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Updated: Jun 4, 2026
Assay Development for High-Throughput Drug Screening Against Mycobacteria
Published on: October 25, 2024
In vitro activities of retapamulin and 16 other antimicrobial agents against recently obtained Streptococcus pyogenes
Emilio Pérez-Trallero1, Esther Tamayo, Milagrosa Montes
1CIBERES, San Sebastián, Spain. mikrobiol@terra.es
Abstract:
Retapamulin in vitro activity against 400 Streptococcus pyogenes clinical isolates obtained from skin, pharynx, ear fluid, and blood samples recovered from 2007 to 2009 was studied. The isolates belonged to 26 different emm types, including isolates nonsusceptible to erythromycin (n=187), tetracycline (n=99), ciprofloxacin (n=59), and bacitracin (n=43). Results were compared to the activities of 16 other antibiotics for topical and systemic use. Retapamulin MICs ranged from ≤0.015 to 0.12 μg/ml, showing the highest intrinsic activity among the topical antimicrobial drugs studied.
Insights
Retapamulin demonstrated potent in vitro activity against Streptococcus pyogenes, including strains resistant to other antibiotics. This topical antimicrobial drug showed the highest intrinsic activity among those tested.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Antimicrobial resistance in S. pyogenes is a growing concern.
- Novel topical antimicrobials are needed for skin and pharyngeal infections.
Purpose of the Study:
- To evaluate the in vitro activity of retapamulin against clinical isolates of Streptococcus pyogenes.
- To compare retapamulin's activity with other topical and systemic antibiotics.
- To assess retapamulin's efficacy against antibiotic-nonsusceptible S. pyogenes strains.
Main Methods:
- In vitro susceptibility testing of 400 S. pyogenes clinical isolates.
- Determination of minimum inhibitory concentrations (MICs) for retapamulin.
- Comparison of retapamulin's activity against 16 other antimicrobial agents.
- Inclusion of isolates with varying emm types and resistance profiles.
Main Results:
- Retapamulin exhibited potent in vitro activity with MICs ranging from ≤0.015 to 0.12 μg/ml.
- Retapamulin demonstrated higher intrinsic activity than other topical antimicrobials studied.
- Activity was observed against S. pyogenes isolates nonsusceptible to erythromycin, tetracycline, ciprofloxacin, and bacitracin.
Conclusions:
- Retapamulin possesses significant in vitro antimicrobial activity against Streptococcus pyogenes.
- It is a promising topical agent, particularly against strains with existing resistance mechanisms.
- Further clinical evaluation is warranted for retapamulin in treating S. pyogenes infections.
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