Eye Antibiotics Can Cause Drug-Resistant Bacteria: Study

MONDAY Sept. 12, 2011 -- Repeated use of antibiotics among patients who receive eye injections for such ophthalmic conditions as age-related macular degeneration can lead to the emergence of drug-resistant germs, according to a new study.

More than eight million people in the United States are affected by age-related macular degeneration, and its treatment involves monthly injections that are typically followed by antibiotics to prevent such complications as inflammation of the eye.

Researchers from Vanderbilt University School of Medicine in Nashville found, however, that long-term use of antibiotics after eye injection therapy may promote the growth of hard-to-treat germs.

"Repeated exposure of ocular flora [microbes living on or inside the body] ... may select for resistant bacterial strains and cultivate 'superbugs' with multiple-drug resistance ..." the study's authors wrote a news release from Archives of Ophthalmology, which published the results Monday in its September issue.

In conducting the study, the researchers followed 24 patients receiving monthly eye injections in just one of their eyes for at least four months in a row. Each patient was given one of four antibiotics to use following their injection. After each treatment, the researchers cultured, or looked for bacteria, on the surface and the inner lid of both the treated and non-treated eyes.

The bacteria the researchers found was analyzed and tested to determine how vulnerable it was to 16 different antibiotics.

The study found that ongoing exposure to certain antibiotics (fluoroquinolones and azithromycin) was associated with the growth of drug-resistant bacteria, known as coagulase-negative staphylococci (CNS).

Specifically, 81.8 percent of CNS samples taken from treated eyes appeared resistant to at least three antibiotics, and 67.5 percent appeared resistant to at least five antibiotics.

The researchers concluded that repeated use of eye antibiotics leads to CNS resistance to certain antibiotics. As a result, they said, doctors and patients should be more cautious about how eye antibiotics are prescribed and used to avoid the spread of drug-resistant bacteria.

More information

The U.S. National Institutes of Health provides more information on antibiotics.

Posted: September 2011


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