Comparison of azithromycin and moxifloxacin against bacterial isolates causing conjunctivitis.
OBJECTIVE
To examine in vitro resistance to azithromycin and moxifloxacin in bacterial conjunctivitis isolates.


METHODS
MIC90s (Minimum Inhibitory Concentration) and resistance rates to azithromycin and moxifloxacin were determined based upon microtiter broth dilution and/or antimicrobial gradient test strips in a multicenter phase III study and confirmed externally.


RESULTS
The most common isolates collected from bacterial conjunctivitis patients in the phase III study were Haemophilus influenzae (40.6%), followed by Staphylococcus epidermidis (19.3%), Propionibacterium acnes (17.3%), Streptococcus pneumoniae (16.8%), and Staphylococcus aureus (0.06%). MIC90s for all of these organisms were well below established resistance breakpoints for moxifloxacin, indicating no bacterial resistance. On the other hand, the MIC90 for H. influenzae was 3-fold higher than the resistance breakpoint for azithromycin, > or = 128-fold higher for S. epidermidis, 16-fold higher for S. pneumoniae and > or = 128-fold higher for S. aureus, indicating moderate to very high bacterial resistance to azithromycin.


CONCLUSIONS
Resistance to azithromycin is more common than resistance to moxifloxacin in clinical isolates causing bacterial conjunctivitis.
Ohnsman
Christina
C
Wills Eye Institute, Philadelphia, PA, USA. cohnsman@comcast.net
Ritterband
David
D
O'Brien
Terrence
T
Girgis
Dalia
D
Kabat
Al
A
D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001372:Aza Compounds / Q000627:therapeutic use*; D017963:Azithromycin / Q000627:therapeutic use*; D003234:Conjunctivitis, Bacterial / Q000188:drug therapy* / Q000382:microbiology; D024841:Fluoroquinolones; D006801:Humans; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D011804:Quinolines / Q000627:therapeutic use*
D000900:Anti-Bacterial Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D011804:Quinolines; D017963:Azithromycin; D000077266:Moxifloxacin