Comparison of four different methods for Salmonella detection in fecal samples of porcine origin

Salmonella detection in poultry meat and meat products by the Vitek immunodiagnostic assay system easy Salmonella method, a LightCycler polymerase chain reaction system, and the International Organization for Standardization method 6579

This study was conducted to evaluate the capability of the Vitek immunodiagnostic assay system easy Salmonella (VIDAS ESLM) method and a specific real-time PCR system (LightCycler, LCPCR) to complement the International Organization for Standardization Method 6579 (ISO) in detecting Salmonella from a total of 105 naturally contaminated samples comprised of poultry meat and poultry meat products. The detection limit of ISO and LCPCR was 9 cfu/mL for both poultry meat and poultry meat products, whereas that of VIDAS ESLM with both sample types was determined to be 90 cfu/mL. Twelve (33.33%), 11 (30.55%), and 18 (50.00%) out of 36 poultry meat samples were positive for Salmonella by ISO, VIDAS ESLM, and LCPCR, respectively. Salmonella detection rates from poultry meat products were 5.80% for ISO and 8.69% for LCPCR, whereas none of these products tested positive by VIDAS ESLM. In poultry meat samples, VIDAS ESLM and LCPCR detection results were in substantial agreement with ISO, with the relative accuracy, sensitivity, and specificity rates of 97.2, 91.7, and 100%, respectively, for VIDAS ESLM and 83.3, 100, and 75%, respectively, for LCPCR. This is the first report on the evaluation of both VIDAS ESLM and LCPCR to complement ISO for the rapid detection of Salmonella in poultry meat and meat products. We determined that both VIDAS ESLM and LCPCR have the potential to complement the ISO standard culture method in the rapid screening of Salmonella from naturally contaminated poultry meats. For the poultry meat products, VIDAS ESLM and LCPCR can be used for rapid primary screening, and they should be complemented absolutely by ISO. Although LCPCR can preferentially be used for initial screening poultry meat products, the results should definitely be confirmed by ISO. Also, the VIDAS ESLM did not seem to be a suitable method for detecting Salmonella in poultry meat products.

Comparison of Five Culture Methods for Salmonella Isolation from Swine Fecal Samples of Known Infection Status

The current study was conducted to evaluate 5 bacteriologic culture methods (methods 1, 2, 3, 4, and 5) for recovery of Salmonella enterica from swine feces, both for sensitivity of detection (ability to recover Salmonella from a positive sample) and for specificity (not to inadvertently identify an organism as a Salmonella species in a negative sample). Fifty-six negative samples and 46 positive samples were processed using each of the 5 methods, which differed primarily in the combinations of enrichment media used. All negative samples were negative for Salmonella when cultured by all 5 methods (100% specificity). Two of the methods (methods 1 and 4) resulted in the recovery of significantly less ( P < 0.05) Salmonella when compared with the remaining 3 methods (methods 2, 3, and 5). No one method was successful in recovering Salmonella from all positive samples, although recovery with method 2 was statistically similar to the total number of positive samples analyzed (42 vs. 46 Salmonella-positive samples, P > 0.05). This study shows that culture methods differ significantly in their performance regarding the isolation of Salmonella from swine fecal samples.

Comparison of culture, ELISA and PCR techniques for salmonella detection in faecal samples for cattle, pig and poultry

BACKGROUND

Performances of different salmonella detection methods were evaluated by applying them to of artificially contaminated faecal specimens from cattle, pigs and poultry. The NMKL71 method, being the standard reference method for detection of salmonella in the official Swedish control program, was compared with the proposed ISO method using MSRV-selective enrichment for culturing, and also with three commercial ELISA- based systems, Bioline Selecta, Bioline Optima and Vidas, a commercial PCR-based method, BAX system, and three different strategies using PCR detection using a non-commercial PCR system.

RESULTS

Altogether, 391 samples were tested, and the overall results clearly indicate that, when faeces from all animal species and all serotypes were included, the MSRV performed best, with a calculated accuracy of 99% and a calculated sensitivity of 98%. The second most sensitive and specific method was the BAX system, using the modified enrichment protocol as recommended by the manufacturer for faecal samples. However, this protocol includes one additional day of work, as compared with the standard procedure for food sample analysis by the same method. The different strategies for salmonella detection using non-commercial PCR showed a sensitivity and specificity in the same range as the BAX method; furthermore, results were obtained more quickly. The various commercial ELISA methods and the NMKL method showed the poorest performance of the methods included in the study, and were closely dependent on the origin of the faeces used and on which salmonella strain was to be detected.

CONCLUSION

The study showed that the sensitivity of the different methods depended to a great extent on the origin of the faecal matrices and the salmonella strains used to "spike" the samples.