Related Experiment Video
Updated: May 31, 2025
Whole Genome Sequencing of Candida glabrata for Detection of Markers of Antifungal Drug Resistance
Published on: December 28, 2017
Antifungal Susceptibility of Dermatophyte Isolates from Patients with Chronic and Recurrent Dermatophytosis
Nikhitha Amin1, Manjunath M Shenoy2, Vidya Pai3
1Department of Dermatology, Yenepoya Medical College and Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, Karnataka, India.
Background:
The widespread occurrence of chronic and recurrent dermatophytosis has significantly affected the quality of life for patients in India and beyond. Identifying the causative dermatophytes and understanding their antifungal susceptibility can aid clinicians in tailoring effective antifungal therapies.
Materials And Methods:
Patients with chronic and recurrent dermatophytosis were enrolled, and conventional fungal cultures were conducted on skin scrapings. Identified isolates underwent antifungal susceptibility testing using the Clinical and Laboratory Standards Institute broth microdilution method (CLSI M38-A2) for common systemic antifungals, determining the minimum inhibitory concentration (MIC) range and calculating MIC 50 and MIC 90.
Results:
Sixty samples were tested. Tinea corporis was the most common presentation (66.6%). Trichophyton mentagrophyte species complex was the prevalent species (45, 75%), followed by Trichophyton rubrum (7, 11.7%). In Trichophyton mentagrophytes species complex, MIC range was 8-64 μg/mL for fluconazole, 0.06-0.25 μg/mL for terbinafine, and 0.125-0.5 μg/mL for griseofulvin. For Trichophyton rubrum, the MIC range was 8-64 μg/mL for fluconazole, 0.06-0.25 μg/mL for terbinafine, and 0.125-0.5 μg/mL for griseofulvin. For all species, itraconazole MIC was ≤0.125 μg/mL. Hence, itraconazole and terbinafine had the best MIC range against tested isolates in our study.
Limitations:
Absence of genotyping of isolate and not compared the results with studies where sequence-based identification to species level was done.
Conclusion:
In vitro, resistance to itraconazole for any of the four isolated agents was not seen. Terbinafine resistance appears to be an uncommon occurrence in South India. In vitro susceptibility tests shall be regularly done to design the epidemiological cutoff values.
Insights
Chronic fungal skin infections are common in India. Itraconazole and terbinafine show excellent in vitro activity against common dermatophytes, suggesting their effectiveness in treating recurrent tinea infections.
Area of Science:
- Medical Mycology
- Dermatology
- Antimicrobial Resistance
Background:
- Chronic and recurrent dermatophytosis significantly impacts patient quality of life globally.
- Identifying causative fungi and their antifungal susceptibility is crucial for effective treatment.
- Understanding local resistance patterns aids in optimizing antifungal therapy selection.
Purpose of the Study:
- To identify prevalent dermatophyte species causing chronic infections in South India.
- To determine the in vitro antifungal susceptibility of these isolates to common systemic antifungals.
- To guide clinical management of dermatophytosis based on antifungal efficacy.
Main Methods:
- Conventional fungal cultures from skin scrapings of patients with chronic dermatophytosis.
- Antifungal susceptibility testing using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method (M38-A2).
- Determination of minimum inhibitory concentration (MIC) ranges, MIC50, and MIC90 for fluconazole, terbinafine, griseofulvin, and itraconazole.
Main Results:
- Trichophyton mentagrophyte species complex (75%) and Trichophyton rubrum (11.7%) were the most common isolates.
- All tested isolates showed favorable minimum inhibitory concentration (MIC) values for itraconazole (≤0.125 μg/mL) and terbinafine (0.06-0.25 μg/mL).
- Fluconazole exhibited higher MICs (8-64 μg/mL) compared to terbinafine and itraconazole.
Conclusions:
- No in vitro resistance to itraconazole was observed among the isolated dermatophytes.
- Terbinafine resistance appears uncommon in South India based on in vitro susceptibility.
- Regular in vitro susceptibility testing is recommended to establish epidemiological cutoff values for dermatophytes.
