Characterization of Escherichia coli serogroups causing meningitis, sepsis and enteritis. II. Classification of Escherichia coli O78 strains by phage sensitivity, colicin type and antibiotic resistance.

Escherichia coli O78: K80 strains isolated from an outbreak of meningitis, sepsis and enteritis in infants, were compared with O78: K80 strains from sporadic cases of enteritis, healthy carriers and animals. The strains were uniform in antigenic structure and phage pattern but differed in colicinogenicity. The epidemic strains and calf-pathogenic cultures produced colicin V, the remaining isolates were characterized by other types of colicin or were not colicinogenic. Col V+ strains multiplied in the mouse peritoneal cavity more readily and killed the animals at significantly lower doses than did col V- strains. One half of antibiotic resistant O78: K80 strains carried R factor. The spread of R factor could be followed by phage restriction experiments.