title: Simultaneous detection of Listeria monocytogenes and Salmonella spp. in dairy products using real time PCR-melt curve analysis.
abstract: The present investigation reports development of post real time PCR (RTi-PCR) - melt curve analysis for simultaneous detection of Listeria monocytogenes and Salmonella spp. The optimal Sybr Green I (SG-I) concentration of 1.6 μM resulted in two specific peaks with melting temperature (Tm) of 79.90 ± 0.39 °C and 86.29 ± 0.13 °C for L. monocytogenes and Salmonella spp respectively. The detection sensitivity of the assay in reconstituted non-fat dried milk (NFDM; 11%) spiked with the target pathogens at different levels was 3 log cfu per ml of each pathogen. However, the sensitivity was improved up to 1 log cfu per ml by including pre-enrichment step of 6 h. On application of assay on 60 market samples, one sample each of raw milk and ice cream was detected positive for L. monocytogenes and Salmonella spp. Assay was quite specific as no cross reactivity with non target cultures could be observed. The developed assay can find valuable application in monitoring dairy products for the presence of L. monocytogenes and Salmonella spp. to ensure their microbiological quality and safety.
authors.affiliation: Molecular Biology Unit, Dairy Microbiology Division, National Dairy Research Institute, Karnal, 132001 Haryana India ; Product and Process Development Group, CALF Building, National Dairy Development Board, Anand, 388001 Gujarat India.
authors.forename: Jitender
authors.initials: J
authors.lastname: Singh
authors.forename: Virender K
authors.initials: VK
authors.lastname: Batish
authors.forename: Sunita
authors.initials: S
authors.lastname: Grover
keywords: Dairy products; Listeria monocytogenes; Melt curve analysis; Real time PCR; Salmonella spp