Factors and markers of virulence in Escherichia coli from human septicemia

One hundred Escherichia coli isolates from human septicemia were characterized with respect to O serogroups 1, 2, 4, 6, 7, 8, 15, 18, 75 and 78, alpha-hemolysin, carboxylesterase B typing, cytotoxic necrotizing factor, F165 and CS31A fimbrial antigens, aerobactin production, colicins, and antibiotic sensitivity. A factorial analysis of correspondence and chi 2 tests indicated that most of E. coli isolates belonging to the studied O serogroups were positive for the virulence factors or markers alpha-haemolysin, carboxylesterase B2 type, cytotoxic necrotizing factor, F165 fimbrial antigen and were antibiotic-sensitive (Group I). These characteristics differentiated them from E. coli isolates from other O serogroups which were generally antibiotic resistant and negative for the cited virulence factors and markers (Group II). Aerobactin and colicin production did not differentiate the two E. coli groups. E. coli O serogroups 4 and 6 were highly represented in group I and were responsible for most of the differences between the two groups.