Staining of Cysts of Pneumocystis jiroveci (P. carinii) With the Fluorescent Brighteners Calcofluor White and Uvitex 2B: A Review

The use of the fluorescent brighteners calcofluor white (CFW) and Uvitex 2B as cyst wall stains for the detection of Pneumocystis jiroveci (P. carinii) in respiratory tract specimens is reviewed. Most of the comparisons in the literature are with CFW and direct or indirect fluorescent antibody stains (immunostains), and most of these studies found the immunostains to be more sensitive than CFW, but less specific. Attractive features of CFW over immunostains are its simplicity and rapidity, its specificity (the characteristic, distinctive appearance of the stained cyst wall), and its low cost. If present in the specimen, other fungi may be stained and detected. The reported variations in the staining, or lack thereof, of P. jiroveci cysts with fluorescent brighteners are reviewed and the need for an awareness of these differences, and their implications in the quality control of stain procedures, is stressed.