Common Treatments Can Lead to Antibiotic Resistance

According to a study released this week in the Archives of Ophthalmology, ophthalmologic antibiotics promote antimicrobial resistance too, prompting a call from Vanderbilt Eye Institute physicians to be more judicial in the administration of certain classes of antibiotics.

“The use of topical antibiotics is promoting antimicrobial resistance, prompting an emergence of resistant strains,” said Stephen Kim, M.D., assistant professor of Ophthalmology and Visual Sciences. “This finding is very important for all practicing physicians to be aware of and understand. This information is broadly applicable to everyone.

“This is the first perspective study looking at this, and we were able to convincingly show cause and effect. There needs to be more rational thought when using topical antibiotics.”

Intravitreal injections are the fastest growing procedure in ophthalmology.

In 2008 there were more than 1 million injections performed in the United States, and this number is rising exponentially.

As intraocular injection rates soar, the number of post-injection eye infections (endophthalmitis) will also undoubtedly increase.

Consequently, there has been a dramatic increase in the routine use of topical antibiotics after intravitreal injections in order to reduce endophthalmitis, which is the most devastating complication of intravitreal injections and can result in severe and permanent vision loss.

Aware of this increasing trend of antibiotic use, Kim and colleagues at VEI studied 24 patients undergoing intravitreal injection treatments for macular degeneration. As part of the “Antibiotic Resistance of Conjunctiva and Nasopharynx Evaluation” (ARCaNE) study, patients were randomly assigned to one of four ophthalmic antibiotics to be used after each injection in the treated eye only. The patient’s other eye was not exposed to antibiotics and served as a control.

Patients were followed for one year. Prior to the first injection, all patients underwent baseline conjunctival cultures of both eyes.

During the study period, repeated cultures were taken in both eyes post injection, as well as in the nasopharynx on the same side of the treated eye.

Kim wanted to determine if there were changes in patterns of antibiotic susceptibility of the conjunctival and nasopharyngeal flora after repeated exposure to antibiotics.

“Usually when someone puts in an eye drop, 40 percent of that drop goes into the nasopharnyx,” explained Kim. “The nasopharnyx is host to many different specious and strains of bacteria, some of which can directly cause life-threatening infections such as pneumonia and sepsis.

“Alternating resistance patterns of bacteria in the nasopharnyx may result in more treatment resistant infections.”

According to Kim, topical ophthalmic antibiotics may select for resistant strains in the eye and nasopharnyx and promote the emergence of superbugs with resistance to multiple antibiotics.

“This may have deleterious consequence on our ability to treat future infections,” Kim said.

Preliminary findings from the study were reported in the December 2010 issue of Ophthalmology, which showed substantial baseline resistance patterns.