Effects of Intravitreal Anti-VEGF Therapy on Conjunctival Flora and Antibiotic Resistance in Age-Related Macular Degeneration

Background: Age-related macular degeneration (AMD) is a leading cause of visual impairment among older adults. Intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents are widely used for neovascular AMD; however, their potential effects on the conjunctival microbiota remain poorly understood. This study evaluated the impact of intravitreal anti-VEGF therapy on conjunctival microbial composition and antimicrobial resistance patterns. Materials and Methods: Ninety patients with AMD were enrolled and assigned to three groups: bevacizumab-treated (n = 30), aflibercept-treated (n = 30), and untreated dry-type AMD controls (n = 30). Conjunctival swab samples were collected two months after the last injection in treated patients and during routine examination in controls. Bacterial identification and antimicrobial susceptibility testing were performed using automated microbiological systems. Results: Culture positivity rates were comparable among groups, although a lower growth rate was observed in the bevacizumab group (83.3%) than in the aflibercept and control groups (100% each). Staphylococcus epidermidis was significantly more prevalent in both treatment groups than in controls (p = 0.014). Most other bacterial species were detected more frequently in controls. Levofloxacin resistance among staphylococcal isolates was significantly higher in the aflibercept group (p = 0.007), whereas erythromycin and fusidic acid resistance were significantly higher in controls (p = 0.040 and p = 0.001, respectively). Resistance in treated eyes was predominantly associated with S. epidermidis and S. hominis. Conclusions: Intravitreal anti-VEGF therapy may be associated with transient alterations in conjunctival microbiota composition and antimicrobial resistance patterns. These findings may have implications for infection prevention in patients undergoing repeated intravitreal injections.