Development of specific fluorescent-antibody test for tissue form of Penicillium marneffei

The diagnosis of penicilliosis marneffei can be difficult because the clinical manifestations mimic those of tuberculosis, histoplasmosis, and other mycotic infections. Furthermore, the tissue form of Penicillium marneffei can be confused with those of Histoplasma capsulatum and Cryptococcus neoformans. To facilitate the rapid detection and identification of P. marneffei in clinical materials, we sought to develop a specific indirect fluorescent-antibody (IFA) reagent for this dimorphic pathogen. Preliminary IFA studies with yeast-like cells (fission arthroconidia) of P. marneffei indicated that these cellular elements stained with antiglobulins against culture filtrate antigens and whole yeast-like cellular antigens. Both types of antiglobulins reacted with the yeast-like cells of P. marneffei and with H. capsulatum, but not with their respective mycelial forms. The antiglobulins also failed to react with the yeast and hyphal forms of a variety of other heterologous fungi. Specific antiglobulins useful in an IFA test for identifying P. marneffei yeast-like cells in culture or in clinical materials were produced by adsorptions with yeast-form cells of H. capsulatum. The yeast-like culture filtrate antigens of P. marneffei are preferred for use in the production of the specific antiglobulins because they stained P. marneffei yeast-like elements more intensely than antiglobulins produced against intact yeast-like cells.