|Cox, Nelson - Nac|
|MEDINA, DAVID - Gettysburg College|
|Cook, Kimberly - Kim|
|SHARIAT, NIKKI - University Of Georgia|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2019
Publication Date: 9/19/2019
Citation: Cox Jr, N.A., Berrang, M.E., House, S.L., Medina, D., Cook, K.L., Shariat, N.W. 2019. Population analyses reveal preenrichment method and selective enrichment media affect Salmonella serovars detected on broiler carcasses. Journal of Food Protection. 82(10):1688-1696. https://doi.org/10.4315/0362-028X.JFP-19-166.
Interpretive Summary: The inability to assess diversity on a sample of a broiler carcass rinse with presently used laboratory methods means that perhaps serovars most often associated with human illness may be masked by more abundant Salmonella. By comparing an amplicon-based next generation sequencing tool (CRISPR-SeroSeq) to standard laboratory methods, many more naturally occurring serovars were detected on broiler carcasses with the new technology. This will assist in trace backs and also a more accurate understanding of ecology of Salmonella in poultry.
Technical Abstract: Poultry is a major Salmonella reservoir, but conventional culture-based methods typically identify the most abundant serovars while those less abundant remain undetected. Choice of enrichment procedure also introduces bias and, for broiler carcasses, a one-minute rinse prior to pre-enrichment is insufficient to release all Salmonella present. The inability to assess serovar diversity means that serovars more often associated with human illness may be masked by more abundant Salmonella. CRISPR-SeroSeq, an amplicon-based next-generation sequencing tool, allows detection of multiple serovars and maps the relative serovar frequencies in a sample. To address the limitations above, CRISPR-SeroSeq was used on broiler carcasses collected pre-chill at a commercial plant. Standard carcass rinse aliquot pre-enrichments and whole carcass pre-enrichments that were both enriched in Rappaport Vassiliadis (RV) and tetrathionate (TT) broths were compared. On average, five serovars were observed per carcass, including nine on one carcass. CRISPR-SeroSeq detected serovars comprising as low as 0.005% of the population. CRISPR SeroSeq data matched (28/32) with standard culture analysis for abundant serovars. Serovars Kentucky, Typhimurium, and Schwarzengrund were found on each carcass. Overall serovar diversity was higher in whole carcass pre-enrichments that were enriched in RV (p<0.05). Serovar Schwarzengrund was present at higher frequencies in whole carcass pre-enrichments compared to rinse aliquot pre-enrichments (t-test, p<0.05), suggesting it adheres more strongly to the carcass. Serovar Enteritidis, was enriched 8-fold more in TT than RV, and serovars Schwarzengrund and Reading were preferentially enriched in RV. Comparison of pre-enriched and enriched samples suggest that selective enrichment in RV or TT was inhibitory to some serovars. This study addresses limitations to current Salmonella surveillance protocols and provides valuable information relating to Salmonella population dynamics.