Clinico-mycological Study of Otomycosis Comparing the Cavity Slide Technique and the Conventional Agar Block Slide Culture

Abstract

Introduction: Otomycosis is a sub-acute or chronic superficial fungal infection of the external auditory canal that occurs primarily in hot dry weather of tropics and sub tropics. The disease occurs in all age groups and is generally unilateral in presentation. Different species of Aspergillus and Candida usually invade the ear canal following a primary bacterial infection although other fungal pathogens are also infrequently associated with otomycosis. Slide culture technique is often used to delineate the fungal etiology in otomycosis however the morphology is not very clear as compared to the cavity slide culture which preserves the morphology well. Aim: To isolate various fungal agents involved in otomycosis and to compare the cavity slide culture technique with the conventional agar block slide culture for their identification. Materials and Methods: A total of 120 cases were studied from January 2015 to June 2016. Ear discharge specimen were collected on three sterile cotton swabs. Direct examination of the specimen was carried out by Gram stain and 10% KOH mount. All specimens were inoculated on Sabouraud dextrose agar, Blood agar and Mac Conkey agar and only the ones with fungal growth were further processed. Comparison of agar block slide culture and cavity slide culture technique was done for identification of fungi. Statistical analysis was done using one-way ANOVA (analysis of variance) method and a p-value of <0.05 was taken as significant. Results: Out of 120 fungal isolates the most common fungal isolate was Aspergillus flavus (39.2%) followed by A. niger (26.7%), A. fumigatus (15%), Penicillium (10.8%), Candida glabrata (5%) and Candida albicans (4%). Prevalence in females (65.8%) was more than males and itching (67.5%) was the most common presenting symptom. The cavity slide culture technique was found to be better in terms of proper visualisation and preservation of morphology of fungi. Growth was appreciated within 72 hours, with minimal morphological distortion of conidial attachment especially for Aspergillus and Penicillium spp. Less quantity of media was used in cavity slides which were stored for a week without the chances of contamination. Conclusion: Cavity slide culture should be used routinely for the visualisation and identification and fungi as the morphology is better preserved and appreciated in it and the results are available in a short period of time.

Keywords

• ear canal
• fungal infection
• morphological identification