Comparison of processing techniques for detection of Pneumocystis carinii cysts in open-lung biopsy specimens

Abstract

Methenamine silver stain was used to compare the number of cysts of Pneumocystis carinii contained in lung concentrate smears of homogenized lung tissue with the number in impression smears. Results were also compared with histopathological examination of methenamine silver-stained paraffin-embedded sections. Of slides from 23 preparations, a greater number of cysts were contained in concentrate smears than in impressions (P < 0.001). In four preparations, cysts were noted in concentrate smears only. All concentrate smears were positive, whereas 11 of the 23 histopathological sections were negative (P < 0.01). The ability to detect the cyst phase of P. carinii in lung tissue is enhanced by the use of concentrate smears.

Techniques for examining Pneumocystis carinii in fresh specimens

“…Clinical and investigative interest in P. carinii has long focused on the morphological and staining properties of the organism. The most common type of study has involved staining of lung imprint smears or tissue sections to improve the rapidity of diagnosis (10,19,21,28). Stains (e.g., methenamine silver, toluidine blue 0, cresyl echt violet, and Gram Weigert) which selectively stain the wall of the cyst have been popular because they provide easy identification of this form of the organism (3,4,29).…”

The Microscopic Identification of Pneumocystis carinii

“…1.5 cm in dim. on a glass slide [2]. The slides were then stained with toluidine blue 0 [4], methenamine-silver nitrate [8], Fontana; Giemsa; methylene blue Loeffler or Gram modified [l].…”