Mycological study of tinea versicolor
Department of Skin and Microbiology, J.J.M. Medical College, Davangere - 577 004
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Sankara Rao I V, Rajashekhar N, Lava R. Mycological study of tinea versicolor. Indian J Dermatol Venereol Leprol 1997;63:168-169
AbstractMycological study of 100 cases of tinea versicolor was undertaken. Skin scrapings from 100 cases were subjected for culture in Sabouraud's dextrose agar, out of which 60 positive cultures (60%) were obtained.
Tinea versicolor (TV) is a common superficial fungal disease caused by a yeast-like organism, Pityrosporum orbiculare (Malassezia furfur). The organism is lipophilic and requires lipid in the medium to be grown in vitro. [1,2] Successful culture of this organism grows well at 37°C on Sabouraud′s agar containing streptomycin, penicillin and cycloheximide (actidione) and covered with a layer of sterile olive oil6
A survery of the literature reveals that only a few published reports of culture of this fungus are available. The purpose of this paper is to report the results of our attempts to culture this organism.
Materials and Methods
The study was conducted on 100 clinically diagnosed cases of TV attending Skin, STD and Leprosy OPD of J.J.M. Medical College, Davangere during the period of September ′94 to April ′96. Mycological study conducted on each case included: (1) Direct KOH preparation of specimen obtained by scraping for demonstration of fungal elements. (2) Culture of specimen on Sabouraud′s agar with chloramphenicol and cycloheximide. The material was inoculated at 2 to 3 sites into the media and layer of sterile olive oil was poured over the medium. The tubes were incubated at room temp (37°C). The cultures were examined daily for a period of 4 to 6 days before discarding as negative. The isolated fungi were identified by their colony characters and microscopic morphology. In all the positive cultures a smear was made and was stained with Gram′s stain. This Gram′s stained smear was examined under the oil immersion lens (100x).
The direct KOH examination of the skin scrapings revealed fungal elements in all the 100 cases studied, the culture gave positive growths only in 60 cases i.e., 60%. The culture in the remaining 40 cases did not reveal growth of these fungi. Pityrosporum colonies appeared in 4 to 6 days. The colonies were creamy-yellow in colour, 4 to 6mm in diameter and microscopic examination revealed many oval budding yeast cells. No hyphal elements were seen.
The present study was undertaken mainly to confirm the diagnosis of TV by mycological examination i.e., both direct microscopic examination of the fungal scrapings and culture. Though the demonstration of fungi was possible in all the 100 patients by direct microscopic examination, the culture gave positive growth only in 60% of cases. Though it has been mentioned by Martin et al (1993)6 that the cultures can easily be made from infected scales, we found it somewhat difficult to get positive cultures in all the cases. The culture negativity in majority of the cases indicates that more cautious precautions are necessary during the procedure of collection of the skin scraping material, while incubating the material into the media and also during the period of growth. The present study is only an attempt to establish culture for the growth of pityrosporum and it is not a final work and the work has to be further continued to establish culture technique in perfect manner.
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