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Published on: April 3, 2016
Fluoroquinolone therapy in a rabbit model of post-LASIK methicillin-resistant Staphylococcus aureus keratitis
Charles L Balzli1, Clare C McCormick, Armando R Caballero
1Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
Purpose:
To develop a rabbit model of post-laser in situ keratomileusis (LASIK) methicillin-resistant Staphylococcus aureus (MRSA) keratitis for studying fluoroquinolone prophylaxis and treatment.
Setting:
Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
Methods:
An MRSA keratitis isolate (5 microL, 500 colony forming units [CFU]) was inoculated underneath a corneal flap. Bacterial growth and pathology were determined by quantitative cultures (CFU) and slitlamp examination, respectively. The effectiveness of commercial moxifloxacin and gatifloxacin formulations was compared in 3 regimens: prophylaxis (4 drops before inoculation), early therapy (single drop hourly from 4 to 9 hours postinfection), and late therapy (single drop hourly from 10 to 15 hours postinfection). Zones of bacterial inhibition to known in vivo antibiotic concentrations were determined.
Results:
Bacteria grew to a maximum of approximately 10(6) CFU/cornea within 10 hours postinfection. The slitlamp examination scores showed pathologic changes beginning 10 hours postinfection and progressed throughout the infection. For prophylaxis, eyes treated with moxifloxacin had significantly fewer CFU than gatifloxacin-treated eyes or untreated controls (both P < or = .0001). During early treatment, the antibiotics were equally effective in reducing CFU relative to untreated controls (P < or = .0001). In late treatment, gatifloxacin and moxifloxacin caused significant reductions in CFU relative to untreated controls (P < or = .0007 and P < or = .0001, respectively). Moxifloxacin produced zones of bacterial inhibition significantly larger than those produced by gatifloxacin.
Conclusions:
Methicillin-resistant S aureus inoculation beneath a rabbit corneal flap produced an infection that was useful for quantitative microbiological studies. A significant advantage in using moxifloxacin relative to gatifloxacin was observed in prophylaxis of keratitis (P = .0001).
Insights
This study developed a rabbit model for post-LASIK (laser in situ keratomileusis) MRSA (methicillin-resistant Staphylococcus aureus) keratitis. Moxifloxacin showed superior efficacy in prophylaxis against MRSA keratitis compared to gatifloxacin.
Area of Science:
- Ophthalmology
- Microbiology
- Pharmacology
Background:
- Post-LASIK (laser in situ keratomileusis) infections, particularly those caused by methicillin-resistant Staphylococcus aureus (MRSA), pose a significant clinical challenge.
- Effective prophylaxis and treatment strategies are crucial for managing MRSA keratitis following refractive surgery.
Purpose of the Study:
- To establish a robust rabbit model for studying MRSA keratitis in the context of post-LASIK surgery.
- To evaluate the efficacy of fluoroquinolone antibiotics, specifically moxifloxacin and gatifloxacin, in prophylaxis and treatment of MRSA keratitis.
Main Methods:
- A rabbit model was developed by inoculating MRSA (methicillin-resistant Staphylococcus aureus) under the corneal flap created by LASIK (laser in situ keratomileusis).
- Bacterial growth was quantified using colony-forming units (CFU), and corneal pathology was assessed via slitlamp examination.
- The efficacy of moxifloxacin and gatifloxacin was compared in prophylactic, early therapeutic, and late therapeutic regimens.
Main Results:
- MRSA keratitis developed within 10 hours post-inoculation, characterized by bacterial growth and progressive corneal pathology.
- Moxifloxacin demonstrated superior efficacy in prophylaxis, significantly reducing CFU compared to gatifloxacin and controls (P < or = .0001).
- Both antibiotics were effective in early and late treatment phases, with moxifloxacin showing larger zones of bacterial inhibition.
Conclusions:
- The developed rabbit model is suitable for quantitative microbiological studies of post-LASIK MRSA keratitis.
- Moxifloxacin offers a significant advantage over gatifloxacin in the prophylaxis of MRSA keratitis.
