MONDAY, April 11 (HealthDay News) -- Long-term use of antibiotics to treat acne doesn't seem to spur bacteria into becoming resistant to the medications, a new study finds.
The finding came as a bit of a surprise, since widespread use of antibiotics has been credited with encouraging antibiotic resistance in bacteria generally.
Researchers at the University of Pennsylvania School of Medicine assessed the prevalence of Staphylococcus aureus bacteria on 83 patients treated for acne. Some of the patients were using antibiotics while others were not using the drugs.
"While S. aureus colonizes the skin, it can also be responsible for localized cutaneous [skin] infections and life-threatening systemic infections," the study authors wrote in a journal news release.
"At one time, it was sensitive to many antibiotics and antimicrobial agents," they said. "However, because of its ability to adapt to these therapies and become resistant, clinical scenarios now exist in which few therapeutic options remain to treat this organism. Therefore, methicillin-resistant S. aureus (MRSA) has become commonplace."
The researchers found that 36 of the acne patients were colonized with S. aureus. Two of those 36 patients had MRSA; 20 had S. aureus solely in their throats; one-quarter had S. aureus only in their noses, and seven had it in their noses and throats.
"Long-term use of antibiotics decreased the prevalence of S. aureus colonization by nearly 70 percent," the researchers wrote. "A decreased rate of colonization was noted with the use of both oral and topical antibiotics."
Surprisingly, "fewer than 10 percent of the isolates of S. aureus were resistant to tetracyclines, the most commonly used antibiotic family to treat acne," they continued. "Resistance to [the antibiotics] erythromycin and clindamycin was mostly prevalent among our isolates and was noted in the patients who did and did not use antibiotics."
The findings contradict current beliefs about long-term use of antibiotics, the researchers said.
One expert concurred with the findings.
"The results of the study correlate well with our experience minimal to no general bacterial resistance," said Dr. Doris Day, a dermatologist at Lenox Hill Hospital in New York City. "However, our greater concern is that the long term use of tetracycline's and other antibiotics used to treat acne can lead to resistance of the specific bacteria that is the underlying culprit in most cases of acne, which is the P. acnes bacteria."
"For this reason we often pair the antibiotic with a topical benzoyl peroxide, and most of the time we limit the course of treatment to a maximum of 3-4 months when possible," she said.
The study, published online April 11, appears in the August print issue of the journal Archives of Dermatology.
The American Academy of Dermatology outlines prescription medications for acne.
-- Robert Preidt
SOURCE: Doris Day, MD, dermatologist, Lenox Hill Hospital, New York City; JAMA/Archives journals, news release, April 11, 2011
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