Diagnosis of dermatophytoses: Comparison of mycological techniques

Abstract

Background: Dermatophytes are a group of closely related fungi that have the capacity to invade keratinized tissue (skin, hair, and nails) of humans and other animals to produce an infection. Infection by this fungi are restricted to the non-living cornified layers as they lack the ability to penetrate the deeper tissues of immuno competent hosts. The great variation in clinical presentation is related to the involved species of fungus, size of the inoculum, involved site and immune status of the host. There are three genera of dermatophyte fungi: Trichophyton, Microsporum and Epidermophyton based on microscopic features. Each genus is characterized by a specific pattern of growth in culture and by the production of macroconidia or microconidia. The Trichophyton species usually infect the skin, hair and nails. Microsporum species infect the skin and hair but not the nails. Epidermophyton species infect the skin as well as nails but not hair. This study was carried out to determine the etiological agents in different forms of dermatophytosis and to compare the various laboratory techniques in the diagnosis of dermatophytosis. Materials and method: The study was conducted at the department of Microbiology, Srinivas Institute of Medical Sciences and Research Centre, Mangalore, India. 270 specimens obtained from clinically suspected cases of dermatophytoses between December 2017 to December 2019 were included in the study. The samples included skin scraping, nail clipping and plucked hair. The specimen was then subjected to Microscopic examinations like KOH, PAS, and Calcofluor white stain and Culture on SDA, SDA with Chloramphenicol and DTM. Results: Male patients infected were found to be 48.88% and female patients were 51.11%. The most common affected age group was 21-30 years (25.1%). More than 92.59% of samples were from Tinea unguium. Fungi was demonstrated in 31.85% of cases, by KOH wet mount, 41.48% by calcofluor white stain and 49.62% by PAS. Out of 135 specimens, 48 specimen yielded growth giving 35.55% culture positivity on SDA with chloramphenicol. Conclusion: A success rate of 41.48% was achieved for detecting fungal elements by microscopy as compared to culture. PAS Stain shows high reliability and sensitivity for detecting onychomycosis compared to KOH and mycological culture. PAS and the culture combination is superior to combined KOH and culture for detection of dermatophyte infection. Ninety six isolates were obtained from 270 patients which shows the prevalence of the isolate in and around Mangalore

Dermatophytosis and its risk factors among children visiting dermatology clinic in Hawassa Sidama, Ethiopia

“…Microbiological laboratory analysis was based on the study Nagar, S.N., Diagnosis of dermatophytosis 14 . Each sample was treated with 1–2 drops of 10% KOH solution for 15–30 min and microscopically examined for the presence of fungal elements (spore and hyphae) under a light microscope at 10 × and 40 × magnification power.…”