Salmonella spp. in deep tissue lymph nodes of bovine origin: A systematic review and meta-analysis

Bovine deep tissue lymph nodes (DTLNs) are retained in bench trimmings during carcass fabrication and enter the ground beef supply, making Salmonella contamination in DTLNs a recognized food safety concern. To characterize this contamination and provide quantitative inputs for microbial risk assessment, this study applied systematic review and meta-analysis to synthesize evidence on Salmonella prevalence and concentration in bovine DTLNs. Of 490 records initially retrieved from two bibliographic databases and grey literature, 33 were identified as relevant and included in meta-analyses. The pooled Salmonella prevalence in DTLNs was 10.8% (95% CI [7.5, 14.5]), with significant heterogeneity between studies. Subgroup analyses revealed higher prevalence during the warm season compared to the cool season (10.7% vs. 3.8%), in feedlot cattle compared to cull cattle (13.5% vs. 3.4%), and in subiliac lymph nodes (18%). The most prevalent serotypes were Anatum, Reading, Montevideo, Dublin, Typhimurium, Cerro, and Kentucky. Antimicrobial resistance (AMR) data was sparse and methodologically inconsistent. Among the two largest studies, most isolates were pan-susceptible (80.6-86%), with multidrug resistance in a minority (8.3-10.7%); resistance to tetracycline, streptomycin, and chloramphenicol was most common, while resistance to antibiotics used for treating human salmonellosis was lower but present. Concentration data were substantially underreported, with only two studies providing sufficient data for a preliminary quantitative synthesis. Overall, dominant serotypes, seasonal patterns, and major AMR profiles in DTLNs were consistent with those reported in beef products. These findings provide a quantitative foundation for risk assessment and evaluation of DTLN-targeted interventions to mitigate salmonellosis risks associated with ground beef consumption.