Culture-based detection is still considered as the standard way for detection of Salmonella in foods, although molecular methods, such as viability PCR (vPCR), have been introduced to overcome some disadvantages of traditional culture methods. Despite the success of the vPCR methodology, the problem of false-positive results is a major drawback, especially when applied to environmental samples, hindering the interpretation of the results. To improve the efficiency of vPCR, many approaches have been introduced by several authors during the last years. In the present work, the combination of PEMAX dye, double tube change, and double photo-activation step was established as a strategy to improve vPCR protocol. By combining these approaches, we developed an improved sample treatment protocol able to neutralize DNA signals of up to 5.0×10 7 dead cells/sample from both pure culture and artificially contaminated food samples. Our results indicate that vPCR can work reliable and has a potential for high throughput detection of live Salmonella cells in food samples, minimizing false-positive signals.

Salmonella enterica subspecies enterica serovars Enteritidis and Typhimurium are important causes of foodborne illness. Methods for simultaneous detection of these serovars may contribute for the adoption of measures to prevent these diseases. The polymerase chain reaction to detect individually or simultaneously the serovars Enteritidis and Typhimurium in foods have been standardized; however, the majority of assays employ the fliC gene as a target for detection of serovar Typhimurium. The detection of these sorovars in a few hours allows the food supply chain to take appropriate measures to prevent the distribution of contaminated food. The aim of this study was to develop a new multiplex PCR (mPCR) for the simultaneous detection and differentiation of Salmonella spp., S. Enteritidis and S. Typhimurium in chicken meat. The mPCR assays showed high specificity and differentiated S. Typhimurium from 22 Salmonella serovars tested, including S. Kentucky, showing that it's an alternative to reduce the time required to obtain presumptive positive results. PRACTICAL APPLICATIONSThe fliC gene used as target for the detection of serovar Typhimurium is questionable as it has also been described for S. Kentucky. The amplification of STM4492 gene in this study, instead of fliC gene, exhibited high specificity to detect S. Typhimurium. The developed mPCR is an efficient means for the simultaneous detection and differentiation of Salmonella spp., S. Enteritidis and S. Typhimurium in chicken meat after 24 h of enrichment. The mPCR has the potential to be used in routine diagnostic laboratories to obtain presumptive positive results and for identification of Enteritidis and Typhimurium strains isolated by the conventional method. bs_bs_banner Journal of Food Safety ISSN 1745-4565

The control of Salmonella spp. and Campylobacter spp. in chicken meat is essential for avoiding sanitary barriers and preventing human disease. The aim of this study was to develop a multiplex polymerase chain reaction assay (mPCR) for the rapid detection of these bacteria in raw chicken meat. The mPCR was developed using the Styinva‐JHO‐Right and Styinva‐JHO‐Left primers (specific for Salmonella spp.) and the OT1559 and 18‐1 primers (specific for Campylobacter spp.). The specificity of the assay was 100% and it was able to detect 102 cfu/mL of Campylobacter spp. after the selective enrichment and 1 cfu/mL of Salmonella spp. after nonselective enrichment. Fifty raw chicken meat samples were analyzed; 4% were contaminated with Salmonella spp. and 56% with Campylobacter spp. The results obtained using mPCR were confirmed by conventional culturing methods. The developed mPCR method is a relatively inexpensive and efficient means to detect these bacteria after 24 h of enrichment. PRACTICAL APPLICATIONS The developed multiplex polymerase chain reaction method (mPCR) is a relatively inexpensive and efficient means to detect Salmonella spp. and Campylobacter spp. in chicken meat after 24 h of enrichment. The detection of these pathogens in a few hours allows the food supply chain to take appropriate measures quickly to prevent the distribution of contaminated food. Rapid and simultaneous detection of these bacteria in chicken meat can assist in the implementation of the preventive measures that can reduce contamination, which is very useful for Brazil, the third largest producer of chicken meat and the largest exporter of this product. Moreover, the developed mPCR may speed up the identification of suspected colonies of those bacteria on the selective media used in conventional culture methods.

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