Detection of Salmonella in food over 30 h using enrichment and polymerase chain reaction

A 30-h method for the detection of Salmonella spp. in food was developed. The method involved preenrichment in buffered peptone water for 6-8 h, immunomagnetic separation (IMS) using Dynabeads(R) anti-Salmonella, selective enrichment in Rappaport-Vassiliadis broth for 16-18 h, lysis of bacterial cells in sodium dodecylsulfate and NaOH solution at 95 degrees C, and the polymerase chain reaction (PCR) using primers ST11 and ST15. The detection limit of the method was 10 degrees cfu 25g(-1), as determined by the analysis of food samples artificially contaminated with S. enteritidis. When the reference material containing on average 5 cfu of S, panama was used for the artificial contamination, 3 out of 22 food samples were found to be false-negative. When the method was evaluated in comparison with the standard ISO 6579 method on 42 possibly naturally-contaminated food samples, one sample was found positive by the 30-h method, one sample was found positive by the lSO-method, and two samples were found positive by both methods. The developed method proved rapid, but produced a non-zero level of false-negative results. (C) 1999 Academic Press.