Recovery of salmonella serovar enteritidis from inoculated broiler hatching eggs using shell rinse and shell crush sampling methods

Authors: WEBB, MICHALEE - Claflin University; SPICKLER, JESSICA - University Of Georgia; Bourassa, Dianna; Cox Jr, Nelson; WILSON, JEANNA - University Of Georgia; Buhr, Richard - Jeff

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2014
Publication Date: 6/15/2014
Citation: Webb, M.L., Spickler, J.L., Bourassa, D.V., Cox Jr, N.A., Wilson, J.L., Buhr, R.J. 2014. Recovery of salmonella serovar enteritidis from inoculated broiler hatching eggs using shell rinse and shell crush sampling methods. Poultry Science. 93:(8)2117-2122.

Interpretive Summary: This study compared the recovery of Salmonella from hatching eggs using three sampling methods (eggshell rinsing, eggshell crush following a previous rinse, and eggshell crush without previous rinse). Eggshells were drop-inoculated with approximately 10, 100, or 1,000 cells/eggshell (relatively low levels) of Salmonella and allowed to dry at room temperature for 1 hour or 24 hours. The recovery of Salmonella 1 hour after inoculation for shell rinse sampled eggs was 16% positive at 10, 49% at 100, and 93% at 1,000 cells/eggshell challenge. For the shell crush with previous shell rinse sampled eggs recovery was 0% positive at 10, 3% at 100, and 17% at 1,000 cells/eggshell. The shell crush sampled eggs had recovery of 23% positive at 10, 69% at 100, and 96% at 1,000 cells/eggshell challenge. The recoveries of Salmonella 24 hour after inoculation were all significantly lower than at 1 hour. The shell rinse eggs were 3% positive at 10, 12% at 100, and 22% at 1,000 cells/eggshell challenge. Recovery for shell crush with previous shell rinse sampling was 2% positive at 10, 8% at 100, and 5% at 1,000 cells/eggshell challenge, and for the shell crush sampling recovery was 2% at 10, 32% at 100 and 42% at 1,000 cells/eggshell challenge. The significantly lower recovery from eggshells that were rinsed before sampling by eggshell crush indicates that sampling should occur prior to all sanitizing, rinsing, or washing of the eggs. Eggshell crush sampling was a more sensitive recovery by 10% than eggshell rinse at both 1 hour and 24 hours, but both methods were equally optimal when the inoculum was at 1,000 cells and samples collected after 1 hour. Waiting 24 hours after inoculation to sample significantly lowered the recovery for both the shell rinse and shell crush sampling methods by 40%. Future research should evaluate Salmonella recovery from eggshells for eggs sampled on the day of lay and compared to the recovery of those eggs held at room or the recommended refrigerated temperatures (45ºF for table eggs and 68ºF for hatching eggs) and sampled the following day.

Technical Abstract: This study compared the recovery of Salmonella from hatching eggs using three sampling methods (eggshell rinsing, eggshell crush following a previous rinse, and eggshell crush without previous rinse). Eggshells were drop-inoculated with approximately 10, 100, or 1,000 cfu/eggshell of S. Enteritidis and allowed to dry at room temperature for 1 h or 24 h. For the shell rinse groups, each inoculated egg was rinsed with buffered peptone water (BPW). 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 BPW. This same crush procedure was used for the shell crush without previous shell rinse eggs. The recovery of Salmonella 1 h after inoculation for shell rinse sampled eggs, 16% were positive at 10, 49% at 100, and 93% at 1,000 cfu/eggshell challenge. For the shell crush with previous shell rinse sampled eggs recovery was 0% positive at 10, 3% at 100, and 17% at 1,000 cfu/eggshell. For the shell crush sampled eggs had recovery of 23% positive at 10, 69% at 100, and 96% at 1,000 cfu/eggshell challenge. The recovery of Salmonella 24 h after inoculation for the shell rinse eggs was 3% positive at 10, 12% at 100, and 22% at 1,000 cfu/eggshell challenge, recovery for shell crush with previous shell rinse sampling was 2% positive at 10, 8% at 100, and 5% at 1,000 cfu/eggshell challenge, and for the shell crush sampling recovery was 2% at 10, 32% at 100 and 42% at 1,000 cfu/eggshell challenge. Eggshell crush was a more sensitive (~10 percentage points) sampling method than eggshell rinse at both 1 h and 24 h, but both methods were equally optimal when the inoculum was at 1,000 and samples 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 defeathered carcasses.