Antibiotic susceptibility was determined by disc diffusion on
Mueller–Hinton agar, in accordance with the guidelines of the Antibiogram
Committee of the French Society for Microbiology [22 ]. The following antimicrobial drugs (Bio-Rad, Marnes-la-Coquette,
France) were tested: ampicillin, cefalotin, cefotaxime, streptomycin,
chloramphenicol, erythromycin, azithromycin, sulfonamides,
trimethoprim-sulfamethoxazole, vibriostatic agent O/129, tetracycline,
doxycycline, minocycline, nalidixic acid, norfloxacin, ofloxacin, pefloxacin,
ciprofloxacin, nitrofurantoin, polymyxin B and colistin (polymyxin E).
Escherichia coli CIP 76.24 (ATCC 25922) was used as a
control. The minimum inhibitory concentrations (MICs) of nalidixic acid and
ciprofloxacin were determined by Etests (bioMérieux, Marcy
L'Etoile, France). The MICs of colistin and polymyxin B were determined
with custom-produced Sensititre microtitre plates (Thermo Fisher Scientific,
East Grinstead, UK) and MIC test strips (Liofilchem, Roseto degli Abruzzi,
Italy), respectively, on 34 isolates chosen on the basis of resistance
phenotype, year and country of isolation.
Mueller–Hinton agar, in accordance with the guidelines of the Antibiogram
Committee of the French Society for Microbiology [22 ]. The following antimicrobial drugs (Bio-Rad, Marnes-la-Coquette,
France) were tested: ampicillin, cefalotin, cefotaxime, streptomycin,
chloramphenicol, erythromycin, azithromycin, sulfonamides,
trimethoprim-sulfamethoxazole, vibriostatic agent O/129, tetracycline,
doxycycline, minocycline, nalidixic acid, norfloxacin, ofloxacin, pefloxacin,
ciprofloxacin, nitrofurantoin, polymyxin B and colistin (polymyxin E).
Escherichia coli CIP 76.24 (ATCC 25922) was used as a
control. The minimum inhibitory concentrations (MICs) of nalidixic acid and
ciprofloxacin were determined by Etests (bioMérieux, Marcy
L'Etoile, France). The MICs of colistin and polymyxin B were determined
with custom-produced Sensititre microtitre plates (Thermo Fisher Scientific,
East Grinstead, UK) and MIC test strips (Liofilchem, Roseto degli Abruzzi,
Italy), respectively, on 34 isolates chosen on the basis of resistance
phenotype, year and country of isolation.