Antibacterial activities of gemifloxacin, levofloxacin, gatifloxacin, moxifloxacin and erythromycin against intracellular Legionella pneumophila and Legionella micdadei in human monocytes.
OBJECTIVE
The antibacterial activity of a new fluoroquinolone, gemifloxacin, was tested against intracellular Legionella pneumophila and Legionella micdadei and was compared with the activities of levofloxacin, gatifloxacin, moxifloxacin and erythromycin.


METHODS
For intracellular assays, bacteria were used to infect human monocyte-derived macrophages prepared from heparinized blood of healthy volunteers. Antibiotics were added following phagocytosis. Numbers of viable bacteria were determined at 0, 24, 48, 72 and 96 h.


RESULTS
The intracellular antibacterial activity of gemifloxacin was concentration- and time-dependent. All of the quinolones had similar activities against L. pneumophila and L. micdadei at 10 x MIC, but there were minor differences: at 24 h moxifloxacin was significantly more active than the other quinolones against L. pneumophila, while gemifloxacin was more active against L. micdadei (P < 0.01). All of the quinolones were markedly more active than erythromycin (P < 0.01). The antibacterial effect of gemifloxacin against L. pneumophila following drug removal at 24 h persisted for 72 h at 20 x MIC but not at 10 x MIC, while for L. micdadei the antibacterial effect persisted for 24 h at 10 x MIC.


CONCLUSIONS
All of the quinolones had similar activities against intracellular L. pneumophila and L. micdadei and were markedly more effective than erythromycin.
Baltch
Aldona L
AL
Infectious Disease Section, Stratton VA Medical Center, Albany, NY 12208, USA. aldona.baltch@med.va.gov
Bopp
Lawrence H
LH
Smith
Raymond P
RP
Michelsen
Phyllis B
PB
Ritz
William J
WJ
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001372:Aza Compounds / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004917:Erythromycin / Q000494:pharmacology; D024841:Fluoroquinolones / Q000494:pharmacology; D000077734:Gatifloxacin; D000077735:Gemifloxacin; D006801:Humans; D007875:Legionella / Q000187:drug effects*; D016952:Legionella pneumophila / Q000187:drug effects*; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D009000:Monocytes / Q000382:microbiology*; D000077266:Moxifloxacin; D009287:Naphthyridines / Q000494:pharmacology; D015242:Ofloxacin / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D009287:Naphthyridines; D011804:Quinolines; D004917:Erythromycin; D064704:Levofloxacin; D015242:Ofloxacin; D000077734:Gatifloxacin; D000077735:Gemifloxacin; D000077266:Moxifloxacin