Development of indirect ELISA and its evaluation in comparison with KOH hydrolysis and fungal culture for the immuno diagnosis of Trichophyton rubrum and Trichophyton mentagrophytes infection in humans

Abstract

Trichophyton is a keratinophilic fungus that can invade keratinized tissues of humans and cause superficial mycoses called dermatophytosis. The objective of this study was to develop and evaluate indirect ELISA in comparison with gold standard methods such as direct microscopic examination of KOH mounts and fungal culture for the diagnosis of Trichophyton infection in humans. The present investigation reports the production and partial purification of T. rubrum mycelial antigens and production of specific polyclonal antibodies. It also reports the development and optimization of indirect ELISA and evaluation of its potential in comparison with gold standard methods for the diagnosis of Trichophyton infection in humans. The diagnostic sensitivity and specificity of Trichophyton indirect ELISA was 93.75% and 93.33% respectively. The positive and negative predictive values were high as well, found to be 93.75% and 90.00% respectively indicating usefulness of the assay. In all comparisons, the correlation coefficient (r) value was >0.5 indicating strong correlation between KOH hydrolysis test, fungal culture method and indirect ELISA. A significant correlation coefficient of 0.856 (P < 0.0001) was obtained between indirect ELISA and fungal culture method. This shows a good agreement between fungal culture method and indirect ELISA. The present study clearly shows diagnostic performance of Trichophyton indirect ELISA developed in this study is efficient as fungal culture method for the diagnosis of Trichophyton infection in humans.