Evaluation of DAS™ kits for the detection of food-borne pathogens in chicken- and meat-based street-vended foods

Abstract

The PCR-based method has gained acceptability as an alternative method for assessing the microbial safety of foods. In this study, the performance of PCR-based DNA Amplification System™ (DAS™) detection kits, namely, E. coli DAS™, S. aureus DAS™, E. coli O157:H7 DAS™ and Salmonella DAS™, were compared with reference methods in detecting the pathogens Escherichia coli, Staphylococcus aureus, E. coli O157:H7 and Salmonella spp. in 130 naturally- and artificially-contaminated chicken and meat-based grilled and fried street food samples. E. coli DAS™ displayed very good agreement with the reference method with a kappa value of 0.92 in chicken-based samples. S. aureus DAS™ also demonstrated very good agreement with the same kappa value of 0.92 but in meat-based samples. On the other hand, E. coli O157:H7 DAS™ and Salmonella DAS™ exhibited lower kappa values ranging from 0.67 to 0.76 in both food types. E. coli DAS™ obtained a high relative accuracy of 96% in chicken-based samples. S. aureus DAS™ also obtained a similar relative accuracy value of 96% but in meat-based samples. In terms of relative sensitivity, E. coli DAS™ and E. coli O157:H7 DAS™ showed high values of 96% and 95%, respectively, in chicken-based samples. Furthermore, E. coli DAS™, S. aureus DAS™ and Salmonella DAS™ demonstrated high relative specificities of 97%, 100% and 96% in chicken-, chicken-meat and meat-based samples, respectively. The performance of these kits was found to vary with food matrix, enrichment and cell-lysing procedures. Inclusion of internal amplification control, using more effective cell-lysing and enrichment procedures are suggested to enhance the overall performance of the kits.