Detection of Salmonella enterica in food using two-step enrichment and real-time polymerase chain reaction.

AIMS

A new real-time polymerase chain reaction-based method was developed for the detection of Salmonella enterica in food.

METHODS AND RESULTS

The method consisted of a novel two-step enrichment involving overnight incubation in buffered peptone water and a 5-h subculture in Rappaport-Vassiliadis medium, lysis of bacterial cells and a Salmonella-specific 5'-nuclease real-time PCR with an exogenous internal amplification control. Because a two-step enrichment was used, the detection limit for dead S. enterica cells in artificially contaminated ice cream and salami samples was high at 10(7 )CFU (25 g)(-1), eliminating potential false-positive results. When the method was evaluated with a range of 100 naturally contaminated food samples, three positive samples were detected by both the real-time PCR-based method and by the standard microbiological method, according to EN ISO 6579. When the real-time PCR-based method was evaluated alongside the standard microbiological method according to EN ISO 6579 with 36 food samples artificially contaminated at a level of 10(0 )CFU (25 g)(-1), identical results were obtained from both methods.

CONCLUSIONS

The real-time PCR-based method involving a two-step enrichment produced equivalent results to EN ISO 6579 on the day after sample receipt.

SIGNIFICANCE AND IMPACT OF THE STUDY

The developed method is suitable for rapid detection of S. enterica in food.