Staining of microsporidian spores by optical brighteners with remarks on the use of brighteners for the diagnosis of AIDS associated human microsporidioses.

Conditions for the effective fluorescence labelling of microsporidian spores by optical brighteners, based on the presence of chitin in the spore wall, are described. Spores of Vairimorpha ephestiae, V. necatrix, V. plodiae, Nosema bombycis, N. apis, N. algerae, Encephalitozoon cuniculi and Enterocytozoon bieneusi were examined. The degree of binding of Calcofluor White M2R (CFW) to untreated spores depends on the conditions and time of storage and the degree of bacterial contamination of the spore sample. Unpurified spores, stored in water are unreliable as control material for the estimation of CFW labelling. However, spores subjected to alkaline treatment by NaOH before CFW application are visualized with ease under all experimental conditions by their bright, not quenching fluorescence in shortwave light (approximately 350 nm) in CFW dilutions of 10(-4) or even lower. Similar improvement in labelling is achieved by exposing spores to CFW dissolved in 0.5-1N NaOH. As well as Calcofluor White M2R other optical brighteners (e.g. Uvitex 2B, Ciba-Geigy or Rylux BA, Ostacolor) can be used for labelling of spores.