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Objective: levofloxacin, moxifloxacin single-agent and, respectively, combined cefazolin clinically isolated specimens ciprofloxacin and methicillin-sensitive Staphylococcus aureus mutant prevention concentration (MPC) by measuring the two kinds of fluoroquinolone drugs (FQ) , FQ drugs monotherapy and combination therapy for Staphylococcus aureus MPC90 MPC / MIC (selection index SI) fluoroquinolone combination of Staphylococcus aureus mutant selection window (MSW) in vitro preliminary study for clinical prevention and treatment of bacterial resistance generated to provide a theoretical basis for the use of existing antibiotics. Methods: Using the standard agar dilution method levofloxacin, moxifloxacin, cefazolin minimum inhibitory concentration (MIC) of 30 clinical isolates of Staphylococcus aureus and Staphylococcus aureus control strains ATCC25923 calculate the MIC50 values and MIC90 values. The standard agar dilution method for the determination of the two kinds of FQ anti-drug clinical isolates of Staphylococcus aureus mutation concentration, the first enrichment broth method 1010CFU/ML concentration of gold aureus, take broth the 100μl uniform smear each containing times than dilution containing agar monotherapy and the two drug-containing antimicrobial agents, the total bacterial inoculation amount of the flat plate of each drug concentration is 1.2 × 1010CFU. Incubated at 35 ℃, the lowest concentration of the drug for 72 hours no colony growth of the drug MPC calculation of the drug after a single agent and combination MPC50, MPC90, MPC / MIC. Paired t-test statistical analysis using SPSS statistical software. The results: 1, levofloxacin single-agent MPC range of 30 strains of Staphylococcus aureus in the 2-64 mg / L, joint cefazolin MPC range of 0.5-16 mg / L,. Moxifloxacin single drug 30 Staphylococcus aureus MPC range 0.25-16 mg / L, the United cefazolin MPC range 0.125-4 mg / L, respectively. 2, a single agent levofloxacin levofloxacin 32mg / L, moxifloxacin MPC90 low as 4 mg / L, 30 Staphylococcus aureus MPC90. 3, after the joint cefazolin levofloxacin by a single drug 32mg / L of 30 Staphylococcus aureus MPC90 decreased to 8 mg / L; the MPC90 by the United cefazolin Houmoxisha Star single drug 4mg / L down to 1 mg / L. Statistical t-test p lt; 0.05, with a significant difference. 4, levofloxacin single drug of 30 Staphylococcus aureus MPC90/MIC90 8, after a joint cefazolin MPC90/MIC90 reduced to 2; the drug moxifloxacin single 30 Staphylococcus aureus MPC90/MIC90 4 joint cefazolin MPC90/MIC90 dropped, t test P LT; 0.05, has a significant difference. 5, the combination Houmoxisha star MPC90 1 mg / L, the MPC90/MIC90 1, significantly lower than levofloxacin MPC90 (8 mg / L), MPC90/MIC90 (2). Conclusion: 1, moxifloxacin on clinical isolates of Staphylococcus aureus MPC value low mutant selection window is narrow, better anti mutations, clinical drug resistance, and good security quinolone drugs. 2, levofloxacin and cefazolin associated with MPC reduce, MSW narrow, and reduce moxifloxacin cefazolin combined with MPC, and equal to the MIC. The test results indicate that the combination can narrow mutant selection window, or even shut down the single-agent can reduce the selective enrichment of mutant bacterial resistance amplification to prevent the generation of antimicrobial resistance.
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