The growth of Salmonella enteritidis inoculated into the yolks of shell eggs from normal and seropositive hens was determined at various temperatures. All eggs were inoculated with approximately 1 colony-forming unit (CFU)/g of yolk. In eggs from normal hens, the organism multiplied with a generation time of 25 min, reaching a density of about 108 CFU/g in 12 h at 37°C. A generation time of 3.5 h was observed in eggs incubated at 15.5°C, a temperature frequently used for commercial storage of eggs. Cell density of >107 CFU/g was reached in 4 d at 15.5°C. No multiplication was observed in eggs incubated at 7°C for 94 d. When inoculated eggs from seropositive birds were incubated at 37°C, the organism multiplied with a generation time of 35 min, reaching a cell density of >106 CFU/g in 12 h. Raw egg white was detrimental to cells, reducing cell viability 50% in 4 h at 37°C. The limulus amoebocyte lysate test gave a positive reaction with whole liquid egg containing <103 CFU/g. A protocol is suggested for possible application of this test in epidemiological studies that screen grade A shell eggs for Salmonella contamination.
1Division of Microbiology, FDA, Cincinnati, OH 45226.
2Division of Microbiology, FDA, Washington, DC 20204.
3Cincinnati District Office, FDA, Cincinnati, OH 45202.