• Are Topical Antibiotics Necessary for Intravitreal Injections?

    With intravitreal injection (IVTI) surpassing cataract surgery as the most common ophthalmic procedure in 2010, it is projected that the number of injections in the United States will approach 6 million in 2016. A survey by the American Society of Retina Specialists suggests that over 90% of ophthalmologists use antibiotics after IVTIs.

    It is estimated that more than 96% of cataract surgeons use antibiotics, based on the rationale that the vitreous is more vulnerable to infection than the anterior chamber. In contrast to cataract surgery, however, IVTIs are not a one-time procedure—but are performed repeatedly, producing multiple exposures to antibiotics. According to Stephen J. Kim, MD, there is no justification for routine use topical ophthalmic antibiotics in the setting of IVTIs. “There is no evidence that such a practice reduces rates of endophthalmitis,” he said.

    Does the use of topicals for IVTI promote resistance? Dr. Kim discussed how the routine practice of short-term and repeated exposure of ocular and nasopharyngeal flora to topical antibiotics may select for drug-resistant bacterial strains. He described the result of 2 studies during the Sunday symposium on drug resistance.

    Dr. Kim was an investigator in a small randomized controlled longitudinal study designed to investigate possible changes in antibiotic resistance patterns after repeated exposure of ocular and nasopharyngeal flora to topical antibiotics in patients receiving IVTIs for choroidal neovascularization. Patients were randomized to 1 of 4 antibiotics: ofloxacin, azithromycin, gatifloxacin, or moxifloxacin. At baseline, substantial levels of resistance were already present in ocular and central nervous system isolates, which further increased during the course of the study.

    A distinct pattern. Interestingly, a distinct pattern also emerged. Subjects who received topical fluoroquinolones developed an increasing resistance to third- and fourth-generation fluoroquinolones, as well as an alarming resistance to macrolides, Dr. Kim said. On the other hand, subjects randomized to azithromycin showed an increasing resistance to macrolides but a decreasing resistance to fluoroquinolones.

    A growing resistance
    . In a separate controlled longitudinal study, Dr. Kim demonstrated that conjunctival Staphylococcus epidermidis repeatedly exposed to fluoroquinolone or azithromycin antibiotics rapidly develop resistance. At baseline, approximately 24% of isolates from control eyes were sensitive to all 16 antibiotics studied, compared just with 3% from treated eyes (p < .01). In addition, 69% and 90% of isolates from control and treated eyes, respectively, were resistant to 3 or more antibiotics. A small percentage of isolates were also resistant to 8, 9, or 10 varieties of antibiotics.

    Dr. Kim cautioned that the overuse of antibiotics promotes bacterial resistance, which is a major public health concern for our patients. “Better antibiotic stewardship is in all of our best interest,” he concluded.—Keng Jin Lee

    Financial disclosures. Dr. Kim: None.