ARS | Publication request: Salmonella in lymph nodes of cattle presented for harvest

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2011
Publication Date: July 31, 2011
Citation: Gragg, S.E., Loneragan, G.H., Brichta-Harhay, D.M., Arthur, T.M., Bosilevac, J.M., Kalchayanand, N., Wang, R., Schmidt, J.W., Brooks, J.C., Shackelford, S.D., Wheeler, T.L., Brown, T.R., Brashears, M.M. 2011. Salmonella in lymph nodes of cattle presented for harvest [abstract]. International Association for Food Protection. p. 19. Abstract No. P1-62.

Technical Abstract: Introduction: Salmonella can invade and survive within host immune cells. Once internalized, these pathogens have the potential to disseminate throughout the lymphatic system and reside within lymph nodes. If so, because some lymph nodes are located within muscle and fat tissues, Salmonella-positive lymph nodes may potentially be incorporated into ground beef. Purpose: The purpose of this study was to determine the prevalence of Salmonella in subiliac lymph nodes obtained from cattle. Methods: Lymph nodes were collected from the carcasses of feedlot cattle and dairy cows in commercial packing plants prior to being trimmed to remove all fat and dipped in boiling water for three seconds before pulverization in a Whirl-pak bag and enrichment with 80 milliliters of tryptic soy broth. Enrichments were subjected to immunomagnetic separation (IMS), IMS beads were transferred to Rappaport-Vasiliadis Broth, incubated and these secondary enrichments were then streaked onto brilliant green sulfa agar and XLD agar. Presumptive Salmonella isolates were confirmed by invA PCR and serotyped. Results: Between September and November of 2010, the mean prevalence of Salmonella in cattle lymph nodes (n=1,039) was 8.7% (95% CI 0.93 – 16.6%). The majority of Salmonella were Montevideo and Anatum. Significance: Salmonella was readily recovered from subiliac lymph nodes and consequently, fat trim containing lymph nodes may be a point-source for Salmonella entry into ground beef products. The public health consequence of these findings should be further investigated and research is needed to better understand the routes of infection and opportunities to reduce the risk of Salmonella in lymph nodes of healthy cattle.