Changes in antibiotic resistance patterns of conjunctival flora due to repeated use of topical antibiotics after intravitreal injection.

Abstract

To determine the effect of repeated intermittent use of topical antibiotics after intravitreal injections on conjunctival bacterial flora and antibiotic resistance. Cross-sectional case-control study. A total of 80 eyes of 40 patients were enrolled (40 study eyes, 40 control eyes). Patients were enrolled with unilateral exudative age-related macular degeneration who had received at least 3 prior intravitreal injections with use of postinjection topical antibiotics. Patients had received an average of 7 (range, 3-13) intravitreal injections before enrollment. At the time of enrollment, the inferior fornix of the treated eye was swept with a culture swab before use of povidone iodine; the inferior fornix of the fellow eye was also cultured and served as a control. The culture and sensitivity data from the study and control eyes were analyzed. The rate of antibiotic resistance among the conjunctival bacterial flora of the study eyes and control eyes. A total of 80 eyes of 40 patients were enrolled in the study; 29 patients used trimethoprim/polymyxin B drops, and 11 patients used fluoroquinolone drops after each injection. A total of 58 bacterial colonies were isolated from 50 eyes. There were no significant differences in bacterial species or culture positivity rates between study and control eyes. Coagulase-negative staphylococcus accounted for 41 of the 58 bacterial colonies (71%). There was a 63.6% resistance rate to fluoroquinolones among study eyes compared with 32.1% among control eyes (P < 0.05). In the subset of 11 study eyes using fluoroquinolone drops for 4 days after injection, there was an 87.5% resistance rate compared with 25.0% in matched control eyes (P = 0.04). There was no significant difference in trimethoprim resistance rates between study and control eyes: Four of 14 study eyes (28.6%) showed resistance compared with 5 of 18 control eyes (27.7%) (P = 1.0). Use of fluoroquinolone drops after intravitreal injection leads to increased rates of resistance among conjunctival flora. Repeated use of topical fluoroquinolones after intravitreal injections may have a detrimental effect on eye health by breeding resistance in the bacterial flora.