Thirty-seven strains of isolated from bacteraemia and 40 faecal strains isolated from healthy individuals were O serogrouped and investigated for the production of colicins, haemolysin (Hly), cytotoxic necrotising factor (CNF), lethal activity for mice, the expression of P fimbriae, mannose-resistant (MRHA) and mannose-sensitive (MSHA) haemagglutination, and relative cell surface hydrophobicity. Virulence factors significantly associated with bacteraemic strains were: serogroups O2, O4, O6, O7, O8 and O75 (54% 10%, p≪0.001), production of Hly (32% 8%, p≪0.02) and CNF (38% 10%, p≪0.01), expression of P fimbriae (27% 5%, p≪0.02), MRHA types III, IVa and IVb (51% 8%, p≪0.001), and possession of a moderate cell surface hydrophobic charge (35% 13%, p≪0.05). Virulence factors were strongly associated with strains expressing defined MRHA types. Thus, all strains belonging to MRHA types III and IVa were toxigenic, whereas only 11% of strains belonging to MRHA types IVb, V or VI were toxigenic (p≪0.001). Virulence factors were concentrated in strains belonging to O serogroups usually found in that cause extra-intestinal infections, especially in strains of O4 and O6 groups. The most interesting result of this study was that all 12 P-fimbriate strains expressed the MRHA type IVa and 11 of them synthesised CNF.


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