Pooling of laying hen housing system environmental swabs and efficacy of Salmonella spp. detection

Authors: Jones, Deana; Gast, Richard; REGMI, PRAFULLA - Purdue University; Ward, Garrett; ANDERSON, KENNETH - North Carolina State University; KARCHER, DARRIN - Purdue University

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2019
Publication Date: 6/15/2019
Citation: Jones, D.R., Gast, R.K., Regmi, P., Ward, G.E., Anderson, K.E., Karcher, D.M. 2019. Pooling of laying hen housing system environmental swabs and efficacy of Salmonella spp. detection. Poultry Science. 98(1):205.

Interpretive Summary: Under the FDA Egg Rule in the US, egg producers are required to conduct mandatory environmental sampling for the detection of Salmonella Enteritidis (SE) at set time frames corresponding to pullet, post-peak, and post-molt production phases. The egg producer assumes the costs for the mandatory testing. Since outcomes are based on the overall presence of SE, pooling of swabs has been discussed to reduce the fiscal burden. The current study was conducted to determine the efficacy of detecting Salmonella Enteritidis, Heidelberg (SH), and Typhimurium (ST) in single and pooled swabs. Laying hen flocks housed in conventional cage (scraper blade swabs) and cage-free slat floor (drag swabs) were monitored for all mandatory environmental phases. Each of the isolates utilized were 200 ppm nalidixic acid-resistant. A high (100 cfu) or low (10 cfu) dose of inoculum was introduced on a sample swab. Additional non-inoculated swabs were added to the bag resulting in pools of 1, 2, or 4 swabs. After non-selective pre-enrichment, aliquots were introduced into both tetrathionate (TT) and Rappaport-Vassiliadis (RV) selective enrichment. Data was sorted for isolate and swab type and Chi square analysis to determine difference in prevalence for the number of swabs in a pool within a selective enrichment method. The greatest recovery, regardless of number of swabs, occurred in the 100 cfu inoculum concentration. Single swabs always had the highest rate of detection. SH had the lowest level of detection in scraper blade swabs (58 – 8 %) compared to ST with the greatest (84 – 32 %). The greatest detection in the 10 cfu dose occurred in single drag swabs (90 – 58 %) compared to scraper blade swabs (58 – 25 %). SE (P < 0.05) and ST (P < 0.05) recovery was negatively impacted by increasing swabs in the sample. The addition of swabs to sample pools reduced the rate of recovery due to the increased flora competing in enrichment procedures.

Technical Abstract: Under the FDA Egg Rule in the US, egg producers are required to conduct mandatory environmental sampling for the detection of Salmonella Enteritidis (SE) at set time frames corresponding to pullet, post-peak, and post-molt production phases. The egg producer assumes the costs for the mandatory testing. Since outcomes are based on the overall presence of SE, pooling of swabs has been discussed to reduce the fiscal burden. The current study was conducted to determine the efficacy of detecting Salmonella Enteritidis, Heidelberg (SH), and Typhimurium (ST) in single and pooled swabs. Laying hen flocks housed in conventional cage (scraper blade swabs) and cage-free slat floor (drag swabs) were monitored for all mandatory environmental phases. Each of the isolates utilized were 200 ppm nalidixic acid-resistant. A high (100 cfu) or low (10 cfu) dose of inoculum was introduced on a sample swab. Additional non-inoculated swabs were added to the bag resulting in pools of 1, 2, or 4 swabs. After non-selective pre-enrichment, aliquots were introduced into both tetrathionate (TT) and Rappaport-Vassiliadis (RV) selective enrichment. Data was sorted for isolate and swab type and Chi square analysis to determine difference in prevalence for the number of swabs in a pool within a selective enrichment method. The greatest recovery, regardless of number of swabs, occurred in the 100 cfu inoculum concentration. Single swabs always had the highest rate of detection. SH had the lowest level of detection in scraper blade swabs (58 – 8 %) compared to ST with the greatest (84 – 32 %). The greatest detection in the 10 cfu dose occurred in single drag swabs (90 – 58 %) compared to scraper blade swabs (58 – 25 %). SE (P < 0.05) and ST (P < 0.05) recovery was negatively impacted by increasing swabs in the sample. The addition of swabs to sample pools reduced the rate of recovery due to the increased flora competing in enrichment procedures.