Comparative Minimal Inhibitory and Mutant Prevention Concentration of Eight Antimicrobial Agents Against .

With the emergence of multidrug-resistant and pan-resistant strains, () shows higher treatment failure rates and mortality in clinics. It is more important to develop an effective method for treating infections. The main objectives of this study were to determine the minimal inhibitory concentration (MIC) and the mutant prevention concentration (MPC) for eight antimicrobial agents against isolated from different hosts and compare the emergence of resistant mutants between animal strains and human strains. A total of 72 nonduplicate isolates and 8 antimicrobial agents (amikacin, azithromycin, levofloxacin, doxycycline, nitrofurantoin, colistin, tigecycline, and imipenem) were used. The MIC and MPC values were determined using agar plate assays. The values of the selection index (SI) were calculated with MPC/MIC. Pharmacodynamic parameters were calculated using published plasma pharmacokinetic variables. For human isolate strains, the MPC (μg/mL) values were as follows: amikacin, 32/128; azithromycin, 64/128; levofloxacin, 4/16; doxycycline, 32/32; nitrofurantoin, 128/512; colistin, 4/8; tigecycline, 8/16; and imipenem, 4/8. The value of SI was 8 for azithromycin, doxycycline, and tigecycline; 16 for amikacin, levofloxacin, and nitrofurantoin; 4 for imipenem; and 2 for colistin. For animal isolate strains, the MPC values were 128 μg/mL for azithromycin and doxycycline, 64 μg/mL for amikacin, 32 μg/mL for levofloxacin, 512 μg/mL for nitrofurantoin, 8 μg/mL for colistin and tigecycline, 4 μg/mL for imipenem. The value of SI was 2 for colistin and imipenem, 8 for tigecycline, 16 for amikacin, and 32 for the other four agents. In combination with pharmacokinetic parameters, these findings indicated that the plasma concentrations of the seven antibiotics except imipenem were below the MPC for the entire dosing interval. The ability of eight antibiotics to prevent resistant mutants of was different between animal strains and human strains. Higher doses than those currently approved should be required to prevent the enrichment of mutants of drug-resistant bacteria in the clinics.