Specific Identification and Antifungal Susceptibility Pattern of Clinically Important Dermatophyte Species Isolated from Patients with Dermatophytosis in Tehran, Iran

With regard to the increasing number of antifungal-resistant dermatophytes, the requirement for precise identification of causative agents of infections and antifungal susceptibility test is vital. Antifungal susceptibility testing of dermatophytes plays a pivotal role in managing dermatophytosis. The current study aimed at determining antifungal susceptibility profile of 161 important dermatophyte species isolated from Iranian patients.
The current descriptive, cross sectional study was conducted on 508 clinically suspected samples of dermatophytosis collected and identified by conventional methods. All dermatophyte isolates were identified using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The susceptibility of dermatophyte strains to two routine antidermatophyte agents (terbinafine and griseofulvin) was evaluated using micro-dilution method according to CLSI (the clinical and laboratory standards institute) M38-A2 guidelines. Trichophyton rubrum PTCC 5143 and Candida krusei ATCC 6258 were used as quality controls.
Among 161 dermatophyte isolates, T. interdigitale was reported as the most frequent species isolated from patients using PCR-RFLP and Microsporum ferruginum was the least isolated species. The minimum inhibitory concentration (MIC) values of griseofulvin and terbinafine were ranged 0.0312 - 8 and 0.008 - 4 µg/mL, respectively. The most susceptible and resistant species to griseofulvin were T. interdigitale (MIC = 0.0312 µg/mL) and T. interdigitale/T. rubrum (MIC = 8 µg/mL), respectively. The results indicated that T. verrucosum (MIC = 0.008 µg/mL) was the most susceptible species to terbinafine, whereas T. interdigitale and T. rubrum were the most resistant species to it (MIC = 4 µg/mL).
The obtained results assist clinicians to monitor the trend and be able to choose effective medications to treat patients with dermatophytosis, especially in countries such as Iran, where dermatophytosis is still a public health problem.