SALMONELLA PENETRATION THROUGH EGGSHELL ASSOCIATED WITH FRESHNESS OF LAID EGGS AND REFRIGERATION

Effects of egg age after laying and refrigeration on penetration of th e eggshell by Salmonella enteritidis (SE) and Salmonella typhimurium ( ST) were examined. Eggs 0.25 to 3 h, 3.25 to 6 h, 1 day, and 7 days ol d held at two temperatures were immersed in SE or ST suspensions conta ining 10(3) or 10(6) CFU/ml at 25 degrees C for 10 min. After holding at 25 degrees C for 2 h, the inner eggshell and egg contents were exam ined for Salmonella cells. The recovery rates of Salmonella cells from both the inner eggshell and egg contents of the 0.25- to 3-h-old eggs were significantly higher than those of other groups, especially at t he high-exposure dose. There was no significant difference noted betwe en SE and ST in ability to penetrate through eggshell. Salmonella pene tration was significantly decreased by cooling the eggs at 4 degrees C for 15 min prior to immersing them in SE or ST suspension. The data s uggested that Salmonella cells readily penetrated through the shell of freshly laid eggs, but that this penetration was suppressed by coolin g the eggs before they were exposed to Salmonella suspensions.