A COMPARISON OF IMMUNOMAGNETIC SEPARATION AND DIRECT CULTURE FOR THE ISOLATION OF VEROCYTOTOXIN-PRODUCING ESCHERICHIA-COLI O157 FROM CASES OF BLOODY DIARRHEA, NON-BLOODY DIARRHEA AND ASYMPTOMATIC CONTACTS

Enrichment culture in modified buffered peptone water followed by immu nomagnetic separation (IMS) with magnetic beads coated with an antibod y against Escherichia coli O157 was compared with direct culture on ce fixime rhamnose sorbitol MacConkey agar (CR-SMAC) and cefixime telluri te sorbitol MacConkey agar (CT-SMAC) for the isolation of E. coli O157 from human faeces. In total, 690 samples were examined; E. coli O157 was isolated from 25 samples by IMS but from only 15 and 12 by direct culture on CT-SMAC and CR-SMAC, respectively, The difference in sensit ivity of detection was at its most marked on screening repeat faecal s amples from known cases and samples from asymptomatic contacts, when o f 12 strains of E. coli O157 isolated by IMS, only five were isolated by direct culture, IMS is a sensitive and simple technique for the iso lation of E. coli O157 from human faecal samples and should prove usef ul in elucidating further the epidemiology of this micro-organism.