Assay System for Antimicrobial Concentration of Drugs against Intracellular Legionella Pneumophila / 中山大学学报(医学科学版)

ABSTRACT

[Objective]To explore the intracellular antimicrobial activities of erythromycin,ciprofloxacin,levofloxacin,moxifloxacin against Legionella pneumophila.[Methods]The minimum inhibition concentration(MIC)of each antibiotic was evaluated by E-test method and microdilution method respectively.The minimal extracellular concentration inhibiting intracellular multiplication(MIEC)of each antibiotic was evaluated by the MTT colorimetric assay system.[Results]The MIC concentration for each drug by E-test method wereerythromycin,0.047 μg/mL;ciprofloxacin,0.38 μg/mL;levofloxacin,0.125 μg/mL;moxifloxacin,0.125 μg/mL,the MIC concentrations for each drug by microdilution method wereerythromycin,0.125 μg/mL;ciprofloxacin,0.03 μg/mL;levofloxacin,0.016 μg/mL;moxifloxacin,0.016 μg/mL.The MIEC concentration for each drug wereerythromycin,0.25 μg/mL;ciprofloxacin,0.016 μg/mL;levofloxacin,0.016 μg/mL;moxifloxacin,0.004 μg/mL.[Conclusions]Fluoroquinolones have superior activity than erythromycin in U937 cells infected with L.pneumophila.Moxifloxacin is the most potent drug among the four tested antimicrobials.Our results indicated that the MTT assay system allows comparative and quantitative evaluations of the intracellular activities of antibiotics against L,pneumophila and efficient processing of a large number of samples.