SUSCEPTIBILITY TO QUINOLONES OF SALMONELL A ISOLATED FROM MAN OR ANIMAL

Fluoroquinolones are efficacious antibiotics for the treatment of Salm onella infections in humans. One of these quinolones, enrofloxacin, a precursor of ciprofloxacin, is used to treat respiratory infections in calves and poultry. There is a risk of developing resistant strains o f Salmonella in animals, which may then contaminate humans. To evaluat e current susceptibilities of Salmonella strains to quinolones, we col lected 95 strains belonging to various serotypes in a district of inte nsive breeding (the Ille-et-Vilaine Department): 54 human strains, 24 bovine strains, and 17 poultry strains. The technique of dilutions in agar medium was used to determine Minimal Inhibitory Concentrations (M ICs) for the following antibiotics: nalidixic acid, norfloxacin, peflo xacin, ofloxacin, ciprofloxacin, levofloxacin and clinafloxacin. Our r esults showed that human Salmonella strains remained very susceptible to quinolones. Only 3 animal strains had nalidixic-acid MICs > 128 mg/ l. For these 3 strains, pefloxacin and ciprofloxacin MICs were respect ively 1 or 2 mg/l and 0.25 mg/l. For all the other human and animal st rains the nalidixic-acid MICs were < 4 mg/l, and their MICs 90 were: 0 .12mg/l for ofloxacin and norfloxacin, 0.06 mg/l for pefloxacin, 0.03 mg/l for ciprofloxacin, 0.016 mg/l for levofloxacin, and 0.004 mg/l fo r clinafloxacin.