A COMPARISON OF IMMUNOMAGNETIC SEPARATION, DIRECT CULTURE AND POLYMERASE CHAIN-REACTION FOR THE DETECTION OF VEROCYTOTOXIN-PRODUCING ESCHERICHIA-COLI O157 IN HUMAN FECES

Verocytotoxin-producing Escherichia coli 0157 (0157 VTEC) has become w ell recognised as an important enteric pathogen. The number of organis ms present in environmental and clinical samples may be low and effort s have been made to increase the sensitivity of 0157 VTEC detection. I mmunomagnetic separation (IMS) has been shown to improve 0157 VTEC det ection in bovine faeces and food samples, A milk-borne outbreak of 015 7 VTEC infection allowed us to compare the isolation rates from human faeces by IMS, direct faecal culture on sorbitol-MacConkey agar and a PCR test for verotoxin gene carriage, Of 142 faecal samples examined, 20 were positive on both direct culture and IMS and a further 13 on IM S alone. Therefore, IMS increased the detection rate of individual cas es of 0157 VTEC infection and also compared web with PCR. We recommend IMS for use in routine diagnostic laboratories where a more sensitive method than direct faecal culture is required for 0157 VTEC isolation .