VIRULENCE PROPERTIES OF ESCHERICHIA-COLI STRAINS BELONGING TO SEROGROUPS O26, O55, O111 AND O128 ISOLATED IN THE UNITED-KINGDOM IN 1991 FROM PATIENTS WITH DIARRHEA

Some strains of Escherichia coli belonging to serogroups O26, O55, O11 1 or O128 produce Vero cytotoxin (VT). These serogroups, are included in the range of enteropathogenic E. coli (EPEC) serogroups for which c ommercial antisera are available. In an attempt to obtain information on VT-producing strains other than those of serogroup O157, 122 strain s belonging to these four serogroups and isolated in 1991 from patient s with diarrhoea in the United Kingdom were tested for hybridization w ith VT probes. Only 18 of the 122 strains were VT-positive and these w ere O26 or O128. However 90 strains hybridized with the E. coli attach ing and effacing (eae) probe (including 14 VT-positive strains) and 17 with the enteroaggregative E. coli (EAggEC) probe. For 78 eae-positiv e and 9 EAggEC-positive strains, tissue culture tests correlated with the probe results as the strains gave, respectively, either localized adhesion and a positive fluorescent-actin staining test or a character istic aggregative attachment. A total of 111 of the 122 strains belong ing to serogroups O26, O55, O111 or O128 possessed properties that may be associated with the ability to cause human diarrhoeal disease, and similar studies are needed on strains from the other classical EPEC s erogroups.