MUTATION-RATE OF AVIAN INTESTINAL COLIFORM BACTERIA WHEN PRESSURED WITH FLUOROQUINOLONES

The purpose of this study was to determine the rate at which resistanc e developed in avian coliform bacteria when exposed to nalidixic acid, sarafloxacin, or enrofloxacin. In in vitro studies, the races of muta tion of avian isolates of Escherichia roll and Salmonella were determi ned following nalidixic add, sarafloxacin, or enrofloxacin pressure. T he rates of mutation were similar for nalidixic acid and sarafloxacin, whereas a lower rate of mutation was seen after enrofloxacin pressure . In in vivo studies, the quinolones were administered in the drinking water to broiler chickens at a concentration of 40 ppm for five conse cutive days. Samples of feces were inoculated onto appropriate media a nd the frequency of-resistance was determined. The frequency rates of resistance to nalidixic acid and sarafloxacin were similar. Enrofloxac in-medicated birds did not develop enrofloxacin-resistant coliform bac teria. The in vitro and in vivo data appear to correlate.