Screening of food raw materials for the presence of Shiga toxin‐producing Escherichia coli O91:H21

Aims: To provide information on the prevalence and detection, in foods, of Shiga toxin‐producing Escherichia coli (STEC) O91:H21. Methods and Results: Seven hundred fifteen minced beef meats and 205 raw milk samples were analysed by stx‐specific PCR‐ELISA. Samples positive for stx were subsequently tested for the presence of wzy‐O91, fliC‐H21 and the adhesin‐encoding gene saa. For minced meat, 16 (2·2%) and 11 (1·5%) samples were found positive for (stx, wzy‐O91, fliC‐H21) and (stx, wzy‐O91, fliC‐H21, saa) combinations, respectively. For raw milk, seven (3·4%) samples were found positive for the (stx, wzy‐O91, fliC‐H21) combination but none of these contained saa. Two STEC O91:H21 saa‐positive strains and three STEC O91 H21– and saa‐negative strains were isolated by colony hybridization. Conclusions: A low prevalence of potentially pathogenic STEC O91:H21 in food products was found using a combination of PCR assays targeting stx, wzy‐O91, fliC‐H21 and saa. Significance and Impact of the Study: The PCR‐based approach described here represents a valuable method for rapid screening of food samples contaminated by STEC O91:H21.