Differential Susceptibility of Terbinafine-Resistant and Sensitive Isolates of the T. mentagrophytes Complex to Cold Atmospheric Plasma

Authors
Fatemeh Hemmatyar 1
Zahra Salehi 2
Seyed Mohammad Atyabi 3
1 Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 Department of Mycology, Pasteur Institute of Iran, Tehran, Iran
3 Department of Nanobiotechnology, Pasteur Institute of Iran, Tehran, Iran
Abstract
Introduction: Trichophyton mentagrophytes is one of the most common dermatophytes in Iran and a major cause of tinea corporis, tinea cruris, and onychomycosis. The increasing emergence of terbinafine-resistant isolates has led to considerable therapeutic challenges and highlighted the need for alternative therapies. Cold atmospheric plasma (CAP) has recently been introduced as a promising antifungal approach. This study reports the effectiveness of CAP against both terbinafine-resistant and -sensitive isolates of the T. mentagrophytes complex.

Materials and Methods: Fifty clinical isolates and one reference susceptible strain (PFCC 5809) were studied. Terbinafine susceptibility was determined using the CLSI M38-A3 broth microdilution method, defining resistance as minimum inhibitory concentrations greater than 0.25 µg/mL. The resistant and susceptible isolates were subjected to CAP for 180 and 210 seconds. Growth inhibition was evaluated using mycelial dry weight in Sabouraud maltose broth and colony-forming unit (CFU) on Sabouraud dextrose agar. All studies were conducted in duplicate, with statistical significance set at p < 0.05.

Results and Discussion: Exposure to CAP decreased the growth of fungi in both resistant and susceptible isolates; however, the resistant strains showed greater inhibition. The most significant reduction was observed after 210 seconds of treatment, supported by dry weight and CFU analysis.

Conclusion: CAP exhibited potent inhibitory action against the terbinafine-resistant strains of T. mentagrophytes. In the light of increasing antifungal resistance and clinical burden caused by dermatophytosis, CAP may offer a promising alternative or adjuvant therapy. Further studies are required to optimize treatment parameters and evaluate clinical applicability.

Keywords
Cold atmospheric plasma
Fungal growth inhibition
Plasma-based antifungal therapy
Terbinafine-resistant dermatophytes
Trichophyton mentagrophytes complex