Improved detection of Campylobacter jejuni, Listeria monocytogenes and Salmonella Typhimurium from raw meat products using conventional and newly developed TaqMan assays

Abstract

The most frequent bacteria contaminating raw meat samples from local retail outlets were determined. Comparison was made between conventional culture method (BIOLOG) and newly developed PCR assays performed on bacterial isolates (PCR-C), directly on enriched broths (Direct PCR-E) or on DNA extracted from enriched broths (PCR-E) of Campylobacter jejuni, Listeria monocytogenes and Salmonella Typhimurium. Among 150 meat samples (chicken, pork, turkey and beef) tested, Campylobacter, Proteus, Listeria and Salmonella were detected in 27.0, 25.0, 19.0 and 3.3%, respectively, by using BIOLOG. Among 150 samples analyzed, the frequency of detection for C. jejuni, L. monocytogenes and S. Typhimurium were 8.0, 2.7 and 2.0% by both the BIOLOG and PCR-C assays. PCR-C and BIOLOG detected the same number of positive samples, 12 for C. jejuni, 3 for S. Typhimurium, however from the total 4 L. monocytogenes, only 3 were isolated correctly by BIOLOG. Both Direct PCR-E and PCR-E detected 13, 2 and 1 positive samples for C. jejuni, S. Typhimurium and L. monocytogenes, respectively. TaqMan PCR assay on enriched broths produced the most rapid and inhibition-free results compared with Direct PCR-E and PCR-C. The PCRbased methods provided results more rapidly (1-2 days versus 6-7 days) and therefore are recommended for improved detection of these pathogens.