The importance of the Rcs phosphorelay in the survival and pathogenesis of the enteropathogenic yersiniae.

The human-pathogenic yersiniae represent an ideal species group to study the evolution of highly virulent bacteria, with Yersinia pestis having emerged from the enteropathogen Y. pseudotuberculosis an estimated 20 000 years ago. Sequence data reveal that the Y. pestis genome is in the early stages of decay and contains hundreds of non-functioning pseudogenes, some of which may be important in the enteric lifestyle of Y. pseudotuberculosis. Bioinformatic analysis of pseudogenes from seven Y. pestis genome sequences identified rcsD as a gene disrupted early in the evolution of this organism. This phosphotransfer protein is part the of the Rcs phosphorelay, a two-component system present in the Enterobacteriaceae which has been shown to regulate the expression of capsular polysaccharide and other virulence determinants in several species including Escherichia coli and Salmonella. Using microarray analysis, we determined that the Y. pseudotuberculosis Rcs phosphorelay regulates the expression of 136 coding sequences, of which 60 % are predicted to affect the cell envelope. Several putative virulence determinants were identified as being regulated by this phosphorelay, along with proteins involved in biofilm formation, motility, mammalian cell adhesion and stress survival. Phenotypic assays on defined mutants confirmed a role for the phosphorelay in these processes in both Y. pseudotuberculosis and Y. enterocolitica

MARCADORES DE PATOGENICIDADE EM Yersinia enterocolitica O: 3 ISOLADAS DE SUÍNOS DO RIO DE JANEIRO Genetic markers of pathogenicity in Yersinia enterocolitica O: 3 isolated from healthy pigs from Rio de Janeiro

Foi realizada a caracterização genotípica e fenotípica de fatores de patogenicidade em 16 amostras de Yersinia enterocolitica O:3 isoladas de suínos sadios do Rio de Janeiro. Foi observado que apenas 6 cepas possuíam o plasmídio de virulência, pYV (+ 70 kb) e apresentavam dependência ao cálcio no meio MOX a 37C. Um plasmídio críptico de cerca de 8,6 kb foi encontrado em uma cepa. Doze cepas revelaram sensibilidade à pesticina enquanto que apenas três se revelaram capazes de hidrolisar a esculina. Através de PCR com "primers" específicos, foi constatada a presença dos genes ail em 14 cepas, irp2, em 1 cepa e a ausência de psaA em todas as cepas analisadas. Quanto aos quimioterápicos, a quase totalidade das cepas mostrou-se ao mesmo tempo resistente à ampicilina e carbenicilina e sensível ao sulfazotrin e à cefoxitina. As respostas foram variadas frente ao cloranfenicol, tetraciclina, kanamicina, gentamicina e ácido nalidíxo.<br>Sixteen Yersinia enterocolitica serotype O:3 strains, isolated from pigs from Rio de Janeiro, have been analyzed for genetic and phenotypic markers of pathogenicity. It was observed that only 6 strains harbored the pYV (+70 kb) plasmid and one strain harbored a small cryptic plasmid of about 8.6 kb. Accordingly only strains harboring pYV were calcium dependent in the MOX medium at 370C. Twelve strains showed pesticin sensitivity and the esculin reaction was negative in 13 strains. PCR analysis of pathogenicity genes using specific primers showed the presence of the ail gene in 14 strains, the irp2 gene in one and the psaA in none. Most of the strains were resistant to ampicillin and carbenicillin, although they were susceptible to sulfazotrin and cefoxitin. For chloramphenicol, tetracycline, kanamycin, gentamicin and nalidixic acid the results varied among the strains