Detection of Salmonella in food, equivalent to ISO 6579, by a three-days polymerase chain reaction-based method

A method is presented for the detection of Salmonella in food, which produces definitive results on the third day after the sample collection. The method is equivalent to ISO 6579 in terms of the same detection limit of 100 cfu/25 g and 100% relative accuracy. The method involves pre-enrichment in buffered peptone water (16–20 h), two parallel selective enrichments in Rappaport–Vassiliadis and selenite–cystine medium, respectively (7 h), post-enrichment in Luria–Bertani medium (14–16 h), cell lysis by boiling in 1% Triton X-100, PCR using primers ST11, ST15 and a mimic internal control, and agarose gel electrophoresis. At the evaluation of the method on model food samples artificially contaminated with decimal dilutions of a Salmonella serotype Panama culture (cream cakes, ice cream, mayonnaise, meat products; 12 samples altogether), a detection limit of 100 cfu/25 g was determined. This detection limit was confirmed by the evaluation of the method on the mentioned model food samples artificially contaminated with reference materials containing on average 5 cfu of S. Panama. At the evaluation of the method on naturally contaminated food samples (cream cakes, ice cream, mayonnaise, egg melange, minced and separated meat, ham and salami; 44 samples altogether), identical results (9 positives) as with the reference method were obtained.