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. T he method involved preenrichment in buffered peptone water for 6-8 h, immun omagnetic separation (IMS) using Dynabeads(R) anti-Salmonella, selective en richment in Rappaport-Vassiliadis broth for 16-18 h, lysis of bacterial cel ls in sodium dodecylsulfate and NaOH solution at 95 degrees C, and the poly merase chain reaction (PCR) using primers ST11 and ST15. The detection limi t of the method was 10 degrees cfu 25g(-1), as determined by the analysis o f food samples artificially contaminated with S. enteritidis. When the refe rence material containing on average 5 cfu of S, panama was used for the ar tificial contamination, 3 out of 22 food samples were found to be false-neg ative. When the method was evaluated in comparison with the standard ISO 65 79 method on 42 possibly naturally-contaminated food samples, one sample wa s found positive by the 30-h method, one sample was found positive by the l SO-method, and two samples were found positive by both methods. The develop ed method proved rapid, but produced a non-zero level of false-negative res ults. (C) 1999 Academic Press.