Supplementing Pools of Egg Contents with Broth Culture Media To Improve Rapid Detection of Salmonella enteritidis

Abstract

Culturing egg contents to detect Salmonella enteritidis (SE) has become an important tool for identifying infected laying flocks and thereby reducing the transmission of SE to humans by contaminated eggs. The present study evaluated the efficacy of supplementing incubating egg pools with selective and nonselective enrichment broth media (prepared at higher than usual concentrations) for rapidly isolating SE by a direct plating culture method. When 100-ml pools of liquid whole egg from a mixture of 60 egg contents were contaminated with approximately 10 SE cells each, supplementation with ferrous sulfate or with concentrates of either tryptone soya broth or Rappaport-Vassiliadis broth significantly improved SE recovery. When 100-ml egg-contents pools were contaminated with approximately 2 SE cells each, the addition of concentrated tryptone soya broth to incubating egg pools resulted in significantly better SE recovery than did iron supplementation. Efficient presumptive detection of very low incidences and levels of SE contamination by direct plating was thus accomplished in a total of 48 h by adding concentrated tryptone soya broth to incubating egg pools.