Characterization of hemolytic strains of Escherichia coli belonging to classical enteropathogenic O-serogroups.

147 isolates of enteropathogenic E. coli (EPEC) belonging to eleven different O-serogroups were examined for hemolysin-synthesis. Hemolysin-producing (Hly+) strains were found at high frequency in O-serogroups 26 and 114 and at low frequency in O-serogroup 126. The hemolytic activities of EPEC strains of different serogroups were found to be low when compared to Hly+ non-EPEC E. coli strains of different origins. Similarities between the hly determinants of EPEC strains and the hly region of an uropathogenic strain were detected by DNA-hybridization. By this method hly genes of EPEC strains belonging to O-serogroups 114 and 126 were localized on the bacterial chromosome. The hly determinants of O26 strains were localized on 100 +/- 5 MD size conjugative plasmids. The hly plasmid pEO5 of the O26 strain C4115 was transferred by conjugation into an E. coli K12 recipient and found to be stable inherited. The hemolytic activity of the transconjugant was comparable to the wildtype O26 donor. The plasmid pEO5 was found to be different in size, compatibility and hemolysin expression from a number of described hemolysin-plasmids.