In vitro antimicrobial analysis of aqueous humor after topical application of moxifloxacin hydrochloride 0.5%

PURPOSE: To evaluate the in vitro antimicrobial activity of aqueous humor in patients who had preoperative topical application of moxifloxacin hydrochloride 0.5%. SETTING: Department of Ophthalmology, Santa Casa de Misericórdia de São Paulo, Brazil. DESIGN: Comparative case series. METHODS: Twenty-nine eyes from 29 cataract surgery patients were included in this study. In the study group (n = 15 eyes), 3 topical applications of moxifloxacin hydrochloride 0.5% were administered preoperatively; in the control group (n = 14 eyes), no topical applications were administered. Aqueous humor samples were collected and stored in sterile microtubes at -80°C until analysis. Antimicrobial analysis was performed using standard strains with standard sterile filter paper disks. Inhibition halos were measured in millimeters, and both bactericidal and bacteriostatic effects were analyzed. RESULTS: Inhibition halos were observed on most of the study group plates except those with Streptococcus pneumoniae: Escherichia coli (13.93 mm ± 0.64 [SD]), Klebsiella pneumoniae (10.63 ± 0.61 mm), Staphylococcus aureus (7.47 ± 0.68 mm), and S epidermidis (4.20 ± 3.33 mm) The differences between the mean inhibition halo diameters were statistically significant (P < .0001) in all samples. No bactericidal effect was observed against any of the microorganisms studied. CONCLUSIONS: After topical application of moxifloxacin 0.5%, aqueous humor showed bacteriostatic effect against E coli, K pneumoniae, S aureus, and S epidermidis. No bactericidal effect was observed against any of the microorganisms evaluated. No antimicrobial effect against S pneumoniae was observed. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.