Molecular evidence of clonal Vibrio parahaemolyticus pandemic strains.

The upsurge in worldwide incidence of Vibrio parahaemolyticus infection in the last 5 years has been attributed to the recent appearance of three serotypes with pandemic potential: O3:K6, O4:K68, and O1:K untypeable (KUT). Thirty-five strains of these serotypes, isolated from different countries over 4 years, were characterized by ribotyping and pulsed-field gel electrophoresis to determine their origin. The ribotypes of the strains of these serotypes were indistinguishable, except for a Japanese tdh- negative O3:K6 strain and a U.S. clinical O3:K6 isolate, which had slightly different profiles. The migration patterns of the NotI-digest of the total DNA of the strains were similar, and only slight variations were observed between the serotypes. By contrast, the O3:K6 and O1:KUT strains isolated before 1995 and strains of other serotypes had markedly different profiles. The O4:K68 and O1:KUT strains most likely originated from the pandemic O3:K6 clone

Isolation and molecular characterization of vancomycin-resistant Enterococcus faecium in Malaysia

Nineteen strains of vancomycin-resistant Enterococcus faecium isolated from 10 of 75 (13·3%) tenderloin beef samples were examined for resistance to selected antibiotics, presence of plasmids, and genetic diversity by random amplification of polymorphic DNA analysis. All strains showed multiple resistant to the antibiotics tested. Multiple antibiotic indexing of the vancomycin-resistant E. faecium strains showed that all (100%) originated from high risk contamination environments where antibiotics were often used. Plasmids ranging in size from 1·5 to 36 megadalton were detected in 15 of 19 (79%) strains. Thus, three plasmid profiles and eight antibiotypes were observed among the E. faecium strains. A high degree of polymorphism was obtained by combining the results of the two primers used; with the 19 E. faecium strains being differentiated into 19 RAPD-types. These preliminary results suggest that RAPD-PCR has application for epidemiologic studies and that resistance patterns and plasmid profiling could be used as an adjunct to RAPD for the typing of E. faecium in the study area

Comparative genomic analysis of Vibrio parahaemolyticus: serotype conversion and virulence

<p>Abstract</p> <p>Background</p> <p><it>Vibrio parahaemolyticus </it>is a common cause of foodborne disease. Beginning in 1996, a more virulent strain having serotype O3:K6 caused major outbreaks in India and other parts of the world, resulting in the emergence of a pandemic. Other serovariants of this strain emerged during its dissemination and together with the original O3:K6 were termed strains of the pandemic clone. Two genomes, one of this virulent strain and one pre-pandemic strain have been sequenced. We sequenced four additional genomes of <it>V. parahaemolyticus </it>in this study that were isolated from different geographical regions and time points. Comparative genomic analyses of six strains of <it>V. parahaemolyticus </it>isolated from Asia and Peru were performed in order to advance knowledge concerning the evolution of <it>V. parahaemolyticus</it>; specifically, the genetic changes contributing to serotype conversion and virulence. Two pre-pandemic strains and three pandemic strains, isolated from different geographical regions, were serotype O3:K6 and either toxin profiles (<it>tdh+</it>, <it>trh</it>-) or (<it>tdh-</it>, <it>trh</it>+). The sixth pandemic strain sequenced in this study was serotype O4:K68.</p> <p>Results</p> <p>Genomic analyses revealed that the <it>trh</it>+ and <it>tdh</it>+ strains had different types of pathogenicity islands and mobile elements as well as major structural differences between the <it>tdh </it>pathogenicity islands of the pre-pandemic and pandemic strains. In addition, the results of single nucleotide polymorphism (SNP) analysis showed that 94% of the SNPs between O3:K6 and O4:K68 pandemic isolates were within a 141 kb region surrounding the O- and K-antigen-encoding gene clusters. The "core" genes of <it>V. parahaemolyticus </it>were also compared to those of <it>V. cholerae </it>and <it>V. vulnificus</it>, in order to delineate differences between these three pathogenic species. Approximately one-half (49-59%) of each species' core genes were conserved in all three species, and 14-24% of the core genes were species-specific and in different functional categories.</p> <p>Conclusions</p> <p>Our data support the idea that the pandemic strains are closely related and that recent South American outbreaks of foodborne disease caused by <it>V. parahaemolyticus </it>are closely linked to outbreaks in India. Serotype conversion from O3:K6 to O4:K68 was likely due to a recombination event involving a region much larger than the O-antigen- and K-antigen-encoding gene clusters. Major differences between pathogenicity islands and mobile elements are also likely driving the evolution of <it>V. parahaemolyticus</it>. In addition, our analyses categorized genes that may be useful in differentiating pathogenic Vibrios at the species level.</p

A multi-scale analysis of bull sperm methylome revealed both species peculiarities and conserved tissue-specific

peer-reviewedBackground: Spermatozoa have a remarkable epigenome in line with their degree of specialization, their unique nature and different requirements for successful fertilization. Accordingly, perturbations in the establishment of DNA methylation patterns during male germ cell differentiation have been associated with infertility in several species.Background: Spermatozoa have a remarkable epigenResults: The quantification of DNA methylation at CCGG sites using luminometric methylation assay (LUMA) highlighted the undermethylation of bull sperm compared to the sperm of rams, stallions, mice, goats and men. Total blood cells displayed a similarly high level of methylation in bulls and rams, suggesting that undermethylation of the bovine genome was specific to sperm. Annotation of CCGG sites in different species revealed no striking bias in the distribution of genome features targeted by LUMA that could explain undermethylation of bull sperm. To map DNA methylation at a genome-wide scale, bull sperm was compared with bovine liver, fibroblasts and monocytes using reduced representation bisulfite sequencing (RRBS) and immunoprecipitation of methylated DNA followed by microarray hybridization (MeDIP-chip). These two methods exhibited differences in terms of genome coverage, and consistently, two independent sets of sequences differentially methylated in sperm and somatic cells were identified for RRBS and MeDIP-chip. Remarkably, in the two sets most of the differentially methylated sequences were hypomethylated in sperm. In agreement with previous studies in other species, the sequences that were specifically hypomethylated in bull sperm targeted processes relevant to the germline differentiation program (piRNA metabolism, meiosis, spermatogenesis) and sperm functions (cell adhesion, fertilization), as well as satellites and rDNA repeats. Conclusions: These results highlight the undermethylation of bull spermatozoa when compared with both bovine somatic cells and the sperm of other mammals, and raise questions regarding the dynamics of DNA methylation in bovine male germline. Whether sperm undermethylation has potential interactions with structural variation in the cattle genome may deserve further attention. While bull semen is widely used in artificial insemination, the literature describing DNA methylation in bull spermatozoa is still scarce. The purpose of this study was therefore to characterize the bull sperm methylome relative to both bovine somatic cells and the sperm of other mammals through a multiscale analysis

Bile Acid-Induced Virulence Gene Expression of Vibrio parahaemolyticus Reveals a Novel Therapeutic Potential for Bile Acid Sequestrants

Vibrio parahaemolyticus, a bacterial pathogen, causes human gastroenteritis. A type III secretion system (T3SS2) encoded in pathogenicity island (Vp-PAI) is the main contributor to enterotoxicity and expression of Vp-PAI encoded genes is regulated by two transcriptional regulators, VtrA and VtrB. However, a host-derived inducer for the Vp-PAI genes has not been identified. Here, we demonstrate that bile induces production of T3SS2-related proteins under osmotic conditions equivalent to those in the intestinal lumen. We also show that bile induces vtrA-mediated vtrB transcription. Transcriptome analysis of bile-responsive genes revealed that bile strongly induces expression of Vp-PAI genes in a vtrA-dependent manner. The inducing activity of bile was diminished by treatment with bile acid sequestrant cholestyramine. Finally, we demonstrate an in vivo protective effect of cholestyramine on enterotoxicity and show that similar protection is observed in infection with a different type of V. parahaemolyticus or with non-O1/non-O139 V. cholerae strains of vibrios carrying the same kind of T3SS. In summary, these results provide an insight into how bacteria, through the ingenious action of Vp-PAI genes, can take advantage of an otherwise hostile host environment. The results also reveal a new therapeutic potential for widely used bile acid sequestrants in enteric bacterial infections

The molecular basis of the organization of repetitive DNA-containing constitutive heterochromatin in mammals

International audienc

Isolation and molecular characterization of vancomycinresistant Enterococcus faecium in Malaysia

Nineteen strains of vancomycin-resistant Enterococcus faecium isolated from 10 of 75 (13·3%) tenderloin beef samples were examined for resistance to selected antibiotics, presence of plasmids, and genetic diversity by random amplification of polymorphic DNA analysis. All strains showed multiple resistant to the antibiotics tested. Multiple antibiotic indexing of the vancomycin-resistant E. faecium strains showed that all (100%) originated from high risk contamination environments where antibiotics were often used. Plasmids ranging in size from 1·5 to 36 megadalton were detected in 15 of 19 (79%) strains. Thus, three plasmid profiles and eight antibiotypes were observed among the E. faecium strains. A high degree of polymorphism was obtained by combining the results of the two primers used; with the 19 E. faecium strains being differentiated into 19 RAPD-types. These preliminary results suggest that RAPD-PCR has application for epidemiologic studies and that resistance patterns and plasmid profiling could be used as an adjunct to RAPD for the typing of E. faecium in the study area