Prevalence and antimicrobial resistance among Campylobacter spp. in Louisiana retail chickens after the enrofloxacin ban.

Effective in September 2005, enrofloxacin, a fluoroquinolone group antimicrobial, was withdrawn from use in the U.S. poultry farms. In this 1-year study initiated in October 2006, we isolated and characterized Campylobacter spp. from Louisiana retail conventionally raised (n = 141) and organic (n = 53) chickens as a comparison to evaluate the postban bacterial resistance to antimicrobials. Campylobacter was present in 43.3% of the chickens; similar rates were observed among conventional and organic chickens. A total of 165 Campylobacter isolates were recovered, with Campylobacter jejuni being the predominant species (66.7%). No apparent seasonal trend was deduced from the prevalence data. Further, the two main conventional and one organic chicken brands did not carry significantly different rates of Campylobacter (p > 0.05). The most common resistance observed was to tetracycline (31.5%), followed by erythromycin (20%) and ciprofloxacin (6.1%). No resistance to gentamicin was identified. All Campylobacter isolates recovered from organic chickens (n = 48) were susceptible to ciprofloxacin, compared to 8.5% resistance rate for those from conventional chickens (n = 117). Additionally, the resistance rate to erythromycin was significantly higher in Campylobacter isolates from conventional chickens (23.9%) than those from organic chickens (10.4%; p < 0.05). Our results demonstrated a low prevalence and low ciprofloxacin resistance rate of Campylobacter in Louisiana retail chickens after the enrofloxacin ban. Further studies involving a larger sample size over time are warranted to better assess the effects of banning enrofloxacin use in poultry and the levels of fluoroquinolone-resistant Campylobacter.