Pneumocystis jirovecii - Complication, Prognosis, Laboratory Diagnosis, Epidemiology, Reservoir, Transmission, Treatment

Complications of Pneumocystis jirovecii

In rare cases (less than 3%) complications may occur, Pneumocystis jirovecii may disseminate and form extra-pulmonary lesions. Spleen, liver, bone marrow, and lymph nodes may be involved in such cases.

Prognosis of Pneumocystis jirovecii

In case Pneumocystis jirovecii pneumonia (PCP) is untreated, the prognosis is poor as pulmonary damage may lead to death.

Epidemiology of Pneumocystis jirovecii

Epidemiologically, Pneumocystis jirovecii is distributed worldwide- in both humans and animals. Animal hosts include mostly mammals such as sheep, goats, horses, monkeys, guinea pigs, chimpanzees, mice, rats, and rabbits.

Geographically, the fungi have been reported in China, Japan, Iran, Israel, South America, Congo, USA, Canada, Brazil, Australia, Malaysia, New Zealand, and Euro-Asia.

Reservoir, Source of Pneumocystis jirovecii

Infected man or any animal is the main source and reservoir of infection for Pneumocystis jirovecii. A mature cyst is believed to be the infective form of this fungi.

Transmission of Pneumocystis jirovecii

Transmission of Pneumocystis jirovecii takes place by:

• Man-to-man transmission

  since it is an air-borne infection, inhalation of mature cysts via aerosols transmits the infection

• congenital transmission

  maybe caused by Pneumocystis jirovecii infection but is rare

Laboratory diagnosis of Pneumocystis jirovecii

The laboratory diagnosis of Pneumocystis jirovecii begins with the collection of samples:

Sample

• Bronchoalveolar lavage (BAL)

• sputum

• lung biopsy

• transbronchial biopsy

Microscopy

Microscopy is done to demonstrate the presence of Pneumocystis jirovecii in the specimen.

Staining microscopy

Stains such as Giemsa, polychrome methylene blue, methylamine silver, toluidine blue O, and Gram-Weigert stains are used.

• Giemsa and polychrome methylene blue are unreliable as they also stain host tissue sections and may be difficult to interpret

• methylamine silver, toluidine blue O, and Gram-Weigert stains only stain the cell wall of Pneumocystis jirovecii and hence are more reliable

  * However, these stains also stain fungi but not the internal contents of Pneumocystis jirovecii cysts

Since all the above stains cannot differentiate antigenic variants of the fungi, the procedure lack sensitivity.

Immunofluorescence (IF) methods

• it uses monoclonal antibodies

• higher sensitivity than conventional microscopy

Serodiagnosis

• serodiagnostic tests that can be used to diagnose Pneumocystis jirovecii infection include

  Complement Fixation Test (CFT)

  Indirect Fluorescent Antibody (IFA)

  Enzyme-Linked Immunosorbent Assay (ELISA)

  Western Blot

  Counter-current immunoelectrophoresis (CIEP)

  Latex Agglutination Test (LAT)

• uses whole fungi or soluble extracts of fungi as antigens

• does not differentiate between previous and active infection

• can cross-react with Toxoplasma gondii

Molecular diagnosis

The molecular diagnosis of Pneumocystis jirovecii can be done by following methods:

• DNA hybridization

• in situ rRNA hybridization

• PCR

Other methods

• Imaging methods – chest X-ray

• pulmonary function

Treatment of Pneumocystis jirovecii

Treatment of Pneumocystis jirovecii is done by supportive therapy and specific therapy.

Supportive therapy

• aeration by a high concentration of oxygen, blood transfusion, etc

Specific chemotherapy

• Trimethoprim-sulfamethoxazole

• pentamidine

• trimetrexate and folinic acid

• primaquine and clinamycin

• dapsone

Prevention, Control of Pneumocystis jirovecii

Prevention and control of Pneumocystis jirovecii infection can be done by the use of medical-grade masks by immunodeficient individuals.

Populations at risk of infection include:

• premature and/or malnourished infants

• children with primary immunodeficiency

• people with protein malnutrition

• individuals under treatment including immunosuppressive drugs such as corticosteroids for malignancy, organ transplantation, etc

• HIV/AIDS patients