Combined in vitro effects of orbifloxacin and fosfomycin on S. Dublin and S. Typhimurium isolated from calves
2000
Matsumoto, S. (Dainippon Pharmaceutical Co. Ltd., Suita, Osaka (Japan)) | Kitadai, N. | Nakata, K. | Katae, H.
This study determined minimal inhibitory concentrations (MIC) of orbifloxacin (OBFX), fosfomycin (FOM), and several antibacterial agents against Salmonella Dublin and Salmonella Typhimurium isolated from calves. For 90% of the isolates tested, MICs of OBFX were 1.56 mu-g/ml against S. Dublin and 0.2 mu-g/ml against S. Typhimurium. Antibacterial potencies of OBFX against tested organisms were higher than those of oxolinic acid (OA), kanamycin (KM), gentamicin (GM), oxytetracycline (OTC), ampicillin (ABPC), sulfamethoxazole (SMX), trimethoprim (TMP), fosfomycin (FOM), and bicozamycin (BCM). All isolates were considered susceptible to OBFX, FOM, GM, TMP, and BCM. After establishing these properties, we assessed the combined effect of OBFX and FOM in an attempt to determine efficacy against infections caused by S. Dublin and S. Typhimurium. The checkerboard method was used to examine the combined in vitro effect of OBFX and FOM. Fractional inhibitory concentration (FIC) indices of OBFX-FOM combinations against 5 strains of S. Dublin and S. Typhimurium ranged from 0.313 to 1.03, suggesting that the combined effects of these 2 agents are additive or synergistic. The effects of the 2 agents were additive or synergistic in 88.2% of all FIC indices. In time-killing experiments, the combined effects of OBFX and FOM on 2 strains of S. Dublin were found to be synergistic
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