Pulse and continuous oral norfloxacin treatment of experimentally induced Escherichia coli infection in broiler chicks and turkey poults

Experimental colibacillosis was produced in 40 healthy, 7-day-old broiler chickens and turkeys by intratracheal injection of 1 x 10(8) CFU/chick and 1.23 x 10(9) CFU/poult bacteria of an O1:F11 strain of Escherichia coli, respectively. Two days before E. coli challenge all chicks were vaccinated with a live attenuated strain of infectious bronchitis virus (H-52). This model of infection--at least in chicken--proved to be useful for evaluating the efficacy of antimicrobial medication, by recording mortality, body weight gain, pathological alterations and frequency of reisolation of E. coli. Using this model, the efficacy of two different dosing methods of norfloxacin (continuous and pulse dosing) was evaluated. The once-per-day pulse dosing of norfloxacin administered via the drinking water at 15 mg/kg body weight proved to be more efficacious than the continuous dosing method of 100 mg/L for 5 days in chickens, while there were no convincing differences between the two treatment regimens in turkeys. The results confirmed earlier observations on the pharmacokinetic properties of norfloxacin in chicks and turkeys (Laczay et al., 1998).