Evaluation of real-time polymerase chain reaction coupled to immunomagnetic separation (rtPCR-IMS) as an alternative method for the routine detection of Salmonella spp. in beef in Mexico

Abstract

Salmonella is a pathogenic bacterium considered a threat to the food industry, its timely detection being relevant. The objective of the study was to evaluate the real-time polymerase chain reaction coupled to immunomagnetic separation (rtPCR-IMS) as an alternative method to the Official Mexican Standard (NOM-114-SSA1-1994) for the detection of Salmonella in beef. The parameters evaluated were limit of detection, sensitivity, specificity, selectivity (inclusivity and exclusivity) and degree of agreement between both methods for the detection of Salmonella in presumptive and artificially contaminated beef samples. The incidence of Salmonella in presumptive beef samples (n= 60) ranged from 20.0 to 21.6 % by both methods. In the inoculated samples (n= 60), the detection rate of Salmonella by rtPCR-IMS (93.3 %) and NOM-114-SSA1-1994 (98.3 %) showed a match of 56 occasions with a negative deviation. The comparison of rtPCR-IMS and NOM-114-SSA1-1994 in beef reported an accuracy of 98.3 %, sensitivity of 98.2 %, specificity of 100 % and selectivity of 100 %. The limit of detection for both methods was 1-5 CFU·25 g-1of beef. The statistical analysis indicates that the rtPCR-IMS is equivalent to the reference method for the detection of Salmonella in beef. These results warn of the high incidence of Salmonella in beef and propose rtPCR-IMS as an ideal and fast method for the control of Salmonella in the meat industry.