A biotyping scheme for Shiga-like (Vero) toxin-producing Escherichia coli O157 and a list of serological cross-reactions between O157 and other gram-negative bacteria

Abstract

In this study, 41 strains of E. coli O157 were investigated and divided into 4 serovars: O157:H7 (19 strains), O157:H- (20 strains), O157:H43 (1 strain) and O157:H45 (1 strain). However, a formation of SLT cytotoxins was only associated with the serovars O157:H7 and O157:H-. The strains of O157:H7 produced either SLT I and SLT II (the vast majority of 10 isolates), SLT II (7 isolates), or SLT II vhc human variant (2 isolates) which had been isolated in Germany for the first time. The majority of 16 strains of serovar O157:H- produced only the SLT II cytotoxin and 4 strains, both toxins, SLT I and SLT II. The pathogens were identified in connection with watery and bloody diarrhoea, with HUS and TTP sequelae. All age groups, in particular that of infants from 0 to 5 years, were affected by these infections. Ten strains (25.6%) out of a total of 39 SLT-producing strains were sorbitol-positive and not recognized on the sorbitol MacConkey plate during isolation. A scheme of 11 biotypes has been suggested for the biotyping of E. coli O157 and the antigenic relationships between O and OK antigens of E. coli O157 and those of other E. coli serogroups and other Gram-negative bacteria which were tested. An antigenic relationship was proved to exist between the O157 antigen and the twelve O antigens of other E. coli serogroups as well as between the O157 antigen and the antigens O:IB of Y. pseudotuberculosis, O:30 of Salmonella group (N) and O:9 of Y. enterocolitica.