New Contrast Stain for the Rapid Diagnosis of Dermatophytic and Candidal Dermatomycoses

Abstract

R apid diagnosis of superficial dermatomycoses is important so that treatment can be initiated without delay. We compared a new contrast stain with the routine test of potassium hydroxide (KOH) wet mount and culture for the diagnosis of dermatophytic and candidal dermatomycoses.Methods. Skin scrapings were taken from outpatients with superficial dermatomycoses and cultured in Sabouraud dextrose agar with cycloheximide. They were then evaluated under a microscope using both the KOH wet mount technique and the new contrast stain. Two investigators read the slides together but were blinded to all other test results.The new contrast stain contains 1% Chicago sky blue 6B and 8% KOH as the clearing agent. Staining was performed as previously described. 1 Slides were scanned at original magnification ϫ10 to locate blue-staining fungal hyphae. Dermatophytes were confirmed at original magnification ϫ40 on the finding of septate filaments. Candidal yeasts were detected as refractile oval budding yeast cells and/or pseudohyphae after lowering the condenser. Candidal slides were returned to the humidifying chamber and read again the following day to detect any change in staining intensity.A 20% KOH solution was used for the KOH wet mount, and microscopic examination was performed in the usual manner.

Comparative study of efficacy, rapidity of detection, and cost‐effectiveness of potassium hydroxide, calcofluor white, and Chicago sky blue stains in the diagnosis of dermatophytoses

“…The low specificity of both CW and CSB stains can be attributed to inability of the KOH test itself to detect true positives. Even in experienced hands, the false positive and false negative rates of KOH have been reported as 14% and 5–25%, respectively . However, when availability, ease of detection, and cost‐effectiveness were considered, CSB was found to be better than CW in the diagnosis of dermatophytoses.…”

“…However, they are technically demanding, require up to 48 hours to complete, and will not be available in laboratories in developing countries for the foreseeable future. In contrast to other studies (Table ), our study compared all the three methods at the end of 5 and 30 minutes and hence demonstrated that the CSB stain is a better stain for the rapid diagnosis of dermatophytoses because of ease of performance and differentiation of artifacts, rapidity of detection, better appreciation of morphology of fungal elements, and cost effectiveness.…”

“…Chicago sky blue (CSB) is tetrasodium 6,6′‐{(3,3′‐dimethoxy[1,1′‐bipheyl]‐4,4′‐diyl) bis(azo)} bis{4‐amino‐5‐hydroxynaphthalene‐1,3‐disulfonate}, which is also known as Atlantic resin fast blue . The CSB stain is a new contrast stain that has shown promising results as a rapid and reliable diagnostic method for dermatophytoses . It contains 1% CSB 6B and is used together with KOH as the clearing agent.…”

“…11,12 The CSB stain is a new contrast stain that has shown promising results as a rapid and reliable diagnostic method for dermatophytoses. 13,14 It contains 1% CSB 6B and is used together with KOH as the clearing agent. Cultures are more specific but have a higher percentage of false negatives.…”

A comparison of the contrast stains, Chicago blue, chlorazole black, and Parker ink, for the rapid diagnosis of skin and nail infections

“…Two other dyes available are Chicago blue 6,7 and chlorazole black. 4 The aim of this study is to compare Chicago blue-KOH and chlorazole black-KOH stains with the Parker ink-KOH stain and with culture, which in this study is considered the diagnostic gold standard.…”