Analysis of topical conjunctival microbiotic cultures in patients treated with intravitreal injections using antibiotic prophylaxis with 0.3% ofloxacin eye drops.

Background: Intravitreal injections, a relatively recent treatment in ophthalmology, is being adopted rapidly worldwide and becoming one of the most common therapies in the field. Numerous complications are associated with this treatment, ranging from minor inflammatory ailments to endophthalmitis. We analyzed the conjunctival flora of patients treated with intravitreal injections and topical antibiotics.

Methods: The study was a longitudinal prospective analysis of cultures and antibiograms collected from patients who underwent intravitreal injections and topical antibiotics afterwards at the retina clinic in ABC's Medical University.

Results: A total of 148 swabs obtained from 98 patients were cultured and underwent antibiotic sensitivity testing. All bacteria were sensitive to vancomycin, and with the exception of Escherichia coli samples, they were also sensitive to a third-generation cephalosporin (ceftriaxone-same class and generation as ceftazidime), both of which are important antibiotics for the treatment of endophthalmitis. The bacteria species were specifically coagulase-negative Staphylococcus sp. 92% of which was penicillin-resistant and 56.9% was resistant to ciprofloxacin, a second-generation fluoroquinolone. The culture results were similar to that described in the literature and showed the same higher prevalence of coagulase-negative Staphylococcus sp. and S. epidermidis. Regarding the antibiotic resistance profiles, vancomycin, a third-generation cephalosporin, and penicillin showed almost identical results to those reported previously. Regarding fluoroquinolones, the incidence of resistant coagulase-negative Staphylococcus sp. was lower than the findings worldwide, but the resistance rates found were: S. aureus (26.7%), S. epidermidis (61.3%), and Staphylococcus sp. (coagulase negative, 56.9%).

Conclusions: The current results showed that the typical conjunctival bacteria had higher resistance to fluoroquinolones (although they were not tested specifically to ofloxacin), suggesting a possible selection of resistant bacteria that should not be taken for granted in clinic. However, the same bacteria did not exhibit cross-resistance in the analysis of vancomycin and third-generation cephalosporins. This real-world, longitudinal, prospective study on conjunctival flora analyzed bacterial resistance profiles and contemporary antibiotic use, offering deeper insights into this subject.