Validated PCR assay for the routine detection of Salmonella in food.
We developed a rapid and reliable PCR assay with genus-specific primers for the detection of Salmonella in food samples. With these primers, no primer-specific amplicons were detected when challenged with cultures of microorganisms other than salmonellae, and positive results, i.e., Salmonella-specific bands, were obtained with pure cultures of all 125 Salmonella isolates tested, which represented 100 serovars. The PCR assay was optimized using both pure cultures and artificially inoculated food samples. The assay results were compared with those of the Australian standard culture methods, using more than 500 "naturally" contaminated food samples, over a period of 9 years. Food samples were subjected to nonselective preenrichment in buffered peptone water followed by selective enrichment in Rappaport Vassiliadis (RV) broth and mannitol selenite cystine (MSC) broth. A simple sample preparation method was developed based on concentrating bacterial cells from 1 ml of RV or MSC broths. The PCR results were in perfect agreement with the results of the standard culture methods; no false-positive or false-negative results were obtained. However, the PCR assay was extremely rapid, and results could be obtained within 4 h of testing of enrichment broths.
Institute of Clinical Pathology and Medical Research, Division of Analytical Laboratories, Western Sydney Area Health Services, Lidcombe, New South Wales, Australia. nbansal@dal.wsahs.nsw.gov.au
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Bansal
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Gray
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McDonell
D001315:Australia; D015169:Colony Count, Microbial / Q000379:methods; D003257:Consumer Product Safety; D017931:DNA Primers; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D012475:Salmonella / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013997:Time Factors
D017931:DNA Primers