title: Prevalence and Quinolone Susceptibilities of Salmonella Isolated from the Feces of Preharvest Cattle Within Feedlots that Used a Fluoroquinolone to Treat Bovine Respiratory Disease.
abstract: Salmonella is an important foodborne pathogen and antimicrobial resistance can be a human health concern. The objectives of this cross-sectional study were to (1) determine the prevalence and quinolone susceptibility of Salmonella in feces of preharvest commercial feedlot cattle and (2) determine if the prevalence and susceptibility of Salmonella isolates were associated with previous fluoroquinolone use within pens. Five feedlots in western Kansas and Texas were selected based on their use of a commercially licensed fluoroquinolone for initial treatment of bovine respiratory disease (BRD). Twenty pen floor fecal samples were collected from each of 10 pens from each feedlot during early summer of 2012. Salmonella isolation was performed and microbroth dilution was used to determine susceptibility of isolates to nalidixic acid and ciprofloxacin. Prior antimicrobial treatment data were retrieved from feedlots' operational data. Generalized linear mixed models were used to assess associations between Salmonella prevalence and the number of fluoroquinolone treatments within pens while taking into consideration cattle demographic and management factors, as well as the hierarchical structure of the data. Overall, cumulative fecal prevalence of Salmonella was 38.0% (380/1000), but prevalence varied significantly (p < 0.01) among the five feedlots: 0.5% (1/200), 17.5% (35/200), 37.0% (74/200), 58.5% (117/200), and 76.5% (153/200). Salmonella serogroups included C1 (49.3%), E (36.4%), C2 (13.8%), and D (0.6%). There was no significant association (p = 0.52) between Salmonella prevalence and the frequency of fluoroquinolone treatments within a pen. All Salmonella isolates (n = 380) were susceptible to ciprofloxacin, while one isolate exceeded the human breakpoint (≥32 μg/mL) for nalidixic acid. In conclusion, Salmonella fecal prevalence in preharvest cattle was highly variable among feedlots. Nearly all Salmonella isolates were susceptible to quinolones, despite the fact that a fluoroquinolone was used as the primary therapeutic antimicrobial to treat BRD in these feedlot populations.
authors.affiliation: 1 Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas.|2 Bayer Healthcare , LLC, Animal Health Division, Shawnee Mission, Kansas.
authors.forename: Ashley B
authors.initials: AB
authors.lastname: Smith
authors.affiliation: 1 Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas.
authors.forename: David G
authors.initials: DG
authors.lastname: Renter
authors.affiliation: 1 Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas.
authors.forename: Natalia
authors.initials: N
authors.lastname: Cernicchiaro
authors.affiliation: 1 Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Shi
authors.affiliation: 1 Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University , Manhattan, Kansas.
authors.forename: Tiruvoor G
authors.initials: TG
authors.lastname: Nagaraja
mesh_terms: D000003:Abattoirs; D000822:Animal Husbandry; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial; D005243:Feces / Q000382:microbiology; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology* / Q000627:therapeutic use; D005516:Food Microbiology; D007615:Kansas / Q000453:epidemiology; D008297:Male; D008460:Meat; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D015995:Prevalence; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000662:veterinary*; D012475:Salmonella / Q000187:drug effects* / Q000302:isolation & purification; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D013781:Texas / Q000453:epidemiology
chemical_list: D024841:Fluoroquinolones