title: [Activity of macrolides and fluoroquinolones against intracellular Legionella pneumophila].
abstract: OBJECTIVE
  To evaluate the activity of macrolides and fluoroquinolones against Legionella pneumophila by intracellular susceptibility testing.
  
  
  METHODS
  Minimum inhibitory concentration (MIC) was determined by standard agar dilution test according to the CLSI. For intracellular assays, legionella pneumonia was used to infect human monocytic cell line THP-1. Erythromycin, azithromycin, levofloxacin and moxifloxacin at 1 × MIC, 4 × MIC, 8 × MIC were added following phagocytosis. Number of viable bacteria was enumerated at 24 h on BCYE (buffered charcoal yeast extract) agar in duplicates using standard plate count method. The result was expressed as percentage inhibition. Mann-Whitney U test was used to determine the significant differences in mean percentage inhibition between agents.
  
  
  RESULTS
  Percentage inhibition at 24 h were as follows: Erythromycin 1 × MIC (50.18 ± 27.29)%, 4 × MIC (79.48 ± 20.08)%, 8 × MIC (91.46 ± 8.70)%; Azithromycin 1 × MIC (66.77 ± 26.18)%, 4 × MIC (91.73 ± 8.72)%, 8 × MIC (97.10 ± 3.37)%; Levofloxacin 1 × MIC (99.84 ± 0.25)%, 4 × MIC (99.99 ± 0.02)%, 8 × MIC (99.99 ± 0.01)%; Moxifloxacin 1 × MIC (99.90 ± 0.10)%, 4 × MIC (99.99 ± 0.03)%, 8 × MIC (99.99 ± 0.03)%. The fluoroquinolones showed greater inhibitory activity than macrolides against legionella pneumophila(u = 1.0, 2.0, 5.0, P < 0.05). Levofloxacin and moxifloxacin had the same intracellular activity against legionella pneumophila (u = 190, 183, 217, P > 0.05). Azithromycin was more effective than erythromycin in inhibiting intracellular legionella pneumophila (u = 132, 125, 128, P < 0.05).
  
  
  CONCLUSIONS
  The fluoroquinolones were more active than macrolides against legionella pneumophila. The intracellular activity of levofloxacin against legionella pneumophila appeared to be similar to moxifloxacin. Azithromycin was demonstrated to have superior activity against legionella pneumophila compared with erythromycin.
authors.affiliation: Department of Respiratory, Zhongshan Hospital Affiliated of Fudan University, Shanghai 200032, China.
authors.forename: Ling-ling
authors.initials: LL
authors.lastname: Yu
authors.forename: Bi-jie
authors.initials: BJ
authors.lastname: Hu
authors.forename: Sheng-lei
authors.initials: SL
authors.lastname: Huang
authors.forename: Zhao-yan
authors.initials: ZY
authors.lastname: Zhou
authors.forename: Li-li
authors.initials: LL
authors.lastname: Tao
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002460:Cell Line; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D016952:Legionella pneumophila / Q000187:drug effects*; D018942:Macrolides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009000:Monocytes / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D018942:Macrolides