Incubation of egg contents pools at an elevated temperature (42 degrees C) does not improve the rapid detection of Salmonella enteritidis phage type 14b.
Detecting internal Salmonella Enteritidis (SE) contamination in eggs is essential for protecting public health. Pooling together > or = 10 eggs for sampling allows many eggs to be screened for contamination, but such pools must be incubated (usually at 25 to 37 degrees 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 degrees 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 degrees C. Incubation of contaminated egg pools at 42 degrees C resulted in significantly higher SE levels after 6, 8, 10, and 12 h. However, incubation at 42 degrees C could only generate a mean log SE concentration of 4.21 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 degrees C.
Gast
Richard K
RK
US Department of Agriculture, Agricultural Research Service, Southeast Poultry Research Laboratory, Athens, Georgia 30605, USA. rgast@seprl.usda.gov
Holt
Peter S
PS
D000818:Animals; D015169:Colony Count, Microbial; D004531:Eggs / Q000382:microbiology / Q000821:virology*; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D005779:Immunodiffusion / Q000379:methods; D012483:Salmonella Phages / Q000302:isolation & purification*; D012477:Salmonella enteritidis / Q000254:growth & development*; D013696:Temperature; D013997:Time Factors