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In this report, we demonstrate that tinea versicolor retains topical gentian violet. We did not observe this phenomenon in other hypopigmenting disorders, and thus this observation could be used as a simple bedside test. We call this phenomenon in vivo Gram staining.
Gentian violet is a commonly used topical anti-infective that has efficacy against gram-positive bacteria and fungi. Given that gentian violet has a long track record in human skin disease, we routinely use it in the treatment of gram-positive cutaneous infections and fungal infections.1,2 We present a case of a patient who has been previously diagnosed with tinea versicolor and treated with topical therapy who noted persistence of lesions (Figure, A). We applied gentian violet to his skin and noted a dramatic accentuation of infected areas compared with unaffected skin (Figure, B). Confirmation of infection was made with potassium hydroxide preparation (Figure, C). We have named this phenomenon in vivo Gram staining.
A, The patient had a history of tinea versicolor but was uncertain if he had been successfully treated. B, To determine whether he still was colonized with tinea versicolor, topical gentian violet (crystal violet) was applied to his back; note the accentuation of infected patches by gentian violet. C, Confirmation of infection was noted by positive potassium hydroxide preparation, revealing classic “spaghetti and meatball” conformation of fungus (original magnification ×100).
Gram stain is used to categorized bacteria into gram-positive and gram-negative organisms. The basic mechanism of Gram staining is the retention of crystal violet, which is another name for gentian violet. Gram-positive bacteria and fungi retain gentian violet in the presence of an alcohol wash, while gram-negative bacteria do not retain gentian violet because the compound does not penetrate the cell wall of gram-negative bacteria. The retention of gentian violet is likely due to the formation of an adduct, which is resistant to decolorization. Recently, our research group3 demonstrated that gentian violet forms a covalent adduct with thioredoxin reductase 2, a highly conserved protein from bacteria to humans, and is likely a candidate for the retention of gentian violet by the fungus. An additional explanation for selective dye retention is alterations in either host or fungal lipids. Unaffected skin does stain with gentian violet, but the affected areas stain more intensely.
This observation can serve as a potential bedside diagnostic test because other conditions, such as pityriasis rosea, atopic dermatitis, and vitiligo do not retain gentian violet. Thus, in vivo Gram staining has potential to be a rapid diagnostic test, especially given the prevalence of tinea versicolor in the developing world, as well as a potential therapeutic agent. Further studies of the antifungal activity of gentian violet are indicated.
Corresponding Author: Dr Arbiser, Department of Dermatology, Emory University School of Medicine, WMB 5309, 1639 Pierce Dr, Atlanta, GA 30322 (firstname.lastname@example.org).
Published Online: May 15, 2013. doi: 10.1001/jamadermatol.2013.2699
Conflict of Interest Disclosures: None reported.
Funding/Support: Dr Arbiser was supported by Emory Skin Disease Research Core Center grants RO1 AR47901 and P30 AR42687 from the National Institutes of Health, as well as funds from the Rabinowitch-Davis Foundation for Melanoma Research and the Betty Minsk Foundation for Melanoma Research.
Spence-Shishido A, Carr C, Bonner MY, Arbiser JL. In Vivo Gram Staining of Tinea Versicolor. JAMA Dermatol. 2013;149(8):991-992. doi:10.1001/jamadermatol.2013.2699