Bacterial Resistance in Patients Receiving Post-Intravitreal Injection Antibiotics

Overview

1. Background: Over 1 million intravitreal injections are performed annually in the United States. The most devastating complication related to these injections is endophthalmitis, with an incidence of 0.02 - 0.1% per injection. Techniques aimed at prevention of this complication have been studied, though emergence rates of antibiotic resistant bacteria in a single clinic population comparing antiseptic technique with iodine vs. use of post-injection second generation fluoroquinolones has not been reported in the literature. 2. Objectives: The purpose of the study is to help determine the best way to prevent infection and limit antibiotic resistance in patients receiving eye injections. 3. Procedures Involved (Research Interventions): After the patient is chosen based on inclusion criteria and agrees to participate in the study, exclusion criteria will be reviewed, cognizance will be determined, informed consent and HIPAA compliance forms will be signed. At this point and prior to the instillation of ophthalmic medications, a Rayon swab will be passed along the inferior fornix of the study eye while the patient looks up and the examiner lowers the lower eyelid. The swab will then be used to inoculate chocolate agar and a blood agar culture plates and a glass slide. These will be brought to the FMO microbiology department for culture and Gram stain. All Staphylococcus aureus and coagulase negative Staphylococcus species identified will be subjected to sensitivity testing using the Gram Positive antibiotic panel available at Loma Linda, with the addition of ciprofloxacin.

Previous studies have demonstrated that bacteria in the eye may become resistant to antibiotics used after injections when compared to the bacteria found in untreated eyes. However, no study published to date compares resistance rates in eyes where an iodine-based preparation is used, which is standard of care, to those in which an antibiotic is also given after the injection in a single practice setting. This is an important issue, because resistant bacteria can cause infections that are more damaging and difficult to treat than non-resistant bacteria. Moreover, previous studies have focused on the emergence of resistance to fourth generation fluoroquinolones including moxifloxacin and gatifloxacin, though use of second generation fluoroquinolones is still practiced in the United States by some retina specialists, including at the investigators institution. Currently in the United States, 81% of retina specialists give antibiotics after eye injections, although the results of several large studies suggest that this practice does not reduce rates of endophthalmitis compared with use of iodine alone.