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Binding of SycH Chaperone to YscM1 and YscM2 Activates Effector yop Expression in Yersinia enterocolitica. Eric D. Cambronne, 2004.Yersinia enterocolitica transports YscM1 and YscM2 via the type III pathway, a mechanism that is required for the establishment of bacterial infections . Prior to host cell contact, YscM1 and YscM2 exert posttranscriptional regulation to inhibit expression of effector yop genes, which encode virulence factors that travel the type III pathway into the cytoplasm of macrophages . Relief from repression has been predicted to occur via the type III secretion of YscM1 and YscM2 into the extracellular medium, resulting in the depletion of regulatory molecules from the bacterial cytoplasm . Using digitonin fractionation and fluorescence microscopy of FlAsH-labeled polypeptides in Yersinia-infected cells, we have localized YscM1 and YscM2 within the host cell cytoplasm . Type III injection of YscM1 and YscM2 required the SycH chaperone . Expression of C-terminal fusions of YscM1 and YscM2 to the neomycin phosphotransferase reporter revealed sequences required for regulatory activity and for secretion in the absence of SycH . Coexpression of SycH and glutathione S-transferase (GST)-YscM1 or GST-YscM2, hybrid GST variants that cannot be transported by the type III apparatus, also relieved repression of Yop synthesis . GST-SycH bound to YscM1 and YscM2 and activated effector yop expression without initiation of the bound regulatory molecules into the type III pathway . Further, regulation of yop expression by YscM1, YscM2, and SycH is shown to act independently of factors that regulate secretion, and gel filtration chromotography revealed populations of YscM1 and YscM2 that are not bound to SycH under conditions where Yop synthesis is repressed . Taken together, these results suggest that YscM1- and YscM2-mediated repression may be relieved through binding to the cytoplasmic chaperone SycH prior to their type III injection into host cells . Antibiotic Susceptibility in Relation to Penicillin-Binding Protein Genes and Serotype Distribution of Streptococcus pneumoniae Strains Responsible for Meningitis in Japan, 1999 to 2002. Kimiko Ubukata, 2004.The antibiotic susceptibilities, genotypes of penicillin (PEN)-binding protein genes (pbp), and serotype distributions of Streptococcus pneumoniae isolates from meningitis patients were investigated by a nationwide surveillance group in Japan between 1999 and 2002 . We analyzed 146 isolates from children (  17 years old) and 73 from adults ( 18 years old) . Isolates with or without abnormal pbp1a, pbp2x, or pbp2b genes identified by PCR were classified into six genotype patterns and 90% MIC (MIC90) values for PEN: (i) strains with three normal genes (17.2% of isolates; MIC90, 0.031 µg/ml); (ii) strains with abnormal pbp2x (22.1%, 0.063 µg/ml); (iii) strains with abnormal pbp2b (1.0%, 0.125 µg/ml); (iv) strains with abnormal pbp2x and pbp2b (7.4%, 0.25 µg/ml); (v) strains with abnormal pbp1a and pbp2x (12.7%, 0.25 µg/ml); and (vi) strains with three abnormal PBP genes (39.7%, 4 µg/ml), which are termed genotypic PEN-resistant S . pneumoniae (gPRSP) . Panipenem, a carbapenem, showed an excellent MIC90 (0.125 µg/ml) against gPRSP, followed by meropenem and vancomycin (0.5 µg/ml), cefotaxime and ceftriaxone (1 µg/ml), and ampicillin (4 µg/ml) . Strains of gPRSP were significantly more prevalent in children (45.2%) than in adults (27.4%) . The most frequent serotypes were 6B, 19F, 23F, 6A, and 14 in children and 23F, 22, 3, 10, 6B, and 19F in adults . Serotypes 6B, 6A, 19F, 23F, and 14 predominated among gPRSP . In children, 7- and 11-valent pneumococcal conjugate vaccines would cover 76.2 and 81.3% of isolates, respectively, although coverage would be lower in adults (43.9 and 56.0%, respectively) . These findings suggest the need for early introduction of pneumococcal conjugate vaccines and continuous bacteriological surveillance for meningitis .
Reduction of Escherichia coli O157:H7 Populations in Cattle by Addition of Colicin E7-Producing E . coli to Feed. Gerry P. Schamberger, 2004.A cattle trial using artificially inoculated calves was conducted to determine the effect of the addition of colicinogenic Escherichia coli strains capable of producing colicin E7 (a 61-kDa DNase) to feed on the fecal shedding of serotype O157:H7 . The experiment was divided into three periods . In period 1, which lasted 24 days, six calves were used as controls, and eight calves received 107 CFU of E . coli (a mixture of eight colicinogenic E . coli strains) per g of feed . Both groups were orally inoculated with nalidixic acid-resistant E . coli O157:H7 strains 7 days after the treatment started . In periods 2 and 3, the treatment and control groups were switched, and the colicinogenic E . coli dose was increased 10-fold . During period 3, which lasted as long as period 1, both groups were reinoculated with E . coli O157:H7 . The numbers of E . coli O157:H7 were consistently greater in the control groups during the three periods, but comparisons within each time period determined a statistically significant (P < 0.05) difference only at day 21 of period 1 . However, when the daily average counts were compared between the period 1 control group and the period 3 treatment group that included the same six animals, an overall reduction of 1.1 log10 CFU/g was observed, with a maximum decrease of 1.8 log10 CFU/g at day 21 (overall statistical significance, P = 0.001) . Serotype O157:H7 was detected in 44% of the treatment group's intestinal tissue samples and in 64% of those from the control group (P < 0.04) . These results indicated that the daily addition of 108 CFU of colicin E7-producing E . coli per gram of feed could reduce the fecal shedding of serotype O157:H7 . Pyoverdine-Mediated Regulation of FpvA Synthesis in Pseudomonas aeruginosa: Involvement of a Probable Extracytoplasmic-Function Sigma Factor, FpvI. Gyula Alan Rédly, 2003.A search of the pvd pyoverdine biosynthesis locus of Pseudomonas aeruginosa identified an open reading frame, PA2387, whose product exhibited a sequence similar to those of a number of so-called extracytoplasmic- function sigma factors responsible for siderophore-dependent expression of iron-siderophore receptors in Escherichia coli and Pseudomonas putida . Deletion of this gene, dubbed fpvI, compromised pyoverdine-dependent FpvA ferric pyoverdine receptor production and fpvA gene expression, while the cloned gene stimulated fpvA expression . A Fur-binding site was identified immediately upstream of fpvI, consistent with the observed iron-regulated expression of fpvI and fpvA .
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