Antibiotic resistance against fluoroquinolones is increasing, and that may adversely impact patients with retinal disorders.
The introduction of intravitreal injections (IVT) to treat retinal diseases has increased from about 1 million in 2007 to an expected 6 million in 2016 (up from only 4,000 in 2001).
“The number of injections has rapidly exceeded the number of cataract surgeries performed in the United States,” said Stephen Kim, MD, Vanderbilt Eye Institute, Vanderbilt University, Nashville, TN.
In 2009, the American Society of Retina Specialists surveyed its members and found that 90% used antibiotics at the time of intravitreal injections, and 40% use topical antibiotics before intravitreal injections.1
“There is rationale to support this practice,” Dr. Kim explained. “Antibiotics reduce conjunctival flora. They achieve MIC50 levels in the vitreous—at least the fourth-generation fluoroquinolones do.”
From years of observation in cataract surgery, “we know that the vitreous is more vulnerable to infection than the anterior chamber,” he added. The medicolegal implications at that time compelled retina specialists to use antibiotics when administering injections.
Unlike cataract surgery, IVT treat chronic conditions and are often given repeatedly and sometimes indefinitely, Dr. Kim said. Further, the nasopharynx is exposed to antibiotic after a single-drop application and “many potential pathogens” colonize the nasopharynx of healthy individuals, he added. For example, Dr. Kim noted 30% of people are colonized with Staphylococcus aureus.
“This is the most common cause of nosocomial-acquired pneumonia,” Dr. Kim said. “You can get the sense that repeated, short-term, indefinite use of antibiotics in the setting of IVT could profoundly increase antibiotic resistance.”
It was that potential that drove the initiation of the Antibiotic Resistance of Conjunctiva and Nasopharynx Evaluation Study (ARCaNE study). This is a prospective, randomized, longitudinal study designed to determine changes in antibiotic resistance after repeated exposure of flora, conjunctival, and nasopharyngeal, after repeated antibiotic use in patients undergoing IVT for choroidal neovascularization (CNV).
Inclusion criteria included any person with CNV in one eye only and planned IVT (no specification about which drug to be injected). Among the exclusion criteria were previous IVT in either eye, chronic use of topical medications, contact lens wear, ocular surgery, or use of topical drugs in either eye in the 3 months prior to study enrollment.