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.
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