[Continuous axenic cultivation of Pneumocystis carinii isolated from the bronchoalveolar lavage fluid of infected rat].

OBJECTIVE: To establish axenic cultivation of Pneumocystis carinii (P.c). METHODS: The organisms of P.c were isolated from the bronchoalveolar lavage fluid (BALF) of the rats with Pneumocystis carinii pneumonia (PCP) and cultured in a medium which was based on IMDM(GIBCO) supplemented with S-adenosyl-L-methionine, putrescine, N-acetyl glucosamine, putrescine, L-cysteine and L-glutamine, and newborn calf serum. The organisms cultured in the system were identified by observing the morphology of cysts in smears stained with Gomori's methenamine silver nitrate stain (GMS). Ultrastructure of the cysts/trophozoites was examined by transmission electron microscopy. The sequences of mitochondrial large ribosomal DNA subunit of the cultured organisms were compared with the Pneumocystis carinii f.sp. ratti variant isolate (GenBank No U20173) and Pneumocystis carinii f.sp.hominis (GenBank No M58605). RESULTS: Five isolates of P. carinii received from BALF of 8 rats with PCP were cultured axenically and continuously in the system. The cultured organisms could be stored in frozen condition and used to reinitiate culture, and were amplified by 19-22 times within 72 h. The morphology, ultrastructure and gene sequencing of the cultured organisms confirmed that the isolated organisms were P. carinii. CONCLUSION: Five continuously and axenicly cultured isolates of P. carinii have been received.

Pneumocystis melanins confer enhanced organism viability.

Pneumocystis continues to represent an important opportunistic fungal pathogen of those with compromised immunity. Thus, it is crucial to identify factors that affect its viability and pathogenicity. We previously reported the first identification of melanins in Pneumocystis. In the present study, we sought to further characterize these components and define the function for these melanins. Melanins extracted from Pneumocystis and melanized Pneumocystis cells were analyzed by electron spin resonance spectroscopy, revealing spectra consistent with melanins from other fungi. Immunofluorescence assays using anti-melanin monoclonal antibodies showed that melanins are widely present across Pneumocystis host species, including mouse-, ferret-, and human-derived Pneumocystis organisms, as well as Pneumocystis carinii derived from rat. Using immunoelectron microscopy, melanins were found to localize to the cell wall and cytoplasm of P. carinii cysts, as well as to intracystic bodies within mature cysts. Next, the role of melanins on the maintenance of Pneumocystis viability was determined by using quantitative reverse transcription-PCR measurement of the heat shock protein mRNA under adverse environmental conditions. Using a new method to promote the melanization of Pneumocystis, we observed that strongly melanized Pneumocystis retained viability to a greater degree when exposed to UV irradiation or desiccation compared to less-pigmented organisms. These studies support our previous identification of Pneumocystis melanins across the genus, further characterize these Pneumocystis components, and demonstrate that melanins protect Pneumocystis from environmental stressors.

[Observation on the ultrastructure of Pneumocystis carinii].

OBJECTIVE: To study the life cycle and morphology of Pneumocystis carinii by ultrastructural observation. METHODS: Wistar rat model of P. carinii infection was established by subcutaneous injection with dexamethasone. Lung tissue of the infected rats was used for the transmission electron microscopical study. RESULTS: The organisms were mainly present in the lung alveolar cavity, and also in the alveolar septum, pulmonary macrophages and neutrophils. More trophozoites of P. carinii attached to the type I alveolar epithelial cells, and rarely to the type II alveolar epithelial cells. Most of these trophozoites showed pseudopodial evaginations on their pellicles. The nucleus-associated organelle and spindle microtubules were observed in some trophozoites. The precyst phase was in three forms: early, intermediate and late form. Synaptonemal complexes indicating meiotic nuclear divisions and a clump of mitochondria were also observed in the precyst. The pellicle of the cyst has a thickened portion with a pore. There were nucleus with nucleolus, mitochondrion, vesicles, endoplasmic reticulum and numerous ribosomes in the organisms, and tubular expansions on its surface. CONCLUSION: The life cycle of P. carinii consists of trophozoite, precyst and cyst stages. The presence of a single pore in the cyst wall reveals that pore formation may be a mode of excystation for intracystic bodies of P. carinii.

Basic biology of Pneumocystis carinii: a mini review

Basic aspects of cell biology of Pneumocystis carinii are reviewed with major emphasis on its life cycle and the structural organization of the trophozoites and cyst forms. Initially considered as a protozoan it is now established that Pneumocystis belongs to the Fungi Kingdom. Its life cycle includes two basic forms: (a) trophozoites, which are haploid cells that divide by binary fission and may conjugate with each other forming an early procyst and (b) cysts where division takes place through a meiotic process with the formation of eight nuclei followed by cytoplasmic delimitation and formation of intracystic bodies which are subsequently released and transformed into trophozoites. Basic aspects of the structure of the two developmental stages of P. carinii are reviewed.

Basic biology of Pneumocystis carinii: a mini review.

Basic aspects of cell biology of Pneumocystis carinii are reviewed with major emphasis on its life cycle and the structural organization of the trophozoites and cyst forms. Initially considered as a protozoan it is now established that Pneumocystis belongs to the Fungi Kingdom. Its life cycle includes two basic forms: (a) trophozoites, which are haploid cells that divide by binary fission and may conjugate with each other forming an early procyst and (b) cysts where division takes place through a meiotic process with the formation of eight nuclei followed by cytoplasmic delimitation and formation of intracystic bodies which are subsequently released and transformed into trophozoites. Basic aspects of the structure of the two developmental stages of P. carinii are reviewed.

Iron chelator daphnetin against Pneumocystis carinii in vitro.

BACKGROUND: Although there are several drugs and drug combinations for the treatment of Pneumocystis carinii (P. carinii) pneumonia, all drugs have the toxicity as well as low efficacy. Iron chelators have been proposed as a source of new drugs for combating these infections. We hypothesized that iron chelators would suppress the growth of P. carinii by deprivation of the nutritional iron required for growth. In this study, a short-term axenic culture system of P. carinii was established. Daphnetin (7,8-dihydroxycoumarin), a known iron chelator, was demonstrated to exhibit in vitro activity against P. carinii in this system. METHODS: P. carinii organisms were obtained from the lungs of immunosuppressed rats. The culture system consisted of Iscove Dulbecco Eagle's Minimum Essential Medium (IMDM), supplemented with S-adenosyl-L-methionine, N-acetylglucosamine, putrescine, L-cysteine, L-glutamine, 2-mercaptoethanol, and fetal bovine serum, and was maintained at 37 degrees C, in 5% CO(2), 95% O(2), at the optimal pH of 8.0. The culture system was used to assess the effect of daphnetin on the proliferation of P. carinii organisms. The ultrastructures of the treated organisms were observed by transmission electron microscopy. RESULTS: The number of cysts and trophozoites increased 8- to 9-fold and 11- to 12-fold, respectively, after 10 days of culture. Daphnetin was found to suppress the growth of P. carinii in a dose-dependent manner at concentrations between 1 micromol/L and 20 micromol/L. The inhibitory activity was suppressed by the chelation of daphnetin with ferrous sulfate in a 2:1 molar ratio, but it was not suppressed by mixing the culture medium with magnesium sulfate. Reduction of P. carinii numbers after treatment with daphnetin correlated with morphological changes in the organisms, as determined by transmission electron microscopy. CONCLUSIONS: Daphnetin can suppress the growth of P. carinii in vitro. The efficacy of daphnetin in suppressing the the growth of P. carinii in vitro is related to its ability to chelate iron.

Pneumocystis carinii: an update.

Pneumocystis produces respiratory infection in immunocompromised individuals of several species of mammals, including humans. Each mammalian species has its own specific Pneumocystis species, which does not cross-infect other mammals. The species infecting humans has now been renamed P. jerovici, since P. carinii is reserved for one of two species infecting rats. Long believed to be a protozoan, Pneumocystis is now classified as an Archiascomycetous fungus. This is based on new molecular taxonomic techniques using DNA sequence analysis of srRNA genes. Only two of about 140 copies of the gene that exist in Pneumocystis were used for sequencing, so the evidence is not conclusive; however, it is supported by morphological evidence such as fungus-specific nucleus-associated organelles for cell division. There is also ultrastructural evidence of meiotic division and sexual conjugation. Clinically, several lines of evidence suggest the improbability of latent infection. Adult infections appear to be new infections, a fact that invites a new perspective on prevention.