In Vitro And In Vivo Studies Of Mutant Selection Window For Klebsiella Pneumoniae

ObjectiveTo measure the Minimum Inhibitory Concentration(MIC) and Mutant Prevention Concentration(MPC) of levofloxacin against the clinical isolates of Klebbsiella pneumoniae in vitro. To establish the mice pulmonary infection model which is aroused by Klebbsiella pneumoniae and determine the related pharmacokinetic/pharmacodynamic (PK/PD) parameters. The effects of drug concentration on the enrichment of resistant mutants degree were observed. In combined with the vitro measurement, to validate the mutant selection window(MSW) theory in animals. The treatment of pneumoniae which is aroused by Klebbsiella pneumoniae was evaluated by the MSW theory and pharmacokinetic parameters.MethodsMIC and MPC of levofloxacin against the clinical isolates of Klebbsiella pneumoniae were determined by standard agar dilution method, calculate the selection index(SI), the Pseudomonas aeruginosa ATCC27853 strain were selected as the quality control. To establish the mice pneumoniae model of Klebbsiella pneumoniae infection by nasal and compare the death of different inoculation doses in order to determine the optimum dose. According to the pulmonary infection model of Klebbsiella pneumoniae, different doses levofloxacin were given in oral. To inspect the emergence frequency of different dose group and the changes in MIC after treatment and evaluate the relationship between the different dose group and the amplification of bacteria-resistant mutant strains. The concentration of levofloxacin in blood after treatment one day, three day, five day and seven day were analysized by high-performance liquid chromatographic(HPLC). In combine with the MIC and MPC tested in vitro, evaluate the relationship between the levofloxacin dose in treatment of bacterial infections and effect.ResultsThe MICs and MPCs of clinical isolates of Klebsiella pneumoniae were 0.0625μg/ml and 1μg/ml respectively, the SI was 16. The strain was the levoflozacin susceptible according to the CLSI susceptibility criteria. Three inoculation dose groups were no significant difference in mortality rates. The final inoculation concentration 108CFU/ml and the dose 30μl were determined by considerate the inoculate time,inculate dose and other factors. While given different dose levofloxacin, there were no significantly increased in MICs and the mutation rates were constant in 15mg/kg and 90mg/kg dose groups. In contrast, the mutation rates and MICs were increased significantly in 30mg/kg and 60mg/kg. dose groups. The MIC value of 30mg/kg dose group increased 2-fold in compare with vaccination, while the 60 mg/kg dose group main choose the high levels of mutation and the MIC value increased 8-fold. The results analysised by HPLC indicated that when the plasma drug concentration fall in the MSW most of the time would lead to bacterial resistance mutation rates increase.ConclusionIn the treatment of Klebsiella pneumoniae infection, different doses of levolfoxacin will induce different bacterial mutation rates. If the dose of drug is not inappropriate, it will rise to amplification of mutant bacteria though it can save the life, and transmission within the certain range, increase the difficulty of treatment. So the study recommends that using of the high-dose therapy in the premise of safe when the treatment of bacterial infections.