Evaluation of the polymerase chain reaction for the detection of Salmonella enteritidis in experimentally inoculated eggs and eggs from experimentally challenged hens

Current recommendations for identification of Salmonella enteritidis (SE)-contaminated eggs, as outlined by the USDA SE Task Force, require the combination of yolk and albumen from several eggs for room-temperature enrichment for 3 days prior to culture on solid medium. We have previously reported the development of a technique involving enzymatic digestion and chemical reduction of pools of egg albumen allowing for the concentration of low numbers of SE by centrifugation. This technique allowed for detection of Salmonella with sensitivity comparable to conventional culture. Importantly, this technique allowed presumptive identification of SE at least 48 h sooner than conventional culture. We presently describe the use of this technique for the concentration of low numbers of SE in albumen pools for detection by the polymerase chain reaction (PCR). Three experiments performed with experimentally inoculated eggs indicated the PCR to be similar in sensitivity to the room temperature culture procedure for the detection of SE. Additionally, 5 experiments were performed in which hens were experimentally challenged with SE, and eggs were collected at selected times postchallenge. While few positive egg pools were detected by either method, data suggested that the PCR did not falsely identify positive eggs. These experiments provide preliminary evidence that the PCR is comparably sensitive to the room-temperature culture technique, while providing pre sumptive identification of SE 72 h sooner than conventional culture.