In Vitro Antimicrobial Susceptibility of Common Bacterial Keratitis Pathogens to Topical Ophthalmic Fluoroquinolones
Arabella R. Mendoza, MD, Eleonore B. Iguban, MD
Department of Ophthalmology, Rizal Medical Center, Philippines
Correspondence: Arabella R. Mendoza, MD, DPBO
Office Address: Rizal Medical Center, 425 Pasig Boulevard, Pasig City, Philippines
Office Phone Number: +639279873613
Email: arramendozamd22@gmail.com
Disclosures: The authors report no conflict of interest.
ABSTRACT
Objective: This study determined the in vitro susceptibility of three bacterial isolates, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae, to 11 commercially available topical ophthalmic fluoroquinolones: levofloxacin (Oftaquix and Leeflox), ofloxacin (Ofbeat and Inoflox), moxifloxacin (Vigamox and Vistamox), besifloxacin (Besivance), ciprofloxacin (Ciloxan and Celsus), and gatifloxacin (Zymar and Agatiflox).
Methods: Zones of inhibitions in millimeters (mm) were obtained for the three bacterial isolates to assess antimicrobial activity. One-way analysis of variance was used to determine differences in antimicrobial sensitivity among treatment groups. T-test was used to detect significant differences between the innovator and the locally produced topical fluoroquinolones.
Results: The three bacterial isolates were sensitive to all 11 topical ophthalmic fluoroquinolones. Ciprofloxacin (Ciloxan and Celsus) produced the largest zones of inhibition for P. aeruginosa isolates. Moxifloxacin (Vigamox and Vistamox) produced the largest zones of inhibition for S. aureus and S. pneumoniae isolates. Significant statistical differences were observed between the innovator ciprofloxacin (Ciloxan) and the locally manufactured ciprofloxacin (Celsus) when tested against P. aeruginosa, as well as between the innovator moxifloxacin (Vigamox) and the locally manufactured moxifloxacin (Vistamox) when tested against S. aureus (p<0.05). The rest of the topical ophthalmic fluoroquinolones showed no statistically significant differences between the locally manufactured and innovator brands.
Conclusion: Although all the tested topical ophthalmic fluoroquinolones showed significant antimicrobial sensitivity in vitro against P. aeruginosa, S. aureus, and S. pneumoniae, some of them demonstrated better antimicrobial activity towards certain organisms. Thus, it is still recommended to determine the etiology of the bacterial keratitis to optimize therapeutic management strategies. Moreover, innovator brands of moxifloxacin and ciprofloxacin were found to be superior in terms of antimicrobial activity compared to locally manufactured brands against particular bacterial pathogens. This may influence treatment response and outcomes, particularly when dealing with keratitis caused by S. aureus and P. aeruginosa.
Keywords: bacterial keratitis, fluoroquinolones, antibacterial susceptibility, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae.