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United States Department of Agriculture

Agricultural Research Service

Research Project: EXPLORING GENOMIC DIFFERENCES AND ECOLOGICAL RESERVOIRS TO CONTROL FOODBORNE PATHOGENS

Location: Meat Safety & Quality Research

Title: Salmonella in lymph nodes of cull and fed cattle at harvest

Authors
item Webb, H -
item Harhay, Dayna
item Gragg, S -
item Brashears, M -
item Nightingale, K -
item Arthur, Terrance
item Bosilevac, Joseph
item Kalchayanand, Norasak
item Schmidt, John
item Wang, Rong
item Lonergan, G -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 2013
Publication Date: March 10, 2013
Citation: Webb, H.E., Harhay, D.M., Gragg, S.E., Brashears, M.M., Nightingale, K.K., Arthur, T.M., Bosilevac, J.M., Kalchayanand, N., Schmidt, J.W., Wang, R., Lonergan, G.H. 2013. Salmonella in lymph nodes of cull and fed cattle at harvest. IN: Proceedings of The Beef Industry Summit 2013, March 13-15, 2013, Dallas Texas, 2013 FLASHDRIVE.

Technical Abstract: Category: Pre-harvest pathogen reduction Objective: To evaluate the potential association between Salmonella enterica burden within bovine subiliac lymph nodes (LNs), animal type, season, and region of harvest. Methods: Bovine LNs (n = 4,764) were collected from 12 abattoirs, 8 that primarily harvest fed cattle, 2 that primarily harvest cull or dairy cattle and 2 both harvest fed and cull. Plants were located in BIFSCo regions 2, 3, 4, 5, and 8 (n= 3, 5, 2, 1, 1, respectively). Subiliac LNs were collected during the months of February through November. LNs were trimmed of surrounding fat, surface sterilized by submersion in boiling water for 3 seconds, pulverized in individual bags with a rubber mallet, and homogenized for 2 minutes at 230 revolutions per minute. Samples were then enriched in tryptic soy broth for 12h at 42'C and immunomagnetic separation was performed on the enrichments using paramagnetic beads. Beads were transferred to Rappaport-Vasiliadis broth for secondary enrichment at 42'C for 18-20h, and then plated onto xylose lysine desoxycholate and brilliant green sulfa agars and incubated for 18-20hrs at 37'C. Morphologically characteristic isolates were serotyped and their susceptibility to a panel of 15 antimicrobials determined. Key Results: Observed median percent prevalence estimates were 1.3, 2.0, 0.0, 0.0 and 0.0, for regions 2, 3, 4, 5, and 8, respectively. Overall, mean prevalence in feedlot cattle was 7.9% while that for cull cattle was 1.9%. Salmonella was detected in 274 (5.8%) LNs and 155 had quantifiable levels of Salmonella that varied from <1.6 to 4.6 log10 cfu/LN. Preliminary serotyping data (n = 134 isolates) indicate the most common serotypes recovered were Montevideo (33.6%) and Anatum (16.4%). To date, antimicrobial susceptibility testing has been performed on 232 isolates. The majority, (84.9%) of the isolates were pansusceptible; however, the ACSSuT resistance phenotype was observed in 8.1% of the isolates. Application to the Industry: Our preliminary data confirms the relatively rare occurrence of Salmonella in LNs of cattle during the winter and spring period. We did, however, observe an increase in prevalence during the summer and fall period, particularly in BIFSCo Region 3. Salmonella harbored in the LNs is protected from typical in-plant antimicrobial interventions applied to the surface of animals and their carcasses. As lymph nodes are commonly incorporated into ground beef at usual proportions, Salmonella harborage in the lymph nodes may be an important food safety concern. Our preliminary data help characterize the region, season, and animal type for which additional control of Salmonella may be warranted. Funding: This project was funded by The Beef Checkoff and USDA/NIFA/NIFSI Contract # 2011-51110-31081

Last Modified: 11/22/2014
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