Incubation of Egg Contents Pools at an Elevated Temperature (42°C) Does Not Improve the Rapid Detection of Salmonella Enteritidis Phage Type 14b

Abstract

Detecting internal Salmonella Enteritidis (SE) contamination in eggs is essential for protecting public health. Pooling together ≥10 eggs for sampling allows many eggs to be screened for contamination, but such pools must be incubated (usually at 25 to 37°C) to permit small numbers of SE to multiply before further testing. The present study determined whether incubating egg contents pools at an elevated temperature (42°C) could increase the rate of multiplication of a phage type 14b strain of SE sufficiently to support the detection of contamination by a rapid lateral flow immunodiffusion method within a single day. Pools of 10 eggs were contaminated with approximately 10 CFU of SE, supplemented with concentrated broth enrichment medium, and incubated at either 37 or 42°C. Incubation of contaminated egg pools at 42°C resulted in significantly higher SE levels after 6, 8, 10, and 12 h. However, incubation at 42°C could only generate a mean log SE concentration of4.21 CFU/ml within a single working day (8 h), inadequate to support efficient detection by most rapid assays. Detection of SE contamination in egg pools by a rapid lateral flow immunodiffusion test was not achieved at a high frequency until 12 h of incubation at 42°C.