Microbiology of systemic fungal infections

The increased incidence of systemic fungal infections in the past two decades has been overwhelming. Earlier, it was pathogenic dimorphic fungi, which were known to cause systemic infections. However, starting from the 1960s, opportunistic fungi started causing more number of infections, especially in the immunocompromised host. More recently, newer and less common fungal agents are being increasingly associated with infection in immunosuppressed hosts. Amongst dimorphic fungi, infections due to Histoplasma capsulatum and Penicillium marneffei are increasingly reported in patients with AIDS in India. H. capsulatum is found country wide, but P marneffei remains restricted to Manipur state. Although both varieties of C. neoformans, C. neoformans var. neoformans (serotypes A & D), and C. neoformans var. gattii (serotypes B & C) are reported in India, most of the cases reported are of serotype A. Increased incidence of cryptococcosis is reported from all centers with the emergence of AIDS. Systemic infection due to species under Candida, Aspergillus and zygomycetes is widely prevalent in nosocomial setting, and outbreaks due to unusual fungi are reported occasionally from tertiary care centers. This global change in systemic fungal infections has emphasized the need to develop good diagnostic mycology laboratories in this country and to recognize this increasingly large group of potential fungal pathogens.