Effect of Temperature on the Growth Response of Salmonella Enteritidis Inoculated onto the Vitelline Membranes of Fresh Eggs

Abstract

The growth response of Salmonella Enteritidis (SE) on the vitelline membrane in vitro was studied with the use of a special tube devised specifically for the inoculation of SE onto the vitelline membrane and for the sampling of the yolk near the inoculation site. This latter ability allowed the detection of the movement of SE into the yolk. The growth of SE on the membrane was compared with that of SE inoculated into yolk and albumen in vitro and in ovo in fresh in-shell eggs. The incubation time was 2 days, and the incubation temperatures were 4, 8, 15, 27, and 37°C. Comparison of the results obtained for in vitro growth showed that at 4, 8, and 15°C, SE behaved as if it were in the albumen, with its numbers decreasing over time. At 27 and 37°C, SE grew as if it were in yolk, with a maximum increase of 4.5 log CFU after 2 days at 37°C. In no experiments involving growth on the vitelline membrane did SE appear in the yolk. Comparisons between in vitro and in ovo growth responses of SE in yolk and albumen indicate that SE growth on the membrane parallels that in the in-shell egg.