SUSCEPTIBILITY TO QUINOLONES OF SALMONELLA ISOLATED FROM MAN OR ANIMAL

Fluoroquinolones are efficacious antibiotics for the treatment of Salmonella 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 of Salmonella in animals, which may then contaminate humans. To evaluate current susceptibilities of Salmonella strains to quinolones, we collected 95 strains belonging to various serotypes in a district of intensive 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 (MICs) for the following antibiotics: nalidixic acid, norfloxacin, pefloxacin, ofloxacin, ciprofloxacin, levofloxacin and clinafloxacin. Our results 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 respectively 1 or 2 mg/l and 0.25 mg/l. For all the other human and animal strains 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 for clinafloxacin.