Immunomycology: rapid and specific immunocytochemical identification of fungi in formalin-fixed, paraffin-embedded material.

We report the rapid (less than 1 hr), immunocytochemical identification of various fungi in formalin-fixed, paraffin-embedded tissues using antisera originally developed for use in immunodiffusion assays. Primary antisera directed towards fungal genera including Aspergillus, Blastomyces, Candida, Coccidioides, Cryptococcus, Histoplasma, and Sporothrix were examined. The specificity of each antiserum was evaluated by the presence or absence of crossreactivity with other morphologically similar fungi in both paraffin-embedded pure fungal cultures and tissues with culture-confirmed fungal infections. Each antiserum reacted strongly with the fungus to which it had been raised, whether examined in pure culture or infected tissues. The antisera raised against Candida, Cryptococcus, and Sporothrix did not exhibit cross-reactivity with any other fungus tested. However, the antisera raised to Aspergillus, Blastomyces, Coccidioides, and Histoplasma demonstrated significant crossreactivity with other genera of fungi, thus precluding their routine use in diagnostic immunocytochemistry. The results indicate that immunocytochemistry may provide an important adjunct to other methods, such as immunodiffusion or complement fixation assays and histochemical stains such as the Grocott methenamine silver or periodic acid-Schiff, when attempts are made to specifically identify certain fungi in formalin-fixed, paraffin-embedded tissues before mycology culture results are available.

Dual organism infection in biopsy specimens from immunocompromised patients: two cases demonstrated by immunocytochemistry.

We report two cases in which immunocytochemistry demonstrated simultaneous infections within a single biopsy specimen obtained from each of two immunocompromised patients in whom multiple organism infection was not suspected. Using a rapid immunocytochemical technique, Pneumocystis carinii and Cryptococcus neoformans were demonstrated in a transbronchial lung biopsy from the first patient; Candida and cytomegalovirus were demonstrated in an endoscopic biopsy of the esophagus from the second patient. Routine hematoxylin and eosin as well as special stains failed to establish the presence of more than one infectious agent in either case. Mycology cultures ultimately confirmed the presence of Cryptococcus in the first case, but cultures were not performed in the second case due to the scant amount of tissue obtained from the biopsy. The results indicate that concurrent infection by more than one opportunistic organism in immunocompromised patients can easily remain unrecognized. The use of immunocytochemistry may thus provide an important adjunct to routine and special stains or specific cultures.