Microsporidia and Candida spores: their discrimination by Calcofluor, trichrome‐blue and methylene‐blue combination staining

Abstract

Summary Faeces of immunocompromised patients are often contaminated with the chitin‐containing spores of microsporidia and Candida, which exclude the use of the chitin‐specific fluorescent brightener Calcofluor white M2R for the identification of microsporidian spores. We developed a combination staining of Calcofluor white M2R with modified trichrome‐blue staining and subsequent methylene‐blue incubation which permits discrimination between these two types of spores. As a basis for diagnosis, a difference in the fluorescence pattern (365–440 nm) is combined with a difference in the light microscopic staining pattern. Under fluorescence conditions microsporidia spores have a spotted, brilliant white Calcofluor fluorescence and can easily be identified, while Candida spores show a reddish purple colour. Under the light microscope microsporidian spores show a light red colour with nonstained vacuole spots or strips in contrast to the yeast spores with their red‐brown colour. This combination technique offers a highly specific means for the diagnosis of microsporidia spores in faeces.