Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2002
Publication Date: 4/1/2003
Citation: GAST, R.K., HOLT, P.S., NASIR, M.S., JOLLEY, M.E., STONE, H.D. DETECTION OF SALMONELLA ENTERITIDIS IN INCUBATED POOLS OF EGG CONTENTS BY FLUORESCENCE POLARIZATION AND LATERAL FLOW IMMUNODIFFUSION. POULTRY SCIENCE. 2003. 82:687-690.
Interpretive Summary: Because humans can become infected with Salmonella enteritidis by consuming contaminated eggs, detecting this pathogen inside eggs is an important method for determining when laying flock pose a threat to public health. In most standard culturing methods for finding S. enteritidis cells inside eggs, the contents of a number of eggs are pooled together and incubated to allow small numbers of bacteria to grow to levels that can more easily be detected. In the present study, two innovative methods (fluorescence polarization and lateral flow immunodiffusion) were evaluated for their ability to detect S. enteritidis in incubated egg pools faster than standard culturing. Both rapid methods could only detect S. enteritidis in egg pools at levels of 107 cells per ml or higher. The rapid methods were less sensitive than culturing for detecting S. enteritidis, but they were consistently able to detect contamination when very small numbers of cells were added to egg pools and then incubated at 25 C for 72 hours.
Technical Abstract: Efficient detection of Salmonella enteritidis inside eggs is critical for determining whether individual commercial laying flocks present a risk to public health. In most standard bacteriological culturing protocols, an initial incubation step is necessary to allow the typically very small population of S. enteritidis cells in pools of egg contents to multiply to more easily detectable levels. The present study evaluated two rapid methods as alternatives to culturing for detecting S. enteritidis in incubated egg pools. Both fluorescence polarization and lateral flow immunodiffusion assays detected S. enteritidis in egg pools at levels of 107 cfu/ml or higher. Although the rapid assays were significantly less sensitive than culturing, they both were consistently able to detect contamination when pools of 10 eggs were inoculated with approximately 10 cfu of S. enteritidis and incubated for 72 hours at 25 C.