Occurrence and characteristics of cytotoxic necrotizing factors, cytolethal distending toxins and other virulence factors in Escherichia coli from human blood and faecal samples

Escherichia coli isolates from human blood (n=266) and faecal (n=237) samples were examined for cytotoxic necrotizing factors 1 and 2 (CNF 1 and 2). cytolethal distending toxin (CDT), and putative Virulence factors that have been associated with disease conditions in humans and animals. PCR showed that the chromosomally encoded, Rho-activating, CNF1 (68/544, 12 center dot 5 %) was more common than the transmissible plasmid-borne CNF2 (3/544, 0 center dot 6%). The relative risk of having either CNF or CDT toxin genes in blood compared to faecal isolates was 3 center dot 88 (95 % CI 2 center dot 36-6 center dot 38). This was highly significant (P<0 center dot 0001) and demonstrates the importance of these factors in bloodstream infections. Fifty-one of 65 (78 %) E. coli bearing CNF1 and 11 of 21 (52%) of E. coli bearing CDT also carried the pyelonephritis-associated pilus gene, papG. The S fimbrial adhesin gene, sfa, was found in 57 blood (21%) and eight faecal samples (3 %). The F 17 fimbrial adhesin gene and afimbrial adhesin gene afa did not occur frequently. Haemolysin (h/y) was found in all of the isolates tested. Further studies must be designed to identify the clinical significance of these genes and their role in pathogenesis.