Liu, L.G., Zhu, Y.L., Hu, L.F., Cheng, J., Ye, Y. and Li, J.B. (2013) Comparative Study of the Mutant Prevention Concentrations of Vancomycin Alone and in Combination with Levofloxacin, Rifampicin and Fosfomycin against Methicillin-Resistant Stapylococcus epidermidis. The Journal of Antibiotics, 66, 709-712.
ABSTRACT: Objectives: To determine the mutant prevention concentration (MPC) of sulfamethoxazole-trimethoprim (SXT) alone and in combination with levofloxacin (LVX) against Stenotrophomonas maltophilia (S. maltophilia) and to determine if the combination may decrease the emergence of resistant mutants. Methods: The MPC with 20 S. maltophilia strains which were both susceptible to SXT and LVX were determined by inhibiting visible growth among 1010 CFU on four agar plates after 72 hours incubation at 37°C. Results: All except two strains (18/20) showed a mutant prevention concentration ≥ 152/8 μg/mL for SXT and the range of the mutant prevention concentration for the SXT in combination with LVX is 9.5/0.5~608/32 μg/mL, which demonstrates at least 2 fold reduction except one strain. There was a significant difference (P Conclusions: The MPC/MIC values were narrowed for SXT by combining with LVX against the S maltophilia. The combination may decrease the enrichment of mutant bacterial populations. Much study is needed to verify whether the using of drug combinations may restrict or even block the selection of S. maltophilia mutants.