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Published on: January 3, 2020
Susceptibility of Staphylococcus aureus to topical agents in the United States: a sentinel study
Douglas J Biedenbach1, Samuel K Bouchillon1, Seth A Johnson1
1International Health Management Associates, Inc, Schaumburg, Illinois.
Background:
Mupirocin has been used topically for treating skin and skin structure infections and for nasal decolonization before surgical interventions. Pleuromutilin compounds, including retapamulin, provide similar treatment/interventional options. Rates of resistance of Staphylococcus aureus to mupirocin and other agents used to treat skin and skin structure infections vary between countries and medical centers, including those in the United States. These resistance rates may be associated with higher usage and/or improper epidemiologic practices.
Objective:
This study aimed to determine rates of resistance to topical and other class agents against S aureus isolates collected from SSSIs.
Methods:
Isolates were obtained from outpatients at 6 US dermatology centers in 5 states. Demographic data were collected from medical records, and each patient completed a study questionnaire on recent history of skin infections, antibiotic use, and hospitalization. Each isolate was tested against cephalothin, clindamycin, erythromycin, gentamicin, mupirocin, tetracycline, retapamulin, and trimethoprim/sulfamethoxazole.
Results:
Although methicillin-resistance rates varied between centers (range, 15.8%-35.5%), macrolide resistance was ~50% at all of the sites in this study. Mupirocin-resistant isolates were observed much more frequently from 1 center (33.9%), and nearly all demonstrated high-level resistance. Only 1 retapamulin-resistant isolate (0.5%) was observed, with a minimum inhibitory concentration of 16 µg/mL. The other agents had relatively low resistance rates, which varied between centers and were dependent on susceptibility to methicillin.
Conclusions:
Although the rate of mupirocin-resistant S aureus isolates collected in this investigation was >10%, retapamulin resistance was infrequent. Surveillance of topical agents to determine resistance rates against targeted bacteria is necessary.
Insights
Mupirocin-resistant Staphylococcus aureus is a growing concern, with over 10% of isolates showing resistance. Retapamulin showed infrequent resistance, highlighting the need for ongoing surveillance of topical agents against S. aureus.
Area of Science:
- Dermatology
- Infectious Diseases
- Microbiology
Background:
- Mupirocin and retapamulin are topical agents used for skin infections and nasal decolonization.
- Staphylococcus aureus resistance rates to mupirocin vary globally and within the US.
- Increased usage and improper practices may contribute to rising resistance rates.
Purpose of the Study:
- To determine the resistance rates of Staphylococcus aureus (S. aureus) to topical and other antimicrobial agents.
- To analyze resistance patterns in isolates collected from skin and skin structure infections (SSSIs).
Main Methods:
- Isolates of S. aureus were collected from outpatients at six US dermatology centers.
- Patient data on demographics, infection history, and antibiotic use were gathered.
- Isolates were tested for susceptibility to various agents, including mupirocin and retapamulin.
Main Results:
- Methicillin resistance in S. aureus varied by center (15.8%-35.5%), while macrolide resistance was consistently around 50%.
- Mupirocin resistance was high at one center (33.9%), with most isolates showing high-level resistance.
- Retapamulin resistance was infrequent (0.5%), with one isolate showing reduced susceptibility.
Conclusions:
- Over 10% of S. aureus isolates in this study were resistant to mupirocin.
- Retapamulin demonstrated infrequent resistance, suggesting its potential utility.
- Continuous surveillance of topical antimicrobial resistance in targeted bacteria is essential.
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