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G. N. Alberti, J. E. Ellis, D. S. Zumbro, R. G. Lane, M. J. Goff; Incidence of Iatrogenic Moxifloxacin Resistance with Intravitreal Injection. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6054.
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The safety and effectiveness of intravitreal anti-angiogenic therapy in the treatment of wet age-related macular degeneration has been proven in multiple collaborative studies. With its widespread acceptance and increasing use, infection risks become more important. Fintak et al demonstrated an endophthalmitis rate of 0.02% in patients receiving intravitreal injections.Prophylactic antibiotics are routinely administered perioperatively to reduce the risk of endophthalmitis. Moxifloxacin is a commonly prescribed antibiotic, however there is little to no data guiding its prophylactic use in intravitreal injection. This study aims to determine whether moxifloxacin provides appropriate coverage based on resistance rates from cultured conjunctival swabs, and if its widespread use might be contributing to increasing resistance rates.
After informed consent was obtained, patients undergoing routine intravitreal injections of either bevacizumab or ranibizumab for wet macular degeneration were recruited into the study. Topical anesthesia was administered with one drop of sterile 0.5% Tetracaine (Bausch & Lomb). The lower conjunctival fornix was then swabbed prior to iodine administration and intravitreal injection. Swabs were sent to the microbiology lab for culture and sensitivity testing using antimicrobial discs.
55 cultures have been performed thus far. Of the 55 cultures, 35 were positive. In decreasing incidence, positive cultures grew: Coagulase-negative staph (94%); Gram-positive cocci (9%); Corynebacterium (9%); Staph Aureus (6%); Enterococcus (3%); and H. Influenzae (3%). 19 out of the 35 cultures were found to be resistant to moxifloxacin. The average number of prior injections in the moxifloxacin-resistant specimens was 10.33, compared to 7.13 in the non-resistant isolates. This difference was statistically significant using a t-test at an alpha of 0.1 (p=0.09).
We encountered a higher than expected rate of moxifloxacin resistance in our study group (54%). There was also a trend for higher resistance rates in patients who had a higher number of previous injections. In one patient, who received injections in both eyes 6 weeks apart, both eyes were initially sensitive to moxifloxacin, and on follow up injections 6 weeks later both eyes grew out resistant coag negative staph. These results raise questions on whether resistance is being induced in patients undergoing intravitreal injections, and whether moxifloxacin provides appropriate perioperative antimicrobial coverage in these patients.
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