Clonal relationships among Escherichia coli serogroup O78 isolates from human and animal infections.

We investigated the clonal relationships among 63 Escherichia coli strains of antigen serogroup O78 isolated from infections in humans, cattle, sheep, pigs, and chickens. Both septicemic and enterotoxigenic isolates were included in the study. A main group of 55 E. coli strains consisting of 52 septicemic isolates and 3 human enterotoxigenic E. coli isolates were clustered in related clones. The remaining eight strains, four human and four animal isolates, were clonally heterogeneous. The main group of 55 clonally related strains included isolates from human and animal infections. This result indicates that animals are a possible source of serogroup O78 septicemic E. coli infections in humans.