Penetration and effectiveness of prophylactic fluoroquinolones in experimental methicillin-sensitive or methicillin-resistant Staphylococcus aureus anterior chamber infections.
OBJECTIVE
To determine the effectiveness of moxifloxacin and besifloxacin prophylactic therapy for experimental Staphylococcus aureus infections originating in the rabbit anterior chamber.


METHODS
Microbiology Department, University of Mississippi Medical Center, Jackson, Mississippi, USA.


METHODS
Experimental study.


METHODS
Minimum inhibitory concentrations (MICs) of moxifloxacin 0.5% and besifloxacin 0.6% for methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains were determined. Eyes were treated with moxifloxacin, a moxifloxacin alternative formulation 0.5%, or besifloxacin (45 μL) 30 minutes or 60 minutes before anterior chamber infection (10(6) colony-forming units [CFUs]). Aqueous humor was removed 30 minutes after infection for quantification of antibiotic and bacteria.


RESULTS
The MIC for both organisms was 0.06 μg/mL for moxifloxacin and 0.03 μg/mL for besifloxacin. In MSSA infections, the untreated eyes contained 5.18 log CFU/mL, which was similar to besifloxacin-treated eyes with either treatment (P≥.1091). Eyes treated with moxifloxacin or moxifloxacin alternative formulation contained significantly fewer CFUs than untreated controls or besifloxacin-treated eyes with either treatment (P≤.0020). The aqueous humor in eyes treated with moxifloxacin or moxifloxacin alternative formulation contained significantly more drug than besifloxacin-treated eyes at both prophylactic time points (P≤.0012). In MRSA infections, the untreated eyes contained 4.91 log CFU/mL, which was similar to besifloxacin-treated eyes with either treatment (P≥.5830). Eyes treated with moxifloxacin or moxifloxacin alternative formulation contained significantly fewer CFUs than untreated controls or besifloxacin-treated eyes at both prophylactic time points (P≤.0008).


CONCLUSIONS
Moxifloxacin had greater in vivo effectiveness against MSSA and MRSA than besifloxacin. The aqueous antibiotic concentrations suggest limited penetration by besifloxacin, accounting for its lack of effectiveness.
Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
Charles L
CL
Balzli
Armando R
AR
Caballero
Aihua
A
Tang
Anastasia C
AC
Weeks
Richard J
RJ
O'Callaghan
D000818:Animals; D000890:Anti-Infective Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D001082:Aqueous Humor / Q000378:metabolism* / Q000382:microbiology*; D001372:Aza Compounds / Q000493:pharmacokinetics / Q000627:therapeutic use; D001381:Azepines / Q000493:pharmacokinetics / Q000627:therapeutic use; D001682:Biological Availability; D003114:Colony-Forming Units Assay; D004195:Disease Models, Animal; D015818:Eye Infections, Bacterial / Q000188:drug therapy* / Q000378:metabolism / Q000382:microbiology; D024841:Fluoroquinolones / Q000493:pharmacokinetics / Q000627:therapeutic use; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D011804:Quinolines / Q000493:pharmacokinetics / Q000627:therapeutic use; D011817:Rabbits; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000378:metabolism / Q000382:microbiology; D016896:Treatment Outcome
D000890:Anti-Infective Agents; D001372:Aza Compounds; D001381:Azepines; D024841:Fluoroquinolones; D011804:Quinolines; C522124:besifloxacin; D000077266:Moxifloxacin