Basic biology of Pneumocystis carinii: a mini review

Tropical dermatology: Tropical diseases caused by protozoa

“…In addition, homology between the ribosomal RNA and mitochondrial DNA of P jirovecii and fungi has been shown. 191 However, the sterol component of fungi membranes, ergosterol, has not been identified in P jirovecii. 188 Pneumocystis is a ubiquitous and nonvirulent parasite in healthy individuals, but causes opportunistic infections in hosts with depressed immune function.…”

The Pneumocystis life cycle

“…All known life cycle stages of Pneumocystis have been found in the lungs of infected mammals and, more rarely, in extrapulmonary locations primarily in severely immunocompromised hosts (Ng et al 1997, Anuradha & Sinha 2007. Several authors have drawn slightly different hypothetical life cycle schemes in which both sexual and asexual reproduction alternate in vivo (Yoshida et al 1984, Yoshida 1989, Cushion 2004, Dei-Cas et al 2004, De Souza & Benchimol 2005, Thomas & Limper 2007, Aliouat-Denis et al 2008. Lack of robust, long-term culture has prevented detailed dynamic follow-up of differentiation of the Pneumocystis life cycle stages.…”

“…As indicated above, in the infected lungs of patients or immunosuppressed laboratory animals, trophic forms represent 90-95% of the total parasite population. Mainly for this reason, it is currently thought that Pneumocystis proliferation results from active binary fission of trophic forms (Cushion 2004, De Souza & Benchimol 2005. Although few ultrastructural micrographs of binary fission have been reported (Richardson et al 1989), 15 years of studying Pneumocystis ultrastructure led us to hypothesise that nuclear division would only occur within the cystic forms (Aliouat et al 1999, Dei-Cas et al 2004).…”

Healthcare related transmission of Pneumocystis pneumonia: From key insights toward comprehensive prevention

“…P. jirovecii lives almost exclusively in the human alveoli. Morphological studies have revealed 3 distinct stages: the trophozoite (trophic form), the sporocyte, and the cyst . Primary infection, which is generally mild or asymptomatic, occurs early in life, after which a chronic or intermittent colonization state may persist .…”