Fewer than 10% of Staphylococcus aureus isolates showed resistance to long-term use of tetracycline antibiotics in a cross-sectional study of 83 patients with acne. Furthermore, the patients on antibiotics for acne showed a lower prevalence of S. aureus than acne patients not on antibiotics.
Approximately 40% of the S. aureus isolates were resistant to clindamycin and 44.2% to erythromycin, but all other antibiotics tested (trimethoprim-sulfamethoxazole, ciprofloxacin, doxycycline, and minocycline) showed resistance of less than 10%, reported Dr. Matthew Fanelli and his colleagues from the University of Pennsylvania (Arch. Dermatol. 2011 [doi:10.1001/archdermatol.2011.67]).
Thirty-six patients (43%) overall had S. aureus colonies: 5 of 23 (22%) in the oral antibiotics group, compared with 31 of 60 (52%) in the non-antibiotics group.
The colonies were found in the throat (56%), nose (25%), and in both (19%). Two had methicillin-resistant S. aureus (MRSA) in the throat.
Investigators took cultures from both the oropharynx and the anterior nares to assess the effect of the antibiotics on the development of S. aureus and MRSA in the throat and the nose. Across the board, antibiotic resistance was higher in the nasal area than in the throat.
They reported that "[l]ong-term use of antibiotics [to treat acne] decreased the prevalence of S. aureus colonization by nearly 70%."
Long-term use of antibiotics constituted 2 months, instead of the more commonly used 1 month measure, another study author, Dr. David J. Margolis, said in an interview.
Thirty-six patients were using oral or topical antibiotics for acne for at least 1 month before the study. Nine patients had used non-acne antibiotics in the last month.
Of the 51 female and 32 male patients, 63 were white, and median age was 24 years. The majority had an acne severity grade of 2 or 3. The investigators reported that age, sex, Hispanic ethnicity, race, and acne severity did not directly affect S. aureus colonization rates.
"I was surprised by the findings," Dr. Margolis said, noting that the patients were young and fairly healthy, yet they provided the "ideal" group of patients to study for antibiotic resistance.
Antibiotic resistance is a hot topic in the media, and Dr. Margolis expressed concern that media accounts would generalize the study for all antibiotics, instead of just those that address acne.
Study authors reported no relevant financial disclosures. Partial support for the study came from a National Institutes of Health grant.