Effects of fluoroquinolone treatment and group housing of pigs on the selection and spread of fluoroquinolone-resistant Campylobacter

There are concerns that the use of fluoroquinolones (FQs) and group housing of food animals may contribute to the development of bacterial FQ resistance. Here, we studied the effects of administering FQ to pigs on the selection of FQ-resistant Campylobacter. Fifteen pigs were randomly allocated to either a group treated with FQs (enrofloxacin or norfloxacin), or an untreated control group. The number of FQ-resistant Campylobacter in feces was determined using appropriate selective agar containing enrofloxacin. FQ-resistant Campylobacter from samples of both groups were observed on days 3 and 4. These bacteria persisted for up to 21 days after treatment was discontinued. To evaluate the effect of group housing on the transmission of FQ-resistant Campylobacter, five pigs infected with FQ-sensitive Campylobacter pigs and one pig infected with FQ-resistant Campylobacter were housed together. On day 3, FQ-resistant Campylobacter were isolated from all six pigs. Moreover, FQ-resistant Campylobacter were isolated from environmental samples from the pen. These results indicate that the treatment of pigs with FQs selects for and spreads FQ-resistant Campylobacter among the pen. Therefore, responsible and prudent use of FQs at pig farms is required to prevent the emergence and transmission of FQ-resistant Campylobacter.