Association of antimicrobial resistance in Campylobacter isolated from food-producing animals with antimicrobial use on farms.

On 1,374 food-producing animal farms in 2001-2004, we investigated the influence of antimicrobial usage within 6 months before a survey conducted on antimicrobial resistance in Campylobacter. Tetracyclines and fluoroquinolones were used for therapeutic purposes on 107 and 21 farms, respectively. Oxytetracycline-resistant C. jejuni and C. coli were found in 57.1% (8/14) and 92.5% (37/40) of the farms, respectively, when the animals were treated with tetracyclines. However, they were found in 43.2% (112/259) and 74.3% (122/164) of the farms, respectively, when the animals were not treated with tetracyclines. Enrofloxacin-resistant C. jejuni and C. coli were found in 66.7% (2/3) and 16.7% (1/6) of the farms, respectively, when the animals were treated with fluoroquinolones. However, they were found in 15.5% (42/270) and 28.8% (57/198) of the farms, respectively, when the animals were not treated with fluoroquinolones. The percentage of oxytetracycline resistance in C. coli was significantly elevated when the animals were treated with tetracyclines (P < 0.05). The farms on which antimicrobials included by their resistance pattern were used accounted for 9.1% (4/44) and 24.1% (14/58) of the farms where enrofloxacin-resistant C. jejuni and C. coli were isolated, respectively. It is likely that several factors account for the presence of fluoroquinolone-resistant Campylobacter.