Improved sensitivity and reproducibility of the PCR method for detection of Listeria spp. and L. monocytogenes in milk

Abstract

Listeria monocytogenes is a facultative intracellular Grampositive bacterium, ubiquitous in nature and capable of causing listeriosis in humans and animals. Conventional microbiological techniques and modern molecular approaches are currently used for the isolation and detection of L. monocytogenes in food samples. The aim of this study was to improve the sensitivity and reproducibility of PCR for the detection of Listeria spp. in milk. For that purpose milk samples were artificially inoculated with serial dilutions of L. monocytogenes 4b ATCC 19115 and L. innocua ATCC 33090. The results obtained on artificially contaminated milk samples indicated that incubation time and target genes have an influence on the sensitivity of PCR detection. The best results were obtained after 24 h of preenrichment, with primers complementary to the hlyA gene, when it was possible to detect 1 CFU/mL of Listeria spp.