Reducing time in the analysis of Listeria monocytogenes in meat, dairy and vegetable products. 2014

David Rodriguez-Lazaro, and Patricia Gonzalez-García, and Antonietta Gattuso, and Monica Virginia Gianfranceschi, and Marta Hernandez
Subdirección de Investigación y Tecnología, Instituto Tecnológico Agrario de Castilla y León (ITACyL), Carretera de Burgos Km, 119, Valladolid, Spain; Microbiology Section, Faculty of Sciences, University of Burgos, Plaza Misael Bauñuelos s/n, 9001 Burgos, Spain. Electronic address: rodlazda@gmail.com.

The microbiological standard for detection of Listeria monocytogenes relies on several cultural steps and requires 7 days for final confirmation, and due to food distribution and market demands, there is a prevailing need for an alternative methodology for its detection. The aim of this study was to compare different detection strategies based on real-time PCR (RTi-PCR) for a rapid and sensitive detection in an ample range of food products: raw pork and poultry meat, raw sheep milk cured cheese, and ready to eat lettuce salad. Four parameters were evaluated to reduce the time and cost for final results: the initial sample size (25 and 50 g), the dilution of the sample (1:3; 1:5 and 1:10 dilutions in Half Fraser broth), the incubation times (6, 10 and 24h) and the bacterial DNA extraction (simple boiling of the culture after washing the bacterial pellet, the use of the Chelex resin, and a commercial silica column. The results obtained demonstrate that a combination of an incubation in Half-Fraser for 24h of a 1:10 diluted-25 g-sample coupled to a DNA extraction using a commercial silica column and a real-time PCR assay detected down to 2-4 L. monocytogenes CFU per sample in less than 27 h in different types of food products. This RTi-PCR-based method is fully compatible with the ISO standard, providing results more rapidly and cost-effectively. The results were confirmed in a large number of naturally contaminated food samples with at least the same analytical performance as the reference method.

UI MeSH Term Description Entries
D008089 Listeria monocytogenes A species of gram-positive, rod-shaped bacteria widely distributed in nature. It has been isolated from sewage, soil, silage, and from feces of healthy animals and man. Infection with this bacterium leads to encephalitis, meningitis, endocarditis, and abortion.
D008460 Meat The edible portions of any animal used for food including cattle, swine, goats/sheep, poultry, fish, shellfish, and game. Meats
D011200 Poultry Domesticated birds raised for food. It typically includes CHICKENS; TURKEYS, DUCKS; GEESE; and others. Fowls, Domestic,Domestic Fowl,Domestic Fowls,Fowl, Domestic,Poultries
D002611 Cheese A nutritious food consisting primarily of the curd or the semisolid substance formed when milk coagulates. Cheeses
D004269 DNA, Bacterial Deoxyribonucleic acid that makes up the genetic material of bacteria. Bacterial DNA
D005516 Food Microbiology The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept. Microbiology, Food
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012680 Sensitivity and Specificity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed) Specificity,Sensitivity,Specificity and Sensitivity
D013552 Swine Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA). Phacochoerus,Pigs,Suidae,Warthogs,Wart Hogs,Hog, Wart,Hogs, Wart,Wart Hog
D013995 Time The dimension of the physical universe which, at a given place, orders the sequence of events. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Effects, Long-Term,Effects, Longterm,Long-Term Effects,Longterm Effects,Effect, Long-Term,Effect, Longterm,Effects, Long Term,Long Term Effects,Long-Term Effect,Longterm Effect

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