Diversity of Multidrug-Resistant Salmonella enterica Strains Associated with Cattle at Harvest in the United States

Abstract

The prevalence and diversity of multidrug-resistant (MDR) Salmonella enterica strains associated with cattle at harvest in the United States were examined. Hides and carcasses of cattle were sampled at processing plants (n ‫؍‬ 6) located in four geographically distant regions from July 2005 to April 2006. The mean prevalences of Salmonella on hides, preevisceration carcasses (immediately after hide removal), and postintervention carcasses (in the chiller and after the full complement of interventions) were 89.6%, 50.2%, and 0.8%, respectively. The values for MDR Salmonella enterica strains (defined as those resistant to two or more antimicrobials) as percentages of Salmonella prevalence were 16.7% (95% confidence interval [CI], 8.3 to 25.1%; median percent prevalence, 6.9%), 11.7% (95% CI, 4.4 to 19.0%; median, 4.8%), and 0.33% (95% CI, ؊0.3 to 0.70%; median, 0%), respectively. In this study, 16,218 Salmonella hide and carcass isolates were screened for antimicrobial resistance. Of these, 978 (6.0%) unique MDR S. enterica isolates were identified and serotyped and their XbaI pulsed-field gel electrophoresis (PFGE) profiles determined. The predominant MDR S. enterica serotypes observed were Newport (53.1%), Typhimurium (16.6%), and Uganda (10.9%). Differences in MDR S. enterica prevalence were detected, and PFGE analysis revealed both epidemic clusters (profiles found in plants in multiple regions/seasons) and endemic clusters (profiles observed in plants in limited regions/seasons) within several of the MDR serotypes examined. Despite these differences, multiple-hurdle processing interventions employed at all plants were found to be quite effective and decreased Salmonella carcass contamination by 98.4% (95% CI, 97.6 to 99.7%).

Prevalence and characterisation of Salmonella in slaughtered cattle and beef in Poland

“…Similar study in Venezuela revealed that 36.3% of bovine hides and 7.2% of the corresponding carcasses after evisceration were positive for this pathogen (16). In the USA, Salmonella-positive samples were identified, depending on the season, on 86.1% -93.8% hides (spring and summer) and on 44.2% -55.3% carcasses (spring and winter), respectively (6). In Europe, the percentage of contaminated bovine hides varied depending on the author, place of sampling, and season of the year.…”

“…To assess the routes of transmission and molecular relatedness of Salmonella isolates along the food chain, usually the pulsed field gel electrophoresis (PFGE) method is applied due to its discriminatory power and reproducibility (6,21). This approach allows establishing routes and sources of carcass contamination with these pathogenic bacteria at abattoirs and at the meat level.…”

Occurrence of Antimicrobial-Resistant Escherichia coli and Salmonella enterica in the Beef Cattle Production and Processing Continuum

“…Brichta-Harhay et al (58) demonstrated that 3GC r Salmonella spp. were a subpopulation of generic Salmonella in beef processing environments using extensive antimicrobial susceptibility analysis of generic Salmonella isolates (i.e., isolates of colonies grown on media permissive for Salmonella regardless of antimicrobial susceptibility), but the concentrations of 3GC…”

Substantial within-Animal Diversity of Salmonella Isolates from Lymph Nodes, Feces, and Hides of Cattle at Slaughter

“…Arthur and colleagues (20) isolated Salmonella (n ϭ 18) from subiliac and superficial cervical lymph nodes and reported resistance among 22.2% (n ϭ 4) of isolates, with 16.7% (n ϭ 3) demonstrating MDR phenotypes. Salmonella antimicrobial resistance poses a challenge to human medicine, as ceftriaxone, an extended-spectrum cephalosporin, is a common choice for treating salmonellosis in children (38). Adult salmonellosis is often treated with nalidixic acid and ciprofloxacin, a quinolone and fluoroquinolone, respectively (38).…”