title: Microbiological analysis of bovine lymph nodes for the detection of Salmonella enterica.
abstract: Bovine peripheral lymph nodes (LNs) have been identified as a potential source of Salmonella when trim containing these nodes is incorporated into ground beef. Studies examining the prevalence of Salmonella in peripheral LNs of cattle are few in number, and the microbiological  methods used for these analyses have not been validated. Given that Salmonella contamination may be found on postintervention carcasses, it is important to understand the extent to which Salmonella contamination from surrounding adipose tissue is transferred to LN samples during  sample preparation. To better understand the potential for crosscontamination, 906 LN samples were collected from postintervention carcasses and these, along with the corresponding adipose trim (AT), were analyzed for the presence of Salmonella. The results showed that the Salmonella  prevalence in LNs and on AT was 0.8 and 5 % , respectively, but that it was possible to find AT positive for Salmonella contamination while the corresponding LNs were negative and vice versa. In order to examine the dynamics of cross-contamination between surface adipose tissue and  LNs in the trimming process, inoculation studies were performed. The efficacy of LN submersion in boiling water as a means of surface sterilization and the effect of boiling on the viability of Salmonella contained within LN samples were also examined. The results showed that, on average,  23 to 43 % of the inoculated LN samples in this study were cross-contaminated by Salmonella on surrounding adipose tissue when present in the range of 10(1) to 10(2) CFU per sample; however, surface decontamination methods were very effective at removing Salmonella  cross-contaminants in this range.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, Clay Center, NE 68933-0166, USA. dayna.harhay@ars.usda.gov
authors.forename: Dayna M
authors.initials: DM
authors.lastname: Brichta-Harhay
authors.forename: Terrance M
authors.initials: TM
authors.lastname: Arthur
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Bosilevac
authors.forename: Norasak
authors.initials: N
authors.lastname: Kalchayanand
authors.forename: John W
authors.initials: JW
authors.lastname: Schmidt
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Steven D
authors.initials: SD
authors.lastname: Shackelford
authors.forename: Guy H
authors.initials: GH
authors.lastname: Loneragan
authors.forename: Tommy L
authors.initials: TL
authors.lastname: Wheeler
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000635:transmission; D015169:Colony Count, Microbial; D005506:Food Contamination / Q000032:analysis* / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005525:Food-Processing Industry / Q000592:standards; D006801:Humans; D008198:Lymph Nodes / Q000382:microbiology*; D008461:Meat Products / Q000382:microbiology*; D015995:Prevalence; D012481:Salmonella Infections, Animal / Q000382:microbiology / Q000635:transmission; D019779:Salmonella enterica / Q000302:isolation & purification*