What Kind of Fungi Are Pneumocystis?
Members of the genus Pneumocystis are microscopic yeast-like fungi that reside in the lungs of almost every mammal that has been evaluated for their presence. They grow extracellularly in the alveoli of mammals and are considered to be host obligate, as they cannot grow outside the lung on artificial media. Pneumocystis species (spp.) are typically restricted to the lungs, although extra-pulmonary manifestations have been reported [1]. Considered to be zoonotic (able to infect more than one mammalian species), these organisms once were referred to as a single genus and species, “Pneumocystis carinii”. It is now clear that distinct species of Pneumocystis infect different mammalian hosts. Each mammalian species has at least one species of Pneumocystis that it harbors which cannot infect another mammalian species (species specificity). Pneumocystis spp. have suffered many identity crises, beginning with their initial identification in 1909, when they were thought to be part of the life c
