Recovery ofSalmonella serovar Enteritidis from inoculated broiler hatching eggs using shell rinse and shell crush sampling methods

Abstract

This study compared the recovery ofSalmonella from hatching eggs using 3 sampling methods (eggshell rinsing, eggshell crush following a previous rinse, and eggshell crush without previous rinse). Eggshells were drop-inoculated with approximately 101, 102, or 103 cfu/eggshell ofSalmonella Enteritidis and allowed to dry at room temperature for 1 or 24 h. For the shell rinse groups, each inoculated egg was rinsed with buffered peptone water. These rinsed eggs were used for the shell crush with previous rinse groups, and each egg was aseptically cracked, the contents discarded, and the eggshell and membranes crushed with buffered peptone water. This same crush procedure was used for the shell crush without previous shell rinse eggs. The recovery ofSalmonella 1 h after inoculation for shell rinse sampled eggs was 16% positive at 101, 49% at 102, and 93% at 103 cfu/eggshell challenge. For the shell crush with previous shell rinse, sampled egg recovery was 0% positive at 101, 3% at 102, and 17% at 103 cfu/eggshell. For the shell crush, sampled eggs had recovery of 23% positive at 101, 69% at 102, and 96% at 103 cfu/eggshell challenge. The recovery ofSalmonella 24 h after inoculation for the shell rinse eggs was 3% positive at 101, 12% at 102, and 22% at 103 cfu/eggshell challenge; recovery for shell crush with previous shell rinse sampling was 2% positive at 101, 8% at 102, and 5% at 103 cfu/eggshell challenge; and for the shell crush sampling recovery was 2% at 101, 32% at 102, and 42% at 103 cfu/eggshell challenge. Eggshell crush was a more sensitive (∼10 percentage points) sampling method than eggshell rinse at both 1 and 24 h, but both methods were equally optimal when the inoculum was at 103 and samples were collected after 1 h. Waiting 24 h after inoculation to sample significantly lowered the recovery for both the shell rinse and shell crush sampling methods by ∼40 percentage points.