Comparison of PCR, Electrochemical Enzyme-Linked Immunosorbent Assays, and the Standard Culture Method for Detecting Salmonella in Meat Products

Abstract

An electrochemical enzyme-linked immunosorbent assay (ELISA) coupled with flow injection analysis (ELISA-FIA) and a PCR-based method using ST11 and ST15 primers for detecting salmonellae in meat were evaluated in comparison with the International Organization for Standardization (ISO) culture method. The methods were applied to experimentally contaminated and naturally contaminated meat samples. The results showed that both ELISA-FIA and PCR allowed detection of salmonella in a product contaminated with a low number of the microorganisms (1 to 10 salmonellae/25 g) after only 5 h of incubation of preenrichment broth, and they were just as effective as the ISO method.The incidence of foodborne infection by Salmonella continues to be an important problem in the United States (16) and in the European Community (4, 16).Raw and undercooked meat, eggs, milk, and especially poultry are the most commonly implicated vehicles of Salmonella spp. infection (10,15,16,20,24). For foods to be considered "salmonella free," European legislation requires that from 1 to 25 g be tested, depending on the type of food. The standard culture method (ISO 6579/2002) for detection of salmonella in food is rather sensitive and quite inexpensive, but it requires 4 to 5 days to generate results.Given that efforts to prevent salmonellosis must be applied at all phases of the food production chain, based on the Hazard Analysis Critical Control Point (HACCP) system (23), the methods for detecting salmonella need to be more rapid than the ISO method. To this end, new technologies have been used to develop rapid methods. Specifically, a number of antibodyantigen-based methods have been developed to detect Salmonella spp. or specific serotypes in a variety of food (3,8,13,18,21,25). Other authors developed immunoelectrochemical assays or piezoelectric flow injection analysis (FIA) biosensors to detect Salmonella enterica serotype Typhimurium (2, 7, 26). However, although these biosensors have the potential to provide direct label-free detection of bacteria, these piezoelectric FIA systems have a low level of sensitivity, and neither has been applied to food samples.Methods based on PCR for the detection of salmonella in food have also been developed (12,17,19).All of the above methods require that a preenrichment step be performed (5,9,14,18,22).The objective of the present study was to evaluate two rapid techniques for detection of salmonella: an electrochemical enzyme-linked immunosorbent assay (ELISA) coupled with FIA (ELISA-FIA) (6) and a PCR method using ST11 and ST15 primers (1).The experiments were first performed with experimentally contaminated samples to reduce and optimize the preenrichment times; the two methods were then applied to naturally contaminated meat samples, and the results were compared to those obtained with the International Organization for Standardization (ISO) method. MATERIALS AND METHODSThe experiments were performed on the following: (i) experimentally contaminated meat samples, to establish the minimum preenrichment...

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Foodborne bacterial pathogens recovered from contaminated shawarma meat in northern Jordan

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Salmonella in food surveillance: PCR, immunoassays, and other rapid detection and quantification methods

“…An enzyme-linked immunosorbent assay coupled with flow injection analysis (ELISA-FIA) was developed and compared with the ISO culture method for detecting salmonellae in meat samples (Croci, Delibato, Volpe, De Medici, & Palleschi, 2004). It was found that the ELISA-FIA had a detection limit of 1-10 salmonellae per 25 g food when a 5-h pre-enrichment step was employed.…”