title: Animal and farm influences on the dynamics of antibiotic resistance in faecal Escherichia coli in young dairy calves.
abstract: It is believed that the intensive use of antibiotics in the management of disease in pre-weaned calves contributes to high levels of antibiotic resistance in commensal and pathogenic bacteria. We described the temporal dynamics of antibiotic-susceptibility patterns seen in bovine enteric Escherichia coli in pre-weaned calves on dairy farms and dedicated calf-rearing facilities. Cohorts of 30 calves at each of six farms were sampled at 2-week intervals during the pre-weaning period. Faecal E. coli isolates were analyzed for antibiotic susceptibility to 12 antibiotics with the disk-diffusion method and grouped using cluster analysis of inhibition-zone patterns. The influences of calf age, farm-type, and individual-calf antibiotic therapy on the clusterings were assessed using stratified analyses and cumulative multinomial logistic regression using generalized estimating equation with antibiotic-resistance cluster as an ordinal-dependent variable. The model controlled for farm and cohort by a nested design and included a repeated measure on calf at each sampling occasion. E. coli from calves 2 weeks of age were more likely to be increasingly multiply resistant than E. coli from day-old calves (OR = 53.6), as were 4- and 6-week-old calves (OR = 29.8 and 16.4, respectively). E. coli from calves on dedicated calf-rearing facilities were more likely to be increasingly multiply resistant than E. coli from dairy-reared calves (OR = 2.4). E. coli from calves treated with antibiotics within 5 days prior to sampling were also more likely to be increasingly multiply resistant than E. coli from calves not exposed to individual antibiotic therapy (OR = 2.0).
authors.affiliation: Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, 18830 Road 112, Tulare, 93274 CA, USA. caberge@ucdavis.edu
authors.forename: A C B
authors.initials: AC
authors.lastname: Berge
authors.forename: E R
authors.initials: ER
authors.lastname: Atwill
authors.forename: W M
authors.initials: WM
authors.lastname: Sischo
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002140:California / Q000453:epidemiology; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D015331:Cohort Studies; D003612:Dairying; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D005260:Female; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D011446:Prospective Studies
chemical_list: D000900:Anti-Bacterial Agents