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

Faeces of immunocompromised patients are often contaminated with the chitin -containing spores of microsporidia and Candida, which exclude the use of t he chitin-specific fluorescent brightener Calcofluor white M2R for the iden tification 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 ty pes of spores. As a basis for diagnosis, a difference in the fluorescence p attern (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 identif ied, while Candida spores show a reddish purple colour. Under the light mic roscope microsporidian spores show a light red colour with nonstained vacuo le spots or strips in contrast to the yeast spores with their red-brown col our. This combination technique offers a highly specific means for the diag nosis of microsporidia spores in faeces.