Antibiotic Resistance of Ocular Surface Flora With Repeated Use of a Topical Antibiotic After Intravitreal Injection

Importance: Treatment with intravitreal (IVT) injections has increased during the last several years as evidence has accumulated demonstrating the efficacy of anti-vascular endothelial growth factor agents in the treatment of neovascular age-related macular degeneration (AMD) and various retinal vascular diseases. Although IVT injections are generally safe infectious endophthalmitis is a rare but devastating complication and the risk of morbidity and vision loss from endophthalmitis is high. Objective: To examine the change in antibiotic resistance of ocular surface flora with repeated prophylactic use of antibiotics after IVT injection for AMD. Design and Setting: Prospective nonrandomized cohort study in 2 tertiary academic hospitals. Participants: Patients 65 years and older with newly diagnosed AMD were recruited by 7 retinal specialists from July 1, 2010, through December 31, 2011. Intervention: The study group received topical moxifloxacin hydrochloride for 3 days after each monthly IVT injection. Main Outcome Measure: Resistance to moxifloxacin and ceftazidime in cultured isolates at baseline and monthly for 3 months by change in minimal inhibitory concentration (MIC) of culture isolates was studied. Results: The study group consisted of 84 patients and the control group had 94 patients. In the study group the baseline adjusted MIC increased (from 1.04 to 1.25 mu g/mL; P=.01) as did the MIC for 50% of isolates (MIC50) (from 0.64 to 1.00 mu g/mL) and the MIC for 90% of isolates(MIC90) (from 0.94 to 4.00 mu g/mL). In both groups the culture-positive rate did not change significantly when adjusted for baseline. No significant change was found in the MIC level culture-positive rate MIC50 level and MIC90 level in the control group. Subgroup analysis found diabetes mellitus to be noncontributory to both the MIC and culture-positive rate. No endophthalmitis or adverse events were reported. Conclusions and Relevance: Repeated use of topical moxifloxacin after IVT injection significantly increases antibiotic resistance of ocular surface flora. We recommend that routine use of prophylactic