DETECTION OF ESCHERICHIA-COLI SEROGROUP O157 IN FOODS BY IMMUNOMAGNETIC SEPARATION (IMS)

Recovery rates of E. coli O157:H7 strain B 2482, artificially inoculat ed into ground beef samples, were established with and without using D ynabeads(R) anti-E. coli O157 for immunomagnetic separation (IMS) unde r different methodical conditions. Independent of the level of contami nation the IMS was superior to the control procedure; reliable results could be observed already after a 6 hours incubation period. The best results were obtained using simultaneously two enrichment media (tryp tic soy broth [TSB] and brilliant green lactose bile broth [BRILA]) wh ich were screened for E. coli O157 by IMS after 6 and 24 hours, follow ed by a subcultivation on two selective media (hemorrhagic colitis aga r [HC] and cefixime tellurite sorbitol MacConkey agar [CT-SMAC]). The detection of very low E. coli O157-concentrations - as typically found in foodstuffs - after only 24 hours was frequently possible. The resu lts indicate that IMS is a sensitive, convenient and rapid method for the isolation of E. coli O157 in foods.