Detection and Enumeration of Salmonella enteritidis in Fresh and Stored Eggs Laid by Experimentally Infected Hens

Abstract

Laying hens were orally inoculated with a phage type 13a strain of Salmonella enteritidis (SE). Eggs laid by the infected hens were collected daily between the 4th and 14th d postinoculation and randomly allocated into three groups. One group of eggs was sampled on the day of collection, one group was held for 7 d at 7.2°C before sampling, and one group was held for 7 d at 25°C before sampling. The frequency and level of detectable contamination of egg contents by SE were determined for each group. Only 3% of the freshly laid eggs and 4% of the eggs held for 7 d at refrigerator temperature were identified as having SE-contaminated contents, whereas SE was isolated from the contents of 16% of eggs held for 7 d at room temperature. Enumeration of SE in contaminated eggs indicated greater numbers of SE in eggs held for 7 d at 25°C than in eggs from the other two groups, although most contaminated eggs in all three groups contained relatively small numbers of SE (generally less than 10/ml and rarely exceeding 100/ml).