Detection of Salmonella enteritidis in Experimentally Infected Laying Hens by Culturing Pools of Egg Contents

Two experiments were conducted to determine whether Salmonella enteritidis could be detected efficiently in pooled samples of the contents of eggs laid by experimentally infected hens. In Experiment 1, groups of laying hens were orally inoculated with either 10(4) or 10(6) S. enteritidis cells. In Experiment 2, one-third of the hens in each group were orally inoculated with 10(6) S. enteritidis cells. At 2 wk postinoculation, culturing egg pools yielded positive results at frequencies similar to those obtained by culturing fecal samples, culturing internal organs, or testing for specific serum antibodies. Culturing fecal samples detected a higher percentage of exposed hens than egg pool culturing at 1 and 3 wk, and serum antibody tests were superior at 3 and 4 wk. In Experiment 1, more than 46% of the hens inoculated with 10(6) S. enteritidis cells laid at least one contaminated egg during the 2nd wk postinoculation. In Experiment 2, over 34% of the hens produced at least one contaminated egg during the 2nd wk postinoculation, but very few contaminated egg pools were identified during the 3rd and 4th wk. Bacteriological culturing of pooled egg contents for S. enteritidis, therefore, can apparently provide an effective method for assessing the potential public health threat posed by a flock.