Deposition of phage type 4 and 13a Salmonella enteritidis strains in the yolk and albumen of eggs laid by experimentally infected hens

Because egg yolk and albumen differ substantially in their abilities to sup port bacterial growth, the initial level and location of Salmonella enterit idis deposition are critical for determining whether proposed standards for refrigerating eggs are likely to protect public health by preventing exten sive microbial multiplication. In the present study, three groups of laying hens were infected with oral doses of approximately 10 degrees cells of di fferent S. enteritidis strains (two were phage type 4 and one was phage typ e 13a) in two replicate trials. For all three S. enteritidis strains, the i ncidence of yolk contamination (approximately 2.5% overall) was significant ly greater than the incidence of albumen contamination (approximately 0.5% overall). The phage type 13a strain was less often isolated from fecal samp les at 2 wk post-inoculation than were the phage type 4 strains, but no sig nificant differences between strains were observed in the incidence of egg contamination. Most freshly laid contaminated eggs contained fewer than 1 S . enteritidis cell/ml of egg yolk or albumen, and no sample contained more than 67 S. enteritidis cells/ml.