Detection of Pneumocystic carinii in immuno-suppressed rats by different histological stains and immunological assays.

Detection of P. carinii in lung sections of 35 immuno-suppressed albino rats was evaluated using five histological stains (toluidine blue "O", Giemsa, Gram's stain, PAS and H & E) and two immunological assays (indirect immunofluorescence [IIF],, and indirect immunoperoxidase [IIP]) using polyclonal antibody, raised in white New Zealand rabbits, against rat P. carinii. In spite of the high sensitivity of the histological stains, they yield hazy details insufficient for easy identification with difficult interpretation. However, Gram and PAS stains provided a better visualization with easy identification of the parasite. On the other hand, both immunological assays allowed an accurate rapid interpretation of the stained slides. The IIP technique, having 100% sensitivity in detecting the precipitated parasite antigens with absolute specificity, seems to be a good diagnostic tool for detecting P. carinii in lung sections.