Pneumocystis jirovecii (formerly P. carinii ) is a yeast-like mushroom of the genus Pneumocystis . The causal organism of pneumonia Pneumocystis , this is an important human pathogen, especially among immunocompromised hosts. Prior to its discovery as a special human pathogen, P. jirovecii was known as P. carinii .
Video Pneumocystis jirovecii
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The complete cycle of one of the species Pneumocystis is unknown, but may all resemble the other in the genus. The terminology follows the term zoology, not the mycological term, reflecting an early deterministic error as a protozoan parasite. This is an extracellular parasite. All stages are found in the lungs and since they can not be cultivated ex vivo , direct observation of life Pneumocystis is difficult. The trophozoite stage is considered to be equivalent to what is called a vegetative state of another species (such as Schizosaccharomyces pombe) which, like Pneumocystis, belongs to the Taphrinomycotina branch of the mushroom kingdom. The trophozoite stage is single-celled and appears amoeboid (multilobed) and is closely related to the host cell. The globular cyst finally formed which has a thicker wall. In a cyst like ascus, eight forms of spores are released through the rupture of the cyst wall. Cysts often collapse forming a crescent-shaped body visible in stained tissue. If meiosis occurs inside the cyst, or what the genetic status of different cell types is not known for sure.
Maps Pneumocystis jirovecii
Medical relevance
Pneumocystis pneumonia is an important immunocompromised human disease, especially patients with HIV, but also patients with a strongly suppressed immune system for other reasons, for example, after bone marrow transplantation. In humans with normal immune systems, it is a very common silent infection.
Identified by methenamine silver stains of lung tissue, type I pneumocytes, and type II pneumocytes over-replicate and damage the alveolar epithelium, causing death by asphyxia. The fluid leaks into the alveoli, producing an exudate that looks like the appearance of a honeycomb/cotton on the hematoxylin and eosin slides. The drug of choice is Trimethoprim/sulfamethoxazole, pentamidine, or dapsone. In HIV patients, most cases occur when the CD4 cell count is below 200 cells per microliter.
Nomenclature
Initially, the name Pneumocystis carinii was applied to organisms found in mice and humans, because the parasite was not yet known to be host-specific. In 1976, the name " Pneumocystis jiroveci " was proposed for the first time, to distinguish organisms found in humans from variants of Pneumocystis on other animals. The organism was so named in honor of the Czech parasitologist Otto Jirovec, who described pneumonia in human pneumonia in 1952. After DNA analysis showed significant differences in human variants, the proposal was re-established in 1999 and has come. for general use.
The name was spelled in accordance with the International Code of Zoological Nomenclature, because the organism was believed to be a protozoa. After it became clear that it was a mushroom, the name was changed to Pneumocystis jirovecii , according to the International Code of Nomenclature for algae, fungi, and plant (ICNafp), which required that names be spelled with my double ( ii ). These two spellings are commonly used, but according to ICNafp, P. jirovecii are correct. The changes in ICNafp now recognize the validity of the publication of 1976, make a redundant 1999 proposal, and cite Pneumocystis and P. jiroveci as examples of changes in ICN Article 45, Ex 7. Name < i> P. jiroveci is typed (both in-lectotypified and epitypified) by samples from human autopsies dating from the 1960s.
The term PCP, which is widely used by practitioners and patients, has been maintained for convenience, arguing that it now stands for P the more common c
The name P. carinii is not true for human variants, but still describes the species found in mice, and the name is characterized by isolates from mice.
Pneumocystis genome
Pneumocystis species can not grow in culture. Therefore, the availability of human disease-causing agents, P. jirovecii , is limited. Therefore, an entire genome investigation of Pneumocystis is largely based on true P. carinii available from experimental mice that can be maintained with infection. Genetic material of other species, such as P. jirovecii , can be compared with the P. carinii genome .
The genome of P. jirovecii has been sequenced from bronchoalveolar lavage samples. The genome is small, low in G C, and lacks the amino acid biosynthesis enzyme.
History
The earliest report of this genus appears to be about Carlos Chagas in 1909, who found it in experimental animals, but confused it with part of the life cycle of Trypanosoma cruzi (the agent responsible for Chagas disease) and then called the two organisms < i> Schizotrypanum cruzi , a trypanosome form infects humans. The rediscovery of the pneumocystis cyst was reported by Antonio Carini in 1910, also in Brazil. The genus was rediscovered in 1912 by DelanoÃÆ'Â «and DelanoÃÆ'«, this time at the Pasteur Institute in Paris, which found it in mice and proposed the name of the genus and species of Pneumocystis carinii after Carini.
Pneumocystis was prescribed as a human pathogen in 1942 by two Dutch investigators, van der Meer and Brug, who found it in three new cases: a 3-month-old infant with congenital heart disease and two of 104 cases of autopsies - an infant 4 months and 21 years old. There is only one species described in the genus, they consider the human parasite as P. carinii . Nine years later (1951), Dr. Josef Vanek at Charles University in Prague, Czechoslovakia, showed in a study of lung parts of 16 children that the organism labeled "P. Carinii " is the causative agent of pneumonia in these children. The following year, JÃÆ'rovec reported " P. carinii " as the cause of interstitial pneumonia in neonates. After realizing that Pneumocystis of humans can not infect experimental animals such as rodents, and that the form of rats Pneumocystis differs physiologically and has different antigenic properties, Frenkel is the first to recognize human pathogens as a different species. He named it " Pneumocystis jiroveci " (corrected to P. jirovecii - see the above nomenclature). The controversy is above the re-labeling of P. carinii in humans as P. jirovecii , which is why both names still appear in the publication. However, only the name P. jirovecii is used exclusively for human pathogens, whereas the name P. carinii has had wider applications for many species. Frenkel and the people before he believed that all Pneumocystis were protozoa, but soon after that evidence began to accumulate that Pneumocystis is a genus of fungi. Recent studies show it to be unusual, in some ways the primitive genus Ascomycota, associated with a group of yeast. Each primate tested, including humans, appears to have its own type of Pneumocystis that is unable to infect other host species and has evolved along with each species. Currently, only five species have been officially named: P. jirovecii from humans, P. carinii as the original name of the mouse, P. murina > from rats, P. wakefieldiae also from rats, and P. oryctolagi from rabbits.
Historical and even recent reports about P. carinii from humans are based on older classifications (still used by many people, or they are still debating the recognition of different species within the genus Pneumocystis ) which does not mean that it is actually P. carinii of rats actually infect humans. In the intermediate classification system, different taxa in different mammals have been called formae speciales or forms. For example, the human "form" is called Pneumocystis carinii f. [or f. sp.] hominis , while the original form of mouse infection is called Pneumocystis carinii f. [or f. sp.] carinii . This terminology is still used by some researchers. The species Pneumocystis originally seen by Chagas has not been named as a different species. Many other undescribed species may exist and those that have been detected in many mammals are known only from detection of molecular samples from lung tissue or fluid, not by direct physical observation. Currently, they are indefinite taxa.
References
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