggested a central role for the oral cavity in the process of respiratory infection . Oral periodontopathic bacteria can be aspirated into the lung to cause aspiration pneumonia . The teeth may also serve as a reservoir for respiratory pathogen colonization and subsequent nosocomial pneumonia . Typical respiratory pathogens have been shown to colonize the dental plaque of hospitalized intensive care and nursing home patients . Once established in the mouth, these pathogens may be aspirated into the lung to cause infection . Other epidemiologic studies have noted a relationship between poor oral hygiene or periodontal bone loss and chronic obstructive pulmonary disease . Several mechanisms are proposed to explain the potential role of oral bacteria in the pathogenesis of respiratory infection: 1 . aspiration of oral pathogens (such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, etc.) into the lung to cause infection; 2 . periodontal disease-associated enzymes in saliva may modify mucosal surfaces to promote adhesion and colonization by respiratory pathogens, which are then aspirated into the lung; 3 . periodontal disease-associated enzymes may destroy salivary pellicles on pathogenic bacteria to hinder their clearance from the mucosal surface; and 4 . cytokines originating from periodontal tissues may alter respiratory epithelium to promote infection by respiratory pathogens. Mol Ecol, 1999 Jun, 8(6), 1055 - 61 Natural selection promotes divergence of transferrin among salmonid species; Ford MJ et al.; Transferrin is an iron-binding protein that plays an important role in iron metabolism and resistance to bacterial infection in a variety of organisms . A comparison of transferrin coding sequences from four salmonid species shows that the rate of evolution at nonsynonymous sites is significantly higher than the rate at synonymous sites, suggesting that positive natural selection for new alleles has played an important role in the evolution of transferrin in some salmon species . We hypothesize that the selective agent driving rapid divergence is interactions between host transferrin and the iron-scavenging proteins of pathogenic bacteria. Parasitol Res, 1999 Aug, 85(8-9), 692 - 9 Iron enhancement of experimental infection of mice by Tritrichomonas foetus; Kulda J et al.; The ability of a microbial invader to acquire iron from its vertebrate host has been recognized as an important virulence mechanism in some pathogenic bacteria . We examined the involvement of similar mechanisms in an experimental infection of mice by a protozoan pathogen of cattle, Tritrichomonas foetus . In a series of experiments, outbred ICR mice were inoculated intraperitoneally with two strains of T . foetus, the moderately virulent KV-1 (approximately 5% mortality rate) and the highly virulent LUB-1MIP (approximately 80% mortality rate) . Treatment of mice with ferric ammonium citrate (FeAC) (100 mg/kg per day intraperitoneally) increased the mortality rate caused by the KV-1 infection up to the level determined for the highly virulent strain . The treatment effect was dose dependent and required early administration of FeAC after inoculation of parasites and its continued supply for at least 3 subsequent days . Daily sampling of peritoneal exudate showed that the infection-enhancing effect of iron overload was associated with a stimulation of parasite multiplication, which in the case of KV-1 infection was strongly suppressed in untreated mice . Consistent with these findings, the strain of lower virulence (KV-1) showed considerably lower efficiency accumulating radiolabeled iron from transferrin and a low-molecular source {Fe(III)nitrilotriacetic acid} in vitro . The results indicate an involvement of iron uptake mechanisms by the parasite as a virulence factor in T . foetus infection. Structure Fold Des, 1999 Jul 15, 7(7), 745 - 56 Structure of L-aspartate oxidase: implications for the succinate dehydrogenase/fumarate reductase oxidoreductase family; Mattevi A et al.; BACKGROUND: Given the vital role of NAD+ in cell metabolism, the enzymes involved in bacterial de novo NAD+ biosynthesis are possible targets for drug design against pathogenic bacteria . The first reaction in the pathway is catalysed by L-aspartate oxidase (LASPO), a flavoenzyme that converts aspartate to iminoaspartate using either molecular oxygen or fumarate as electron acceptors . LASPO has considerable sequence homology with the flavoprotein subunits of succinate dehydrogenase (SDH) and fumarate reductase (FRD) . RESULTS: The crystal structure of the apoform of LASPO from Escherichia coli has been determined to 2.2 A resolution . The enzyme shows a novel fold for an FAD-dependent protein, comprising a three-domain structure: an FAD-binding domain with the dinucleotide-binding fold, a C-terminal three-helical bundle domain, and an alpha + beta capping domain, which is topologically similar to the small subunit of spinach ribulose-1,5-bisphosphate carboxylase/oxygenase . The interface between the FAD-binding and capping domains defines a cleft in which the active site is located . CONCLUSIONS: A number of strictly conserved residues present in all three domains indicate that LASPO, SDH and FRD share the same overall folding topology . Many of these conserved residues are in the FAD-binding site and active centre, suggesting a similar catalytic mechanism . Thus, LASPO, SDH and FRD form a class of functionally and structurally related oxidoreductases that are all able to reduce fumarate and to oxidise a dicarboxylate substrate. Virology, 1999 Aug 1, 260(2), 295 - 307 Derivation and biological characterization of a molecular clone of SHIV(KU-2) that causes AIDS, neurological disease, and renal disease in rhesus macaques; Liu ZQ et al.; Previously, we described the derivation of a pathogenic strain of simian-human immunodeficiency virus (SHIV(KU-2)) consisting of the tat, rev, vpu, and env genes of HIV-1 (strain HXB2) in a genetic background of SIV(mac)239 that causes AIDS and productive infection of the CNS in rhesus macaques (Macca mulatta) (Raghavan et al., 1997, Brain Pathol . 7, 851-861) . We report here on the characterization of a molecular clone of SHIV(KU-2), designated SHIV(KU-2MC4), that caused CD4(+) T cell loss as well as neurological and renal disease in macaques . DNA sequence analysis of selected SIV regions of SHIV(KU-2MC4) revealed 10 nucleotide changes in the LTR, whereas Gag, Vif, Vpr, Vpx, and Nef had 1, 1, 1, 2, and 13 predicted amino acid substitutions, respectively, compared to SIV(mac)239 . DNA sequence analysis of HIV-1 derived regions of SHIV(KU-2MC4) revealed 2, 1, 2, and 18 predicted amino acid substitutions in the Tat, Rev, Vpu, and Env proteins, respectively, when compared to SHIV-4 . Unlike the parental SHIV-4, which is not tropic for macrophages, SHIV(KU-2MC4) replicated efficiently in macrophage cultures as determined by p27 assays . However, despite the numerous changes in the Env protein and newly acquired tropism for macrophages, SHIV(KU-2MC4), like the parental SHIV-4, used CXCR4 exclusively as its coreceptor for entry into susceptible cells . Inoculation of SHIV(KU-2MC4) into two rhesus macaques resulted in severe infection in which the numbers of circulating CD4(+) T cells in the blood declined rapidly by 2 weeks postinoculation and virus producing cells in the peripheral blood mononuclear cells were identified throughout the course of infection . At the time of euthanasia (20 and 22 weeks), both macaques had lost a significant amount of weight and had no circulating CD4(+) T cells . In addition, one macaque developed intension tremors and uncoordinated movements . Virological examination of tissues at necropsy revealed active virus replication in both lymphoid and nonlymphoid tissues such as the lung and brain . Histological examination revealed that the induced immunodeficiency was associated with lymphoid depletion of the lymph nodes and spleen, opportunistic infections, lentiviral encephalitis, and severe glomerulosclerosis of the kidney . This molecular clone will serve as the basis for analyzing the molecular determinants through which SHIV(KU-2) causes severe CD4(+) T cell loss, neurological disease, and SHIV nephropathy in rhesus macaques . Vaccine, 1999 May 4, 17(18), 2265 - 74 Baculovirus-derived hemagglutinin vaccines protect against lethal influenza infections by avian H5 and H7 subtypes; Crawford J et al.; Baculoviruses were engineered to express hemagglutinin (HA) genes of recent avian influenza (AI) isolates of the H5 and H7 subtypes . The proteins were expressed as either intact (H7) or slightly truncated versions (H5) . In both cases purified HA proteins from insect cell cultures retained hemagglutination activity and formed rosettes in solution, indicating proper folding . Although immunogenic in this form, these proteins were more effective when administered subcutaneously in a water-in-oil emulsion . One or two-day-old specific pathogen free (SPF) White Rock chickens, free of maternal AI antibodies, responded with variable serum HI titers, but in some cases the titers were comparable to those achieved using whole virus preparations . Vaccination of three-week-old chickens with 1.0 microg of protein per bird generated a more consistent serum antibody response with an average geometric mean titer (GMT) of 121 (H5) and 293 (H7) at 21 days postvaccination . When challenged with highly pathogenic strains of the corresponding AI subtypes, the vaccinated birds were completely protected against lethal infection and in some cases exhibited reduced or no cloacal shedding at 3 days postinfection . Vaccine protocols employing these recombinant HA proteins will not elicit an immune response against internal AI proteins and thus will not interfere with epidemiological surveys of natural influenza infections in the field. Mol Gen Mikrobiol Virusol, 1999, (2), 22 - 9 {Participation of mobile elements in formation of properties of pathogenic bacteria}; Romanova IuM et al.; Published reports about structural organization of genes coding for pathogenicity factors are reviewed . Many of such genes are often united into "virulence blocks" or "pathogenicity islands" and are surrounded by mobile genetic elements, promoting their transposition between related bacteria genomes and leading to changes in virulence in the course of evolution . Data on the similarity of nucleotide sequences of virulence genes in different bacteria are presented, despite differences in their localization in the relevant genomes . The role of rRNA genes in dissemination of virulence genes among different bacteria during transduction or conjugation is shown. Curr Biol, 1999 Jul 1, 9(13), 703 - 6 A missing metabolic pathway in the cattle tick Boophilus microplus; Braz GR et al.; Heme proteins are involved in a wide variety of biological reactions, including respiration, oxygen transport and oxygen metabolism {1} . The heme prosthetic group is synthesized in almost all living organisms except for a few pathogenic bacteria and trypanosomatids that use blood as food {2} {3} . There is a general belief that all nucleated animal cells synthesize heme {1} {4} . However, blood-feeding arthropods ingest enormous amounts of vertebrate blood in a single meal and the heme pathway has not been studied in these animals . We have examined heme synthesis in two hematophagous arthropods - the blood-sucking bug Rhodnius prolixus and the cattle tick Boophilus microplus . We show that R . prolixus makes heme and has a fully operative heme biosynthetic pathway, while B . microplus does not . To our knowledge, this is the first report of an animal that does not synthesize its own heme and relies solely on the recovery of heme present in the diet . Because of the inability of Boophilus to synthesize heme and its ability to deal efficiently with large amounts of free heme, we propose this organism as a good model for studying heme transport and reutilization in animal cells. J Mol Biol, 1999 Jul 9, 290(2), 459 - 70 3D imaging of the 58 kDa cell binding subunit of the Helicobacter pylori cytotoxin; Reyrat JM et al.; Pathogenic strains of Helicobacter pylori produce a potent exotoxin, VacA, which intoxicates gastric epithelial cells and leads to peptic ulcer . The toxin is released from the bacteria as a high molecular mass homo-oligomer of a 95 kDa polypeptide which undergoes specific proteolytic cleavage to 37 kDa and 58 kDa subunits . We have engineered a strain of H . pylori to delete the gene sequence coding for the 37 kDa subunit . The remaining 58 kDa subunit is expressed efficiently and exported as a soluble dimer that is non-toxic but binds target cells in a manner similar to the holotoxin . A 3D reconstruction of the molecule from electron micrographs of quick-freeze, deep-etched preparations reveals the contribution of each building block to the structure and permits the reconstruction of the oligomeric holotoxin starting from individual subunits . In this model P58 subunits are assembled in a ring structure with P37 subunits laying on the top . The data indicate that the 58 kDa subunit is capable of folding autonomously into a discrete structure recognizable within the holotoxin and containing the cell binding domain . Biochemistry, 1999 Jun 29, 38(26), 8304 - 12 Solution structure of the N-terminal F1 module pair from human fibronectin; Potts JR et al.; Multiple sites within the N-terminal domain (1-5F1) of fibronectin have been implicated previously in fibronectin matrix assembly, heparin binding, and binding to cell surface proteins of pathogenic bacteria . The solution structure of 1F1(2)F1, the N-terminal F1 module pair from human fibronectin, has been determined using NMR spectroscopy . Both modules in the pair conform to the F1 consensus fold . In 4F1(5)F1, the only other F1 module pair structure available, there is a well-defined intermodule interface; in 1F1(2)F1, however, there is no detectable interface between the modules . Comparison of the backbone 15N- inverted question mark1H inverted question mark NOE values for both module pairs confirms that the longer intermodule sequence in 1F1(2)F1 is flexible and that the stabilization of the 4F1 C-D loop observed in 4F1(5)F1, as a result of the intermodule interface, is not observed in 1F1(2)F1. Ital J Gastroenterol Hepatol, 1999 Apr, 31(3), 186 - 91 Food allergy and Helicobacter pylori infection; Figura N et al.; BACKGROUND: Most antigens reach the immune system through mucosae . Gastrointestinal mucosa is a barrier for alimentary antigens . Inflammatory processes, such as Helicobacter pylori-associated gastritis, could alter the integrity of the gastric barrier, increase the mucosal permeability, and enhance crossing of food antigens which may stimulate allergic reactions . PURPOSE: The aim of this study was to establish whether patients with symptomatic food allergy and detectable immunoglobulin E (IgE) to alimentary antigens were infected by Helicobacter pylori more often than controls, and to determine the phenotype of the infecting Helicobacter pylori . PATIENTS AND METHODS: Thirty-eight consecutive patients with symptomatic food allergy and serum IgE to alimentary antigens, and 53 consecutive age-matched controls (subjects without food allergy and detectable levels of IgE anti-alimentary antigens) living in the same area and attending the same institution were investigated serologically to determine the prevalence of Helicobacter pylori infection, and an immune response to CagA, a marker of the most pathogenic strains . IgE to alimentary allergens were measured by a commercial kit . RESULTS: The prevalence of Helicobacter pylori infection in patients with food allergy and controls was similar (42.1% and 47.1%, respectively) . Anti-CagA antibodies in Helicobacter pylori-infected persons were detected in 62.5% of patients with food allergy, and 28.0% of controls (p = 0.030, odds ratio = 4.29, RR = 2.23) . The mean IgE level to the most common alimentary antigens was increased in CagA-positive, with respect to the CagA-negative, patients . CONCLUSIONS: The enhanced mucosal and inflammatory lesions commonly found in individuals infected by CagA-positive Helicobacter pylori strains could increase the epithelial permeability and render non-selective the passage of allergens which, in atopic persons, could directly stimulate an IgE response . Infection by CagA-positive Helicobacter pylori may increase the risk of food allergy. Yale J Biol Med, 1998 Mar-Apr, 71(2), 63 - 73 Structure, function and localization of Helicobacter pylori urease; Dunn BE et al.; Helicobacter pylori is the causative agent of most cases of gastritis . Once acquired, H . pylori establishes chronic persistent infection; it is this long-term infection that, is a subset of patients, leads to gastric or duodenal ulcer, gastric cancer or gastric MALT lymphoma . All fresh isolates of H . pylori express significant urease activity, which is essential to survival and pathogenesis of the bacterium . A significant fraction of urease is associated with the surface of H . pylori both in vivo and in vitro . Surface-associated urease is essential for H . pylori to resist exposure to acid in the presence of urea . The mechanism whereby urease becomes associated with the surface of H . pylori is unique . This process, which we term "altruistic autolysis," involves release of urease (and other cytoplasmic proteins) by genetically programmed autolysis with subsequent adsorption of the released urease onto the surface of neighboring intact bacteria . To our knowledge, this is the first evidence of essential communal behavior in pathogenic bacteria; such behavior is crucial to understanding the pathogenesis of H . pylori. FEBS Lett, 1999 Jun 4, 452(1-2), 16 - 21 Molecular and cellular activities of Helicobacter pylori pathogenic factors; Montecucco C et al.; Stomach infection with pathogenic strains of Helicobacter pylori causes in some patients severe gastroduodenal diseases . These bacteria produce various virulence factors and, here, we review the recent acquisition on the biochemical mode of action of three major factors . We discuss the role of urease both as buffer of the stomach pH and as source of ammonia . The vacuolating toxin alters the endocytic pathway of non-polarized cells, inducing the release of acid hydrolases, the depression of extracellular ligand degradation and of antigen processing and, in the presence of ammonia, swelling of late-prelysosomal compartments . In polarized epithelial monolayers, vacuolating toxin induces an increase of the paracellular permeability, independent of vacuolation . The neutrophil activating protein induces the production of oxygen radicals in human neutrophils and could contribute to the damage of the stomach mucosa . The activities of these factors are discussed in terms of the need of the bacterium of increasing the supply of nutrients from the stomach lumen and from the mucosa. Trop Anim Health Prod, 1999 Apr, 31(2), 75 - 81 Susceptibility of local Nigerian and exotic chickens to infectious bursal disease by contact exposure; Okoye JO et al.; One hundred 6-week-old susceptible cockerels were inoculated with a pathogenic strain of infectious bursal disease virus (IBDV) and kept in the same pen as 100 each of 6-week-old pullets, local chickens and broilers . The cockerels developed depression and diarrhoea on day 3 post inoculation (PI) and most of the pullets and some of the local chickens and broilers showed similar signs on day 4 PI . Loss in weight was severe and similar in the pullets and local chickens, being significantly greater than that in the broilers from days 3-11 PI . The total mortality was 85%, 66.7%, 30% and 20% for the pullets, cockerels, local chickens and broilers, respectively . The lesions were more severe in the pullets and local chickens than in the broilers . IBDV antigen and antibody were detected, respectively, in all the bursal and serum samples from the infected chickens tested . The contact exposure method used in this study simulates better what happens in nature than inoculation with IBDV . The reduced mortality observed among the local chickens, compared with that (61.5%) seen in earlier studies using intraocular inoculation of IBDV, may have been due to behavioural differences that tend to result in their ingesting a relatively low dose of the virus. Rapid Commun Mass Spectrom, 1999, 13(11), 1067 - 71 Fingerprinting of Helicobacter pylori strains by matrix-assisted laser desorption/ionization mass spectrometric analysis; Nilsson CL; Helicobacter pylori is an important human gastrointestinal pathogenic bacterium which is believed to colonize approximately one-half of the world's population . Different strains of H . pylori possess virulence proteins for tissue colonization, host evasion and tissue damage . The bacteria display genomic instabilities that include gene rearrangements and gene exchange . Recently, methods for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) have been established for monitoring biomarkers in bacterial extracts . In order to establish a set of H . pylori specific biomarkers as well as a set of strain-specific biomarkers, we examined lysates and extracts from six different strains of this bacterium . Three different MALDI matrices, alpha-cyano-4-hydroxycinnamic acid, sinapinic acid, and ferulic acid were tested for sensitivity of analysis . Also, the effects of solubilizing analytes with the detergent n-octyl-beta-D-glucopyranoside were explored . It was found that a set of H . pylori specific, and a probable set of strain-specific, biomarkers could be established using MALDI-TOFMS . The use of H . pylori fingerprinting by MALDI may be useful for typing of these bacteria, or for studying genetic drift at the phenotypic level in specific strains. Virology, 1999 Jun 20, 259(1), 166 - 75 Pathogenicity and comparative evolution in vivo of the transitional quasispecies SIVsmmPBj8; Tao B et al.; During 14 months of infection of a pig-tailed macaque, the acutely lethal simian immunodeficiency virus SIVsmmPBj14 (SIV-PBj14) evolved from the minimally pathogenic strain SIVsmm9 . The virus isolated at 8 months (SIV-PBj8) exhibited properties of both SIVsmm9 and SIV-PBj14, indicating that a phenotypic transition occurred between 6 and 10 months . To assess the influence that this new composition of biologic properties might have on pathogenicity, three pig-tailed macaques were inoculated intravenously with SIV-PBj8 . Although no animals developed the severe acute disease syndrome typical of SIV-PBj14, all had high levels of viremia and died of AIDS at 4, 10 . 5, and 32 months . Characterization of the SIV-PBj8-derived quasispecies that evolved in these macaques showed that at 4 days after inoculation, viruses from all three animals exhibited in vitro properties different from those of the inoculum . By 4 months, the initial phenotypic profiles had changed, with the quasispecies in plasma from the animal (J90232) that died at this time most closely resembling SIV-PBj14, not SIV-PBj8 . Phylogenetic trees of the gp41/Nef region of viruses in 4-month plasma from J90232 revealed three distinct populations with high bootstrap values: one group branched with SIVsmm9, one with SIV-PBj14, and one with SIV-PBj8 (ratio of clones, 5:9:5) . Nucleotide sequence analysis suggested that some members of the original SIV-PBj8 quasispecies may have been evolving toward a SIV-PBj14-like genotype at the time macaque J90232 died . The use of SIV-PBj8, which was more pathogenic than SIVsmm9, but less pathogenic than SIV-PBj14, may provide the optimal genetic background on which to identify the minimal, multigenic determinants of the SIV-PBj14 phenotype . The results of our studies on SIV-PBj14 indicate that in some, but not all, cases of primate lentivirus infection more pathogenic variants evolve, selectively proliferate, and more than likely contribute to disease progression . Br J Nurs, 1999 Mar 11-24, 8(5), 313 - 7 Algosteril calcium alginate dressing for moderate/high exudate; Williams C; Algosteril is a new alginate dressing manufactured by Les Laboratoires BROTHIER and distributed by Beiersdorf Medical . It is a natural, pure, non-woven dressing made from calcium alginate fibres . It complements other products in the Beiersdorf wound care family such as Cutinova, Cutifilm and Cutisorb . Algosteril rapidly absorbs and retains wound fluid to form an integral gellified structure, thereby maintaining an ideal moist wound healing environment . It traps and immobilizes pathogenic bacteria in the network of gellified fibres, stimulates macrophage activity and activates platelets, resulting in haemostasis and accelerated wound healing. AIDS Res Hum Retroviruses, 1999 May 20, 15(8), 721 - 9 Sequential analysis of apoptosis induction in peripheral blood mononuclear cells and lymph nodes in the early phase of pathogenic and nonpathogenic SIVmac infection; Iida T et al.; To investigate the role of apoptosis in the early phase of HIV infection, we used macaques infected with simian immunodeficiency virus strain mac (SIVmac) as a primate model and examined sequentially the characteristics of apoptosis of lymphocytes in peripheral blood mononuclear cells (PBMCs) and lymph nodes in the early phase of SIVmac infection . Five macaques infected with a pathogenic strain of SIV, SIVmac239, were analyzed during the first 4 weeks after infection . Peripheral CD4+ and CD8+ cells transiently decreased at 1 week postinfection . The percentage of apoptotic cells in cultured PBMCs increased from about 2 weeks postinfection . The number of apoptotic cells in lymph node sections was higher on days 13 and 28 postinfection than before infection and on day 5 postinfection . Fas antigen expression on peripheral lymphocytes was upregulated from day 8 postinfection . These results indicate that apoptosis is induced about 2 weeks after SIVmac239 infection, following the upregulation of Fas antigen expression on lymphocytes . Since apoptosis was induced about 1 week after the decrease in peripheral CD4+ and CD8+ cell counts, it appears that the apoptosis induction does not play an important role in the transient lymphopenia in the early phase of SIVmac infection . In macaques infected with a nonpathogenic derivative of SIVmac239, SIVmac delta nef, apoptosis of lymphocytes was induced as it was in SIVmac239-infected macaques, but to a lesser degree, suggesting a correlation between the extent of apoptosis induction in lymphocytes in the early phase of SIVmac infection and the pathogenicity of SIVmac. J Gen Intern Med, 1999 Jun, 14(6), 373 - 5 Adhesive tape and intravascular-catheter-associated infections; Redelmeier DA et al.; Adhesive tape is placed in close contact with intravascular catheters for extended periods and could theoretically contribute to local infections . We found that 74% of specimens of tape collected in one hospital were colonized by pathogenic bacteria . However, only 5% of specimens had significant growth from an inner layer obtained by discarding the outside layer from each roll . We suggest that adhesive tape is a potential source of pathogenic bacteria and that discarding the outer layer from a partially used roll might be a simple method for reducing the risk of infection to patients. Infect Immun, 1999 Jun, 67(6), 3066 - 72 Acute clinical disease in cats following infection with a pathogenic strain of Bartonella henselae (LSU16); O'Reilly KL et al.; Bartonella henselae is the causative agent of human cat scratch disease as well as several serious sequelae of infections, including bacillary angiomatosis and bacillary peliosis . Conflicting reports describe the pathogenesis of B . henselae in the cat . In this study, we characterized a strain of B . henselae termed LSU16 . This strain was isolated on rabbit blood agar from a naturally infected 10-month-old female cat during a recurrent episode of bacteremia . The bacterial species was confirmed by PCR-restriction fragment length polymorphism analysis . Nine cats were infected intradermally with 5 x 10(7) CFU of LSU16, and clinical signs, antibody responses, and bacteremia were monitored . All nine cats developed raised, erythematous areas at the site of inoculation within 72 h postinoculation; the swelling peaked at 14 days postinfection and was not palpable by 28 days postinfection . Fever developed in all nine cats between 6 and 16 days postinfection and lasted for 1 to 8 days . Between 6 and 16 days postinfection, all nine cats experienced lethargy which persisted 5 to 18 days . Seven of nine cats were bacteremic by day 7, and all nine cats had become bacteremic by 14 days postinfection . Bacteremia peaked at 14 to 28 days postinfection in all cats . In six of the nine infected cats, bacterial numbers reached nondetectable levels during the 7th week postinfection; however, a single animal maintained bacteremia to 18 weeks postinfection . All nine cats developed strong antibody responses to B . henselae, as determined by Western blot analysis and enzyme-linked immunosorbent assay . Subsequently, three naive cats were injected intradermally with blood from cats infected with LSU16 from a pure culture, and five naive cats were injected with feces from fleas which had been feeding on cats infected with a pure culture of LSU16 . These cats developed signs similar to those described in the previous experiment and were euthanized at 5 weeks postinfection . We conclude that B . henselae LSU16 is a virulent strain of B . henselae in cats and propose that the virulence of B . henselae in cats is strain dependent. Infect Immun, 1999 Jun, 67(6), 2841 - 6 Inhibition of osteoblastic cell differentiation by lipopolysaccharide extract from Porphyromonas gingivalis; Kadono H et al.; Lipopolysaccharide from Porphyromonas gingivalis (P-LPS), an important pathogenic bacterium, is closely associated with inflammatory destruction of periodontal tissues . P-LPS induces the release of cytokines and local factors from inflammatory cells, stimulates osteoclastic-cell differentiation, and causes alveolar bone resorption . However, the effect of P-LPS on osteoblastic-cell differentiation remains unclear . In this study, we investigated the effect of P-LPS extract prepared by the hot-phenol-water method, on the differentiation of primary fetal rat calvaria (RC) cells, which contain a subpopulation of osteoprogenitor cells, into osteoblastic cells . P-LPS extract significantly inhibited bone nodule (BN) formation and the activity of alkaline phosphatase (ALPase), an osteoblastic marker, in a dose-dependent manner (0 to 100 ng of P-LPS extract per ml) . P-LPS extract (100 ng/ml) significantly decreased BN formation to 27% of the control value and inhibited ALPase activity to approximately 60% of the control level on days 10 to 21 but did not affect RC cell proliferation and viability . P-LPS extract time-dependently suppressed the expression of ALPase mRNA, with an inhibitory pattern similar to that of enzyme activity . The expression of mRNAs for osteocalcin and osteopontin, matrix proteins related to bone metabolism, was markedly suppressed by P-LPS extract . Furthermore, P-LPS extract increased the expression of mRNAs for CD14, LPS receptor, and interleukin-1beta in RC cells . These results indicate that P-LPS inhibits osteoblastic-cell differentiation and suggest that LPS-induced bone resorption in periodontal disease may be mediated by effects on osteoblastic as well as osteoclastic cells. APMIS, 1999 May, 107(5), 455 - 73 Infection, inflammation and sleep: more pieces to the puzzle of sudden infant death syndrome (SIDS); Blackwell CC et al.; Risk factors for sudden infant death syndrome (SIDS) parallel those for respiratory tract infections; however, infectious agents suggested to be involved in SIDS do not fulfil Koch's postulates . No single agent has been identified in all cases and there is no suitable animal model for SIDS which could be used to test the candidate organisms . Based on epidemiological and experimental work by our group and others, we suggested some SIDS deaths are due to pathophysiological responses elicited by combinations of microbial products and/or cigarette smoke during a developmental stage when infants' endocrine responses are less able to "damp down" the effects of inflammatory mediators . Here we review evidence from studies on interactions between developmental and environmental risk factors that could affect 1) mucosal colonization of infants by potentially pathogenic bacteria, and 2) induction and control of infants', inflammatory responses to infectious agents . New evidence suggests that there are genetic factors involved in the induction of inflammatory responses to some bacterial antigens implicated in SIDS . Further investigation of the role of infection, exposure to cigarette smoke and inflammation in infants, particularly differences in ethnic groups at increased risk of SIDS, could lead to new insights into the events leading to a fatal outcome and perhaps to new intervention schemes to reduce further the incidence of these deaths. Int Endod J, 1997 Mar, 30(2), 102 - 14 Tissue response to potential root-end filling materials in infected root canals; Chong BS et al.; The tissue responses to two potential root-end filling materials, a light-cured glass ionomer cement (Vitrebond) and a reinforced zinc oxide-eugenol cement (Kalzinol) were compared with that to amalgam . In 27 premolar teeth of beagle dogs (54 roots), a collection of endodontic pathogenic bacteria was first inoculated into the root canals to induce periapical lesions . On each root, an apicectomy was performed and root-end cavities prepared to receive fillings of each material . The teeth and surrounding jaw were removed after 8 weeks (24 roots) and 4 weeks (30 roots); and they were prepared for histological examination . The tissue response to amalgam fillings after 4 and 8 weeks was marked by moderate or severe inflammation on all roots, and extended > 0.5 mm in 10 out of 18 roots . In contrast, after 8 weeks, the majority of roots filled with Kalzinol showed little or moderate inflammation while the tissue response to Vitrebond was the best of the three materials, and was also less extensive . After 4 weeks, the overall best tissue response was with Kalzinol, followed closely by Vitrebond . The differences between materials for both time periods with either none or few inflammatory cells when compared with that with either moderate or severe inflammation were statistically significant (P < 0.01) . Similarly, the differences between materials for both time periods with no inflammation or inflammation extending < 0.2 mm when compared with that with inflammation extending > 0.2 mm (< or = 0.5 mm or > 0.5 mm) were statistically significant (P < 0.01) . Both Vitrebond and Kalzinol have potential as root-end filling materials as the tissue response was considerably more favourable than that to amalgam. Lakartidningen, 1999 Apr 21, 96(16), 1965 - 6 {Fluoroquinolone resistance of human pathogenic bacteria . Resistant E coli now appearing in Sweden}; Osterlund A et al.; Fluoroquinolone-resistance is a growing international problem . Warnings have earlier been issued concerning the risk of resistance development due to excessive fluoroquinolone prescription . The development of resistance among E . coli strains isolated from primary care patients with UTI is now apparent in Sweden . So far the majority of these strains manifest only low-level resistance . However, in view of the risk of high-level resistance developing among these strains further exposed to fluoroquinolones, it is important to think twice before prescribing these drugs. Acta Crystallogr D Biol Crystallogr, 1999 Jun, 55 ( Pt 6), 1198 - 200 Crystallization and preliminary X-ray diffraction analysis of a biologically active fragment of CD55; Lea S et al.; Crystals have been grown of two of the domains of CD55 . This is the first report of crystallization of a short consensus repeat (SCR) domain containing protein . CD55 is a widely expressed polymorphic glycoprotein, which functions as a complement regulator by inhibiting assembly and promoting destruction of C3 and C5 convertases . As a key regulator of complement, CD55 is implicated in the hyperacute rejection of xenografts from pigs into primates . It is also commonly hijacked as a receptor by viruses (e.g . medically important echoviruses and coxsackieviruses) and bacterial pathogens (e.g . certain pathogenic strains of Escherichia coli) . Here, crystallization of a virus-binding fragment expressed in yeast, consisting of two of the four extracellular SCR domains of CD55, is reported . The recombinant domains have been crystallized in 30% polyethylene glycol (PEG), 0.2 M sodium acetate, 0.1 M sodium acetate trihydrate pH 4.6 using the sitting-drop vapour-diffusion method . Two crystal forms are observed (orthorhombic and monoclinic) and a native data set to 1.65 A resolution has been collected from the monoclinic form at the Synchrotron Radiation Source, Daresbury, UK. J Esthet Dent, 1998, 10(5), 265 - 71 Periodontal diseases and dental implants in older adults; Wilson TG Jr et al.; Older adults present special problems for the dentist trying to establish or reestablish esthetics . Periodontal diseases are of concern for this population since tooth loss from these widespread problems increases with age . In general, this loss occurs because of increased exposure time to pathogenic bacteria, not some change inherent in the body brought on by the aging process . The profession has begun to place more emphasis on systemic risk factors and their role in modifying periodontal inflammation . The current thinking is that bacteria are necessary to initiate and sustain periodontal diseases, but the clinical manifestation is dictated to a significant extent by systemic factors . Smoking, diabetes, and being positive for the interleukin-1 genotype predispose the patient to developing more severe disease . For those older adults who lose teeth, dental implants have emerged as reliable replacements, and concerns about placing these devices in patients who have lost teeth as a result of periodontitis appear to be largely unfounded. Front Biosci, 1999 May 01, 4, D433 - 56 Conjugative transfer in the dissemination of beta-lactam and aminoglycoside resistance; Waters VL; The dissemination of antibiotic resistance among pathogenic bacteria can be attributed largely to conjugative DNA transfer . The general category of conjugative transfer includes both bacterial plasmid conjugation and the transfer of nonreplicative conjugative transposons . Prototypes for these two systems are the plasmid RK2 and the conjugative transposon Tn916 . To address the long-term problem of the increasing prevalence and severity of antibiotic resistance, strategies aimed against conjugative transfer are needed, but their development will require a greater understanding of conjugative resistance gene acquisition . Overviews of the two conjugative transfer systems are presented, to summarize and compare current concepts . Observations regarding transfer of conjugative transposons is consistent with the prevailing model for plasmid conjugation, that is, by the transfer of a single-stranded DNA molecule from the donor to the recipient bacterium, and the generation of the single strand by rolling circle DNA replication . The relevance of vegetative plasmid replication and host range to the spread of multiple drug resistance is discussed, and clinical examples of conjugative transfer of multiple antibiotic resistance illustrate the severity of the current situation . Possible directions, traditional and innovative, are offered to address the conjugative transfer problem in drug resistance, and potentially to break the cycle of antibiotic development followed by the bacterial resistance gene acquisition. J Clin Periodontol, 1999 Apr, 26(4), 257 - 60 Tissue necrosis after subgingival irrigation with fluoride solution; Sjostrom S et al.; Irrigation of periodontal pockets with fluoride solution after scaling and root planing is occasionally recommended to inhibit the growth of pathogenic bacteria in the periodontal pocket . At the same time, irrigation enables mechanical removal of loosely adhering plaque and debris . Due to its toxicity, fluoride solution deposited in the periodontium may lead to tissue damage . We report in this paper, a case of extensive periodontal tissue necrosis and permanent loss of alveolar bone after irrigation of periodontal pockets with stannous fluoride solution . The literature on the toxic effects of fluoride on the local tissues is briefly reviewed and arguments for a re-evaluation of the use of stannous fluoride for pocket irrigation are provided. Trends Microbiol, 1999 Mar, 7(3), 111 - 5 Bacterial tellurite resistance; Taylor DE; Tellurium compounds are used in several industrial processes, although they are relatively rare in the environment . Genes associated with tellurite resistance (TeR) are found in many pathogenic bacteria . Tellurite can be detoxified through interactions with cellular thiols, such as glutathione, or a methyltransferase-catalyzed reaction, although neither process appears involved in plasmid-mediated TeR. Virology, 1999 Apr 25, 257(1), 15 - 23 Hyaluronan synthesis in virus PBCV-1-infected chlorella-like green algae; Graves MV et al.; We previously reported that the chlorella virus PBCV-1 genome encodes an authentic, membrane-associated glycosyltransferase, hyaluronan synthase (HAS) . Hyaluronan, a linear polysaccharide chain composed of alternating beta1,4-glucuronic acid and beta1, 3-N-acetylglucosamine groups, is present in vertebrates as well as a few pathogenic bacteria . Studies of infected cells show that the transcription of the PBCV-1 has gene begins within 10 min of virus infection and ends at 60-90 min postinfection . The hyaluronan polysaccharide begins to accumulate as hyaluronan-lyase sensitive, hair-like fibers on the outside of the chlorella cell wall by 15-30 min postinfection; by 240 min postinfection, the infected cells are coated with a dense fibrous network . This hyaluronan slightly reduces attachment of a second chlorella virus to the infected algae . An analysis of 41 additional chlorella viruses indicates that many, but not all, produce hyaluronan during infection . J Periodontal Res, 1999 Feb, 34(2), 70 - 8 In vitro studies of lymphocyte apoptosis induced by the periodontal pathogen Porphyromonas gingivalis; Geatch DR et al.; Apoptosis has a physiological role in lymphocyte development and function serving to remove self-reactive T-cells in the thymus as well as activated peripheral T-cells when they are no longer required in the immune response . Evidence from the study of several pathogenic bacteria indicate that induction of premature cell death by apoptosis may be an important pathogenic mechanism promoting infection, inflammation and concomitant disease . In this paper we demonstrate that cultures of the periodontal pathogen Porphyromonas gingivalis (P . gingivalis) promote lymphocyte apoptosis in peripheral blood mononuclear cells (PBMC) . We have used assays designed to investigate the different molecular and cellular changes associated with apoptosis . Thus flow cytometry revealed that whole cultures of P . gingivalis promoted cell shrinkage in the lymphocyte fraction of PBMC and analysis of hypodiploidy confirmed that the cellular changes were associated with nuclear changes characteristic of apoptosis . We also found that apoptosis was promoted in PBMC exposed to both whole P . gingivalis cultures and culture supernatant but not washed bacterial cells; this indicates that molecule(s) secreted into the medium were responsible for this activity and not a factor intrinsic to the bacterial cell . Furthermore heat treatment has no effect on the ability of P . gingivalis cultures to induce lymphocyte apoptosis . In summary, a soluble heat stable component of the supernatant from P . gingivalis cultures promotes lymphocyte apoptosis . These data establish the principle that bacteria-induced apoptosis may be an important feature of the pathogenesis of periodontal disease. Nat Struct Biol, 1999 Apr, 6(4), 366 - 73 NMR structure of the Tn916 integrase-DNA complex; Wojciak JM et al.; The integrase protein catalyzes the excision and integration of the Tn916 conjugative transposon, a promiscuous genetic element that spreads antibiotic resistance in pathogenic bacteria . The solution structure of the N-terminal domain of the Tn916 integrase protein bound to its DNA-binding site within the transposon arm has been determined . The structure reveals an interesting mode of DNA recognition, in which the face of a three-stranded antiparallel beta-sheet is positioned within the major groove . A comparison to the structure of the homing endonuclease I-Ppol-DNA complex suggests that the three-stranded sheet may represent a new DNA-binding motif whose residue composition and position within the major groove are varied to alter specificity . The structure also provides insights into the mechanism of conjugative transposition . The DNA in the complex is bent approximately 35 degrees and may, together with potential interactions between bound integrase proteins at directly repeated sites, significantly bend the arms of the transposon. J Bacteriol, 1999 Apr, 181(8), 2477 - 84 Isolation of Helicobacter pylori genes that modulate urease activity; McGee DJ et al.; Helicobacter pylori urease, a nickel-requiring metalloenzyme, hydrolyzes urea to NH3 and CO2 . We sought to identify H . pylori genes that modulate urease activity by constructing pHP8080, a plasmid which encodes both H . pylori urease and the NixA nickel transporter . Escherichia coli SE5000 and DH5alpha transformed with pHP8080 resulted in a high-level urease producer and a low-level urease producer, respectively . An H . pylori DNA library was cotransformed into SE5000 (pHP8080) and DH5alpha (pHP8080) and was screened for cotransformants expressing either lowered or heightened urease activity, respectively . Among the clones carrying urease-enhancing factors, 21 of 23 contained hp0548, a gene that potentially encodes a DNA helicase found within the cag pathogenicity island, and hp0511, a gene that potentially encodes a lipoprotein . Each of these genes, when subcloned, conferred a urease-enhancing activity in E . coli (pHP8080) compared with the vector control . Among clones carrying urease-decreasing factors, 11 of 13 clones contained the flbA (also known as flhA) flagellar biosynthesis/regulatory gene (hp1041), an lcrD homolog . The LcrD protein family is involved in type III secretion and flagellar secretion in pathogenic bacteria . Almost no urease activity was detected in E . coli (pHP8080) containing the subcloned flbA gene . Furthermore, there was significantly reduced synthesis of the urease structural subunits in E . coli (pHP8080) containing the flbA gene, as determined by Western blot analysis with UreA and UreB antiserum . Thus, flagellar biosynthesis and urease activity may be linked in H . pylori . These results suggest that H . pylori genes may modulate urease activity. Virology, 1999 Apr 10, 256(2), 340 - 50 The genome nucleotide sequence of a contemporary wild strain of measles virus and its comparison with the classical Edmonston strain genome; Takeda M et al.; The only complete genome nucleotide sequences of measles virus (MeV) reported to date have been for the Edmonston (Ed) strain and derivatives, which were isolated decades ago, passaged extensively under laboratory conditions, and appeared to be nonpathogenic . Partial sequencing of many other strains has identified >/=15 genotypes . Most recent isolates, including those typically pathogenic, belong to genotypes distinct from the Edmonston type . Therefore, the sequence of Ed and related strains may not be representative of those of pathological measles circulating at that or any time in human populations . Taking into account these issues as well as the fact that so many studies have been based upon Ed-related strains, we have sequenced the entire genome of a recently isolated pathogenic strain, 9301B . Between this recent isolate and the classical Ed strain, there were 465 nucleotide differences (2.93%) and 114 amino acid differences (2.19%) . Computation of nonsynonymous and synonymous substitutions in open reading frames as well as direct comparisons of noncoding regions of each gene and extracistronic regulatory regions clearly revealed the regions where changes have been permissible and nonpermissible . Notably, considerable nonsynonymous substitutions appeared to be permissible for the P frame to maintain a high degree of sequence conservation for the overlapping C frame . However, the cause and the effect were largely unclear for any substitution, indicating that there is a considerable gap between the two strains that cannot be filled . The sequence reported here would be useful as a reference of contemporary wild-type MeV . J Eur Acad Dermatol Venereol, 1999 Jan, 12(1), 25 - 9 Altered sperm function or sperm antibodies are not associated with chlamydial antibodies in infertile men with leucocytospermia; Habermann B et al.; OBJECTIVE: Leucocytospermia, defined as a concentration of more than 10(6) leucocytes/ml of seminal fluid in patients without clinical symptoms due to an adnexitis, is seen in about 10% of patients in an infertility department . Infection with Chlamydia trachomatis is possibly relevant as other pathogenic bacteria were not cultured from the semen in significant numbers . SETTING: University Clinic, Department of Andrology . PATIENTS: Two hundred and seven patients attending the department for male infertility investigation . METHODS: Analysis on each semen sample included determination of leucocyte count and the MAR test for the detection of sperm antibodies . Chlamydial antibodies in semen were determined using an on-slide enzyme immunoassay . RESULTS: No differences between leucocyte counts in patients with and without chlamydial antibodies were detected . In addition, no differences in the sperm parameters or results of MAR-tests in these two groups was seen . There were no correlations between the leucocyte count and sperm parameters, including the MAR-test results . CONCLUSIONS: We conclude that antibodies to chlamydiae in semen are not associated with leucocytospermia . Leucocytospermia per se does not appear to be significant for the sperm functions and immune responses to sperm. J Appl Biomater, 1992 Summer, 3(2), 99 - 115 Polypropylene IUCD retrieval fibers: surface morphology, material properties, microbial attachment, and migration; Coughlin RW et al.; Highly drawn and oriented polypropylene fibers used for the retrieval thread of the Cu-7 intrauterine contraceptive device (IUCD) are compared as to surface morphology and crystallinity with polypropylene fibers prepared under different conditions . A series of experiments also demonstrates the colonization of the surface of polyolefin fibers by pathogenic bacteria that are often found in the human vagina . Moreover, it is demonstrated that the retrieval threads appear to encourage pathogenic bacteria to migrate across the surface of agar . The results also indicate that control of drawing and annealing can avoid the surface fibrillation and tendency to fail by separation into a bundle of multifilaments that are observed with the IUCD retrieval threads. J Immunol, 1999 Mar 15, 162(6), 3519 - 26 Modulation of endocytosis in nuclear factor IL-6(-/-) macrophages is responsible for a high susceptibility to intracellular bacterial infection; Pizarro-Cerda J et al.; Activated macrophages kill bacteria, a function known to depend on the expression of NF-IL-6 . Here, it is demonstrated that the attenuated Brucella abortus vaccine strain 19 replicates much better in NF-IL-6-/- than in NF-IL-6(+/+) and NF-IL-6(+/+)-activated murine macrophages and at levels comparable to those observed in normal macrophages infected with the pathogenic strain 2308 . The role of NF-IL-6 in the inhibition of intracellular bacterial replication is related to its control of endocytosis and membrane fusion between endosomes and Brucella-containing phagosomes . Addition of the granulocyte-CSF (G-CSF), whose induction is impaired in NF-IL-6(-/-) macrophages, restores both endocytosis and the morphology of endosomes, together with bactericidal activity . Regulation of membrane traffic in endocytosis by G-CSF whose expression is controlled by NF-IL-6 may explain how a host cell can control intracellular bacterial replication. Lab Anim Sci, 1999 Feb, 49(1), 35 - 41 Lymphoid organ alterations enhanced by sub-lethal doses of coronaviruses in experimentally induced Trypanosoma cruzi infection in mice; Verinaud L et al.; The effect of sub-lethal doses of coronaviruses on the course of disease in CBA mice experimentally infected with a mildly pathogenic strain of Trypanosoma cruzi was investigated . Mice were inoculated with either T . cruzi, 0.1 median lethal dose (LD50) of coronavirus (mouse hepatitis virus {MHV-3} or virus X), or both pathogens . Levels of parasitemia, mortality, and the extent of pathologic alterations in lymphoid organs were determined . Mice inoculated with T . cruzi had mild alterations in their lymphoid organs and survived infection . In contrast, mice inoculated with both pathogens died, and had significantly higher levels of parasitemia and profound alterations in lymphoid organs . These results indicate that the pathologic profile of T . cruzi infection can be profoundly altered by subclinical infection with coronaviruses. Curr Opin Plant Biol, 1998 Aug, 1(4), 329 - 35 Determinants of pathogenicity and avirulence in plant pathogenic bacteria; Collmer A; Many plant pathogenic bacteria possess a conserved protein secretion system that is thought to transfer Avr (avirulence) proteins, with potential activities in both parasitism and defense elicitation, into plant cells . avr genes may be acquired horizontally by these bacteria, and avr gene compositions are highly variable . In the past year, heterologous expression experiments have revealed that the products of avr genes can be interchanged among different genera of bacteria with retention of secretion, pathogenicity, and avirulence activities, suggesting mechanisms for rapid coevolution of these parasites with changing plant hosts. Curr Opin Microbiol, 1998 Feb, 1(1), 17 - 26 In vivo and ex vivo regulation of bacterial virulence gene expression; Cotter PA et al.; Bacteria are remarkably adaptable organisms that are able to survive and multiply in diverse and sometimes hostile environments . Adaptability is determined by the complement of genetic information available to an organism and by the mechanisms that control gene expression . In general, gene products conferring a growth or survival advantage in a particular situation are expressed, while unnecessary or deleterious functions are not . Expression of virulence gene products that allow pathogenic bacteria to multiply on and within host cells and tissues are no exception to this rule . Being of little or no use to the bacterium except during specific stages of the infectious cycle, these accessory factors are nearly always subject to tight and coordinate regulation . As a result of recent advances, we are beginning to appreciate the complexities of the interactions between bacteria and their hosts . The ability to probe virulence gene regulation in vivo has broadened our perspectives on pathogenesis. Indian J Gastroenterol, 1999 Jan-Mar, 18(1), 18 - 21 Isoenzyme and molecular characterization of Entamoeba histolytica and Entamoeba dispar isolates from symptomatic and asymptomatic subjects; Sinha P et al.; AIM: To correlate the clinical features of amebic infections with the characteristics of Entamoeba culture isolates of stools . METHODS: Isolates from seven irritable bowel syndrome (IBS) patients, four asymptomatic cyst passers (ACP) and five patients with invasive amebic disease were subjected to hexokinase polyacrylamide electrophoresis (HK-PAGE) and their DNA subjected to restriction fragment (RF) analysis of amplified polymerase chain reaction (PCR) products . These findings were correlated with anti-amebic serology . Two axenic pathogenic strains (HM1:IMSS, NIH:200) and one xenic nonpathogenic strain (SAW1734) were used as standards . RESULTS: All isolates from IBS patients as well as ACP had slow-moving (nonpathogenic) band pattern, whereas those from patients with invasive disease had fast-moving (pathogenic) band pattern on HK-PAGE . Serological data using EIA and RF patterns of PCR-amplified genome corroborated these results . CONCLUSIONS: Our results support the view that there are two species of Entamoeba infecting humans--E . histolytica(pathogenic) and E . dispar (nonpathogenic), and HK-PAGE of culture isolates can differentiate between them. Proc Natl Acad Sci U S A, 1999 Mar 2, 96(5), 2001 - 6 The vacuolating toxin from Helicobacter pylori forms hexameric pores in lipid bilayers at low pH; Czajkowsky DM et al.; Pathogenic strains of Helicobacter pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes . The molecular mechanisms by which VacA causes this vacuolation remain largely unknown . At neutral pH, VacA is predominantly a water-soluble dodecamer formed by two apposing hexamers . In this report, we show by using atomic force microscopy that below pH approximately 5, VacA associates with anionic lipid bilayers to form hexameric membrane-associated complexes . We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into membrane-spanning hexamers . The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation . In addition, electrophysiological measurements indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar lipid bilayers . This low pH-triggered pore formation is likely a critical step in VacA activity. Biochim Biophys Acta, 1999 Feb 16, 1444(2), 263 - 8 Kinetoplast DNA minicircles of Leishmania donovani express a protein product; Singh N et al.; We describe an unprecedented finding of an open reading frame present in the variable region in one of the minicircle sequence classes of a human pathogenic strain of Leishmania donovani (MHOM/IN/90/RMRI 68) which is transcribed and translated . The encoded protein showed homologies to known transport proteins. Prev Vet Med, 1999 Jan 1, 38(1),