Pneumocystis jirovecii: Difference between revisions
From IDWiki
Pneumocystis jirovecii
(added Pathophysiology) |
(→: added cell wall stuff) |
||
| Line 5: | Line 5: | ||
* Yeast-like fungus in the Ascomycota phylum |
* Yeast-like fungus in the Ascomycota phylum |
||
* Has not been able to be grown in culture, and species within the genus have tropism for their specific host |
* Has not been able to be grown in culture, and species within the genus have tropism for their specific host |
||
* It's cell wall lacks ergosterol, so has inherent resistance to many antifungals |
|||
* β-1,3 glucan, however, is an important cell wall component |
|||
* The major immunogenic protein is major surface glycoprotein (Msg), or gpA |
|||
=== History === |
|||
* ''P. jirovecii'' was previously thought to be ''P. carinii'', but it was later realized that they were two species within the same genus |
* ''P. jirovecii'' was previously thought to be ''P. carinii'', but it was later realized that they were two species within the same genus |
||
** ''P. carinii'' and ''P. wakefieldiae'' infect rats, ''P. murina'' infects mice and ''P. jiroveci'' infects humans |
** ''P. carinii'' and ''P. wakefieldiae'' infect rats, ''P. murina'' infects mice and ''P. jiroveci'' infects humans |
||
Revision as of 23:39, 25 September 2019
- Opportunistic fungal infection of the lower respiratory infection
Microbiology
- Yeast-like fungus in the Ascomycota phylum
- Has not been able to be grown in culture, and species within the genus have tropism for their specific host
- It's cell wall lacks ergosterol, so has inherent resistance to many antifungals
- β-1,3 glucan, however, is an important cell wall component
- The major immunogenic protein is major surface glycoprotein (Msg), or gpA
History
- P. jirovecii was previously thought to be P. carinii, but it was later realized that they were two species within the same genus
- P. carinii and P. wakefieldiae infect rats, P. murina infects mice and P. jiroveci infects humans
- Also previously thought to be a protozoan, but reclassified as fungus based on phylogenetic analysis, most closely related to Schizosaccharomyces pombe
Epidemiology
- Worldwide distribution
- Only circulates within humans
- Most children have been exposed by age 2 or 3
- Children and immunocompromised patients being the reservoir
- Includes asymptomatic carriage by patients with HIV, malignancy, and long-term steroid use, and in pregnant women
- Risk factors for infection:
- HIV
- Immune-suppression, e.g. from steroids
Pathophysiology
- After inhalation of cyst, trophic forms are released and adhere to type I pneumocytes in the alveolar epithelium
- The immune response involves a combination of humoral and cell-mediated immunity
- Alveolar macrophages are the first response, but require CD4 cells to respond fully
- IgM antibodies recognize common fungal carbohydrate antigens
- CD4 cells are important for the memory response
- The alveolus fills with Pneumocystis
- The inflammatory response may damage the lung
Presentation
- Shortness of breath on exertion
Investigations
- CXR
- Typical: bilateral diffuse patchy disease
- Atypical:
- Normal (15%)
- Localized
- Pneumothorax
- Upper lobe, if on pentamidine
- LDH increased
- CBC often normal
Diagnosis
- Induced sputum or brochoalveolar lavage (normal sputum not sensitive enough)
- 6min walk test: will desaturate, even if well-oxygenated at rest
Treatment
- Septra 5-6mg/kg po BID for 3 weeks
- If pO2 <70mmHg or A-a gradient ≥35: prednisone
- Alternative: clindamycin-primaquine or IV pentamidine
- Duration is 21 days (3 weeks)
Prophylaxis
- Usually instituted if the risk of PJP is greater than 3.5% per year
References
- ^ Po-Yi Chen, Chong-Jen Yu, Jung-Yien Chien, Po-Ren Hsueh. Anidulafungin as an alternative treatment for Pneumocystis jirovecii pneumonia in patients who could not tolerate Trimethoprim/sulfamethoxazole. International Journal of Antimicrobial Agents. 2019. doi:10.1016/j.ijantimicag.2019.10.001.
- ^ L. Cooley, C. Dendle, J. Wolf, B. W. Teh, S. C. Chen, C. Boutlis, K. A. Thursky. Consensus guidelines for diagnosis, prophylaxis and management ofPneumocystis jiroveciipneumonia in patients with haematological and solid malignancies, 2014. Internal Medicine Journal. 2014;44(12b):1350-1363. doi:10.1111/imj.12599.
- ^ N. Goto, S. Oka. Pneumocystis jirovecii pneumonia in kidney transplantation. Transplant Infectious Disease. 2011;13(6):551-558. doi:10.1111/j.1399-3062.2011.00691.x.
