EVALUATION OF THE VIDAS METHODOLOGY FOR DETECTION OF ESCHERICHIA-COLIO157 IN FOOD SAMPLES

An automated enzyme-linked fluorescence immunoassay (ELFA), the VIDAS E. coli O157 method, was compared with immunomagnetic separation (IMS) followed by culture on cefixime tellurite sorbitol MacConkey agar (CT -SMAC) for detecting Escherichia coli O157 in artificially and natural ly contaminated food samples including raw milk cheeses, poultry, raw sausages, and ground beef retail samples. Confirmation of the samples positive according to the ELFA was performed by use of an automated im munoconcentration system, VIDAS ICE, which allows selective capture an d release of target organisms. A total of 496 retail food samples were examined. Seventeen food samples gave positive values with the ELFA m ethod, and among them 9 food samples were confirmed by the ICE method. Eight were shown to contain sorbitol-positive, O157-positive, H7-nega tive, motile, non-verotoxin-producing E. coli. The ninth positive samp le contained an O157-positive, H7-negative, sorbitol-negative, non-ver otoxin-producing E, coli. The IMS technique only allowed confirmation of this sorbitol-negative, non-verotoxin-producing E, coli O157.