Comparison of an isothermal amplification and bioluminescence detection of DNA method and ISO 6579:2002 for the detection of Salmonella enterica serovars in retail meat samples.

The aim of the study was the comparative evaluation of an isothermal amplification and bioluminescence detection of DNA (IMBD) method and method ISO 6579:2002 for detection of Salmonella in retail meat products of unknown contamination status. A total of 200 meat samples were tested: 116 minced meat and meat preparations to be eaten cooked (52 chicken, 48 pork, and 16 beef samples) and 84 fresh meat samples (68 poultry and 16 pork). With one or both methods, 21 samples (10.5%) were positive for Salmonella enterica. Fifteen samples were positive with both methods (71.4% of all positive samples), two more samples (9.5%) were positive with the IMBD method only, and four samples (19.1%) were positive with the ISO method only. One ISO-positive sample was inhibited with the IMBD method. For the IMBD method, relative accuracy was 97.0% (95% confidence interval [CI], 93.6 to 98.9%), relative sensitivity was 78.9% (95% CI, 54.4 to 93.9%), and relative specificity was 98.9% (95% CI, 96.1 to 99.7%). Time to negative results was shorter with the IMBD method (20 to 24 h). Also, positive results were available in 20 to 24 h but should be confirmed using other methods (presumptive-positive results). Rapidity of response of the IMBD method gave us the opportunity to test the presumptive-positive samples by the most-probable-number (MPN) method, which was not performed for samples that were positive only with the ISO method because of likely microbial changes during the long storage period (5 to 7 days) at refrigeration temperature. Salmonella MPN values in naturally contaminated meat were low, at <0.3 to 2.1 MPN/g.