DETECTION OF PARASITES WITH DNA-BINDING BISBENZIMIDE H33258 IN PNEUMOCYSTIS-CARINII AND LEISHMANIA CONTAINING MATERIALS

Even for routine purposes, standard staining of Pneumocystis- or Leish mania-containing materials, e.g., with Giemsa or Diff-Quik, is often u nsatisfactory due to poor contrast and to staining of irrelevant struc tures. In comparison, the bisbenzimide dye Hoechst 33258, a DNA-bindin g fluorochrome, allows a more precise analysis of such materials. Bisb enzimide stained all stages of these fungal or protozoal organisms wit h brilliant contrast against a uniformly dark background. The level of background luminescence and staining of detritus or non-DNA structure s was very low. Organisms were stained both outside of and within phag ocytic cells with equal intensity. Counting of individual microorganis ms, e.g., in macrophages heavily parasitized with Leishmania or in Pne umocystis-infected bronchoalveolar lavage, was simplified and more pre cise. Air-dried cell suspensions, cytocentrifuge preparations, impress ion smears, or cryocut micrographs showed the advantages of bisbenzimi de staining over Diff-Quik. Staining with bisbenzimide could be a valu able auxiliary technique for the analysis of material infected with a variety of microorganisms.