title: Identification of Escherichia coli and Salmonella enterica organisms with reduced susceptibility to ceftriaxone from fecal samples of cows in dairy herds.
abstract: OBJECTIVE
  To estimate the relationship between therapeutic use of ceftiofur and recovery of Escherichia coli and Salmonella spp with reduced susceptibility to ceftriaxone from feces of dairy cattle.
  
  
  METHODS
  3,840 mature dairy cows on 50 dairy herds in Ohio. Procedures-Fecal samples were obtained from up to 100 mature dairy cows on each farm. Samples were screened for E coli and Salmonella spp with reduced susceptibility to ceftriaxone by use of selective media.
  
  
  RESULTS
  E coli with reduced susceptibility to ceftriaxone was recovered from 92% (46/50) of the herds and 60.9% (2,338/3,840) of cows. Salmonella spp were recovered from 44% (22/50) of the herds and 9.9% (382/3,840) of cows. No association was found between ceftiofur use and recovery of E coli with reduced susceptibility to ceftriaxone at the herd level. However, recovery of E coli with reduced susceptibility to ceftriaxone was more likely from cows in herds in which Salmonella spp were also recovered on the day of collection (odds ratio, 24.96; 95% confidence interval, 3.17 to 196.68) than from herds in which Salmonella spp were not recovered. Odds of recovery of E coli with reduced susceptibility to ceftriaxone from an individual cow increased 62% (odds ratio, 1.62; 95% confidence interval, 1.16 to 2.25) for every 454-kg increase in herd milk production.
  
  
  CONCLUSIONS
  No evidence was found that the use of ceftiofur on dairy farms increases the prevalence or dissemination of Salmonella spp or E coli with reduced susceptibility to ceftriaxone.
authors.affiliation: Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Luke C
authors.initials: LC
authors.lastname: Heider
authors.forename: Julie A
authors.initials: JA
authors.lastname: Funk
authors.forename: Armando E
authors.initials: AE
authors.lastname: Hoet
authors.forename: Richard W
authors.initials: RW
authors.lastname: Meiring
authors.forename: Wondwossen A
authors.initials: WA
authors.lastname: Gebreyes
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wittum
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002443:Ceftriaxone / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D005260:Female; D019779:Salmonella enterica / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D002443:Ceftriaxone; C053503:ceftiofur