Indian Journal of Microbiology Research


Comparative evaluation of two direct microscopic methods in rapid diagnosis of superficial fungal infection


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Author Details: Rashmi P. Mahale, Raghavendra Rao M, Sowmya GS, Harsha Vardhan, Madhuri Kulkarni

Volume : 4

Issue : 2

Online ISSN : 2394-5478

Print ISSN : 2394-546X

Article First Page : 227

Article End Page : 230


Abstract

Introduction: Dermatomycosis is a common fungal infection seen in tropical and subtropical countries. Laboratory diagnosis of Dermatomycosis like dermatophytosis and Pityriasis versicolor depends on the demonstration of the etiological agents by microscopy and isolation of the fungi by culture. Culture on SDA is considered as gold standard however it is time consuming, so microscopic methods are used as rapid diagnostic tool.
Aims: Study was aimed at comparing two microscopic methods, KOH and Calcofluor white in the diagnosis of superficial fungal infections.
Methodology: Hair, nail and skin scrapings from patients who were clinically suspected with superficial fungal infections were divided into three parts and subjected to two direct microscopic methods (KOH and Calcofluor white) and culture.
Results: A total of 100 patients with superficial fungal infections were studied. 72 of them were clinically suspected cases of dermatophytosis and 28 of them were suspected cases of Pityriasis versicolor. Out of 100 samples, maximum number of samples were skin samples (84%) followed by nail (10%) and Hair (6%). Among the skin samples T.corporis (31%) was the predominant clinical manifestation followed by T.versicolor (28%). 28 cases of Tinea versicolor were not cultured. Out of 72 samples which were cultured, 29(40.27%) were culture positive and 43(59.7%) were culture negative, 32 were KOH positive whereas 39 samples were positive by CFW. Among culture positive samples T. rubrum was predominant isolate grown. Out of 100 samples 49 samples were KOH positive and 58 samples were Calcofluor white positive.
Conclusion: KOH wet mount using bright field microscopy is quick, inexpensive and routinely used for diagnosing fungal infections, but it does not produce a colour contrast and requires skill to interpret. While CFW provides a colour contrast and the diagnosis is easier, faster as present study also shows 10% of samples were CFW positive were missed by KOH examination.

Keywords:
Calcofluor white, Dermatophytosis, Potassium hydroxide, Superficial mycosis