Evaluation of the Use of Bioactive Dye for Rapid Anti-dermatophytes Susceptibility Testing‎ ‎

Background and study aim: Fungal infections affecting the epidermis, hair, and nails are mostly caused by dermatophytes. They can infect immunocompromised and immune-competent patients as well. The study aims to evaluate the use of Resazurin in anti-dermatophytes susceptibility testing. Patients and Methods: Patients with dermatophytic infection, attending dermatology outpatient clinic in Ain Shams University Hospital were examined and 50 clinical specimens were collected. All clinical specimens were cultured on Sabarouds dextrose agar (SDA). To improve sporulation, isolates from SDA were subcultured on Potato Dextrose Agar (PDA) and incubated at 28°C for 7 days. The colonies were collected in sterile saline, to adjust fungal suspension to 0.5 McFarland. The antifungal susceptibility was made using two methods: disc diffusion (DD) and broth microdilution (BMD) with and without Resazurin. Results: Antifungal susceptibility results were available after 24 hours by broth microdilution with bioactive dye (Resazurin). While antifungal susceptibility by broth microdilution method without bioactive dye results was available after 48-72 hours and disc diffusion results were available after an incubation period of 7 to 15 days. In addition, using bioactive dye (Resazurin) method was easier in visual interpretation. There were a perfect agreements between the antifungal susceptibility testing of Itraconazole (kappa 1.00), Terbinafine (kappa 0.947) and Fluconazole (kappa 0.878) by disk diffusion method and Broth micro-dilution method without and with bioactive dye (Resazurin). Conclusion: Usage of bioactive dyes such as Resazurin can help in providing rapid and accurate antifungal susceptibility results for better patient care.