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EVALUATION OF VIRULENCE MARKERS EXPRESSION IN Bacieroides fragilis

Ferreira, R.*^l, Alexandre, M.C.F.¹, Antunes, E. N. F.¹, Pinhão, A.T.², Moraes, S. R.¹, Domingues, R.M.C.P.¹, and Ferreira, M.C.S.¹ Instituto de Microbiologia - UFRI - Rio de Janeiro, RJ, Brasil ¹ FIOCRUZ - Rio de Janeiro, RJ, Brasil ²

Bacteroides fragilis strains, isolated from different sources (intestinal and extra-intestinal infections, normal flora and environment), were evaluated about the in vitro properties related to interaction between cells. Through assays of agglutination of human erythrocytes, autoagglutination and adherence to human colon carcinoma cells (HT29), different adhesion molecules were detected. The non correlation between properties in the studied strains suggests that independent molecules are involved. Treatments with trypsin, heat and EDTA were capable to inhibit those properties, suggesting a proteic nature for those molecules. The absence of a relation whith the origin of the strains did not allow us to propose the association of any of these activities as virulence markers for the species. As we evaluated the fragilysin expression, a protease associated with damage to intestinal cells and bacterial translocation, we could verify that only those strains originated from diarrhoea were able to express that protease in assays facing HT29 cells, which was confirmed by specific PCR primers for the bft gene. The fragilysin action as enterotoxin was confirmed through the rabbit intestinal ligated loop assay. The association of this property only to strains of intestinal infection origin seems to suggest it as an marker of B. fragilis enterovirulence.

Grants: CNPq, CEPG, FUJB, PRONEX and FINEB-BID