title: Rapid detection of Listeria monocytogenes by real-time PCR in processed meat and dairy products.
abstract: The objectives of this study were to evaluate the detection of Listeria monocytogenes in different ready-to-eat foods using real-time PCR (RT-PCR). Various concentrations (10(0) to 10(5) CFU/ml) of L. monocytogenes ATCC 19115 were inoculated into ham, sausage, ground meat, processed milk, cheese, and infant formula. L. monocytogenes ATCC 19115 in the samples was then enumerated on Oxford agar, and DNA was extracted from the samples before and after incubation at 36°C for 4 h. A set of primers and hybridization probe designed in this study was then used to detect the pathogen. The standard curve was then prepared by plotting cycle threshold values for each dilution versus L. monocytogenes cell counts (log CFU). The specificity of the set of primers and hybridization probe was appropriate. A 4-h incubation at 36°C before DNA extraction produced optimum standard curves in comparison to the results for a 0-h incubation. Thus, a 4-h incubation at 36°C was applied for monitoring L. monocytogenes in collected food samples. To monitor L. monocytogenes in foods, 533 samples (ham, 129; sausage, 226; ground meat, 72; processed cheese, 54; processed milk, 42; and infant formula, 10) were collected from retail markets and from the step before pasteurization in plants. Of all 533 samples, 4 samples (0.8%) showed positive signals in RT-PCR. Two samples from hams (1.6%) and two samples from sausages (0.9%) were determined to be positive for L. monocytogenes at < 100 CFU/g. The results indicate that the RT-PCR detection method with the set of primers and hybridization probe designed in this study should be useful in monitoring for L. monocytogenes in processed meat and milk products.
authors.affiliation: Food Microbiology Division, Food Safety Evaluation Department, Ministry of Food and Drug Safety, Cheongwon 363-951, South Korea.
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Heo
authors.affiliation: Food Microbiology Division, Food Safety Evaluation Department, Ministry of Food and Drug Safety, Cheongwon 363-951, South Korea.
authors.forename: Bo Ra
authors.initials: BR
authors.lastname: Song
authors.affiliation: Agro-Livestock & Fishery Products Policy Division, Ministry of Food and Drug Safety, Cheongwon 363-951, South Korea.
authors.forename: Hyun Jung
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Livestock Products Standard Division, Ministry of Food and Drug Safety, Ministry of Food and Drug Safety, Cheongwon 363-951, South Korea.
authors.forename: Young Jo
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Veterinary Pharmaceutical Management Division, Animal and Plant Quarantine Agency, Anyang 430-757, South Korea.
authors.forename: Jin San
authors.initials: JS
authors.lastname: Moon
authors.affiliation: Veterinary Pharmaceutical Management Division, Animal and Plant Quarantine Agency, Anyang 430-757, South Korea.
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Wee
authors.affiliation: Research Center for Cell Fate Control and College of Pharmacy, Seoul 140-742, South Korea.
authors.forename: Jin-Seok
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Food and Nutrition, Sookmyung Women's University, Seoul 140-742, South Korea. yyoon@sookmyung.ac.kr.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Yoon
mesh_terms: D015169:Colony Count, Microbial; D017931:DNA Primers; D004269:DNA, Bacterial / Q000032:analysis*; D003611:Dairy Products / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008461:Meat Products / Q000382:microbiology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial