title: Antimicrobial resistance in Campylobacter coli selected by tylosin treatment at a pig farm.
abstract: Limited knowledge is available regarding the dynamics of macrolide resistance under farm conditions with natural Campylobacter populations. We examined the dynamics of antimicrobial resistance in Campylobacter coli at a large pig farm. Faeces were sampled from untreated sows and piglets (n=57), weaned pigs treated with tylosin (n=68) and pigs of the same group 3-5 weeks after withdrawal of tylosin (n=15). Additionally, 48 weaned pigs were sampled after tylosin had not been administered for 7 months at the farm. MICs for seven antimicrobials were determined, isolates were genotyped by PFGE and mutations conferring macrolide resistance were identified. Resistance to at least one antimicrobial agent was higher (P<0.001) in the isolates from the treated pigs (30 of 56) than in those from the untreated animals (2 of 40). Resistance to ciprofloxacin, erythromycin, nalidixic acid and streptomycin was higher (P<0.05) in the isolates from the treated pigs than in those from the untreated animals. All 14 erythromycin-resistant isolates studied (MIC ≥ 512 μg/ml) contained mutation A2075G in 23S rRNA. Resistance against at least one antimicrobial was significantly lower (P<0.05) when tylosin had not been administered for 7 months. Resistance to erythromycin and streptomycin also decreased (P<0.05). PFGE analysis revealed a change of genotypes induced by tylosin treatment. In conclusion, tylosin treatment of pigs selected for a high-level of resistance to erythromycin and resistance to ciprofloxacin, nalidixic acid and streptomycin also increased in C. coli isolates within a few days.
authors.affiliation: Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, P.O. Box 66, FI-00014 University of Helsinki, Finland. joan.smyth@uconn.edu
authors.forename: P
authors.initials: P
authors.lastname: Juntunen
authors.forename: H
authors.initials: H
authors.lastname: Heiska
authors.forename: S
authors.initials: S
authors.lastname: Olkkola
authors.forename: A-L
authors.initials: AL
authors.lastname: Myllyniemi
authors.forename: M-L
authors.initials: ML
authors.lastname: Hänninen
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002169:Campylobacter Infections / Q000188:drug therapy / Q000662:veterinary*; D017000:Campylobacter coli / Q000187:drug effects* / Q000235:genetics; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D005260:Female; D005838:Genotype; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D013552:Swine / Q000382:microbiology; D013553:Swine Diseases / Q000188:drug therapy* / Q000382:microbiology; D015645:Tylosin / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D012338:RNA, Ribosomal, 23S; D015645:Tylosin