The administration of short courses of topical antibiotic drops before and/or after intravitreal injections is a common practice, but increasing evidence suggests this may not lower the risk of infectious endophthalmitis and could increase rates of antimicrobial resistance. The purpose of the present study is to determine the antimicrobial resistance profiles in patients who have received numerous (≥ 20) courses of antibiotics for intravitreal injection compared with untreated controls.

This study compares 20 control patients without prior intravitreal injection to 20 patients who have undergone ≥ 20 prior intravitreal injections accompanied by a course of topical antibiotics for two days before and/or after the injection procedure. The lower, inner eyelid and nasal cavity were cultured and evaluated via disk diffusion method for antimicrobial sensitivity.

Before administration of anti-VEGF therapy (Vascular Endothelial Growth Factor) or topical antibiotics, conjunctival and nasopharyngeal swabs are procured with the Bacti-Swab transport system (Thermo Fisher Scientific, Waltham, MA). For conjunctival samples, a sterile swab is moistened with ophthalmic balanced salt solution and gently swept along the lower fornix from the medial to the lateral canthi, with all attempts to avoid the eyelashes and eyelids. For nasopharyngeal cultures, the sterile swab is inserted 2 cm into the naris and rotated against the anterior nasal mucosa for 3 seconds.

Culture swabs are then plated onto 5% sheep blood plates and incubated at 37°C for 3 days. Colonies are isolated and identified with API (Analytical Profile Index) Microbial Identification Kits (bioMérieux Inc., Hazelwood, MO). Antibiotic susceptibility is determined using the Kirby Bauer disc diffusion method. Additional data collected includes age, ocular and systemic medical conditions, and the number of intravitreal injections along with anti-VEGF agents used.

Statistical calculations for antibiotic resistance comprises of t-test and and multivariate analysis.

Inclusion Criteria:

• Adult patients (above age 18) diagnosed with age-related macular degeneration and receiving their 1st or 20th (or >20th) intravitreal injection therapy.

Exclusion Criteria:

• Those with current use of topical or systemic antibiotics and an active ocular infection or ocular surface disease.

Outpatient setting