Rapid, specific detection of Salmonella Enteritidis in pooled eggs by real-time PCR

An assay was developed for the specific detection of Salmonella Enteritidis in eggs with the use of an application of the fluorogenic 5' nuclease assay (TaqMan). In this assay, a segment of the gene sefA specific to Salmonella group D strains such as Salmonella Enteritidis was used. The amplification of the target gene products was monitored in real-time by incorporating a fluorescent dye-labeled gene-specific probe in the PCR reaction. This method correctly detected and distinguished Salmonella Enteritidis from nearly 50 of non-group D Salmonella and other non-Salmonella strains. Detection of the sefA gene was linear for DNA extracted from approximately 10(2) to 10(9) CFU/ml in phosphate-buffered saline and 10(3) to 10(8) CFU/ml in raw egg. In two trials, when applied to detection of Salmonella Enteritidis in homogenized egg pools and compared with conventional culture methods, the newly developed PCR method yielded a 100% correlation with results obtained by a conventional culture method. However, the PCR method required only 2 days, compared to the 5 days required by the culture method. The sensitivity of this assay was approximately less than 1 CFU/600 g of egg pool. The real-time PCR assay proved to be a rapid, highly sensitive test for detection and quantification of low concentrations of Salmonella Enteritidis in egg samples.