2-hydroxystilbamidine isethionate: a new fluorochrome for use in general pathology. II. The selective demonstration of fungi.

Paraffin sections of kidney, lung and oesophagus containing Aspergillus sp., Cryptococcus neoformans and Candida sp. were taken from human post mortem material and from the marmoset Callithrix jacchus. Sections were stained for 1-5 min in buffered 2-hydroxystilbamidine isethionate containing sodium metabisulphite after pre-oxidation in 1 per cent aqueous periodic acid. Sections were dehydrated, cleared and mounted in Polymount. When excited with UV light hyphae and fungal bodies fluoresced white contrasting sharply with yellow nuclear fluorescence. With blue light nuclei and fungi fluoresced yellow. Staining with the fluorochrome was pH dependent and behaved as a Schiff type reagent indicative of its probable behaviour as a basic dye. The method was simple, rapid and provided permanent fluorescent preparations which over a number of years did not fade with routine storage.