Colonization by Pneumocystis jirovecii and Its Role in Disease

Abstract

SUMMARY Although the incidence of Pneumocystis pneumonia (PCP) has decreased since the introduction of combination antiretroviral therapy, it remains an important cause of disease in both HIV-infected and non-HIV-infected immunosuppressed populations. The epidemiology of PCP has shifted over the course of the HIV epidemic both from changes in HIV and PCP treatment and prevention and from changes in critical care medicine. Although less common in non-HIV-infected immunosuppressed patients, PCP is now more frequently seen due to the increasing numbers of organ transplants and development of novel immunotherapies. New diagnostic and treatment modalities are under investigation. The immune response is critical in preventing this disease but also results in lung damage, and future work may offer potential areas for vaccine development or immunomodulatory therapy. Colonization with Pneumocystis is an area of increasing clinical and research interest and may be important in development of lung diseases such as chronic obstructive pulmonary disease. In this review, we discuss current clinical and research topics in the study of Pneumocystis and highlight areas for future research.

Investigation of Pneumocystis jirovecii Pneumonia and Colonization in Iatrogenically Immunosuppressed and Immunocompetent Patients

“…Epidemiyolojik ve klinik çalışmalar, P.jirovecii kolonizasyonu saptanan kişilerin, etkenin yayılmasında rezervuar rolü oynayabileceğini, immün süpresyon durumunda ise mevcut kolonizasyonun PCP gelişim riski oluşturduğunu ortaya koymuştur 7,10,25 . Çalışmamızda nPCR ile pozitif saptanan 18 (%19.6) hasta "P.jirovecii kolonizasyonu" olarak değerlendi-rilmiştir.…”

“…Bununla birlikte AIDS dışı immünosüp-resif hastalarda gözlenen PCP'de parazit yükünün çoğu zaman düşük olması, mikroskopik tanının duyarlılığını azaltmaktadır 4,7 . Günümüzde bu sorun PCR temelli yöntemlerin kullanıma girmesiyle önemli ölçüde aşılmış durumdadır 2,8 .…”

“…Ancak klinik örneklerde P.jirovecii'nin veya DNA'sının saptanması mutlaka enfeksiyon anlamına gelmemektedir. Klinik olarak semptom vermeyen kişilerde, organizmanın veya DNA'sının tespit edilmesi kolonizasyon olarak tanımlanmıştır 7,9 . Bu nedenle mikroskopisi negatif, ancak PCR pozitif bulunan hastalarda enfeksiyonun tanısı ve tedavisi için klinik değerlendirme oldukça önemlidir.…”

Impact of HIV infection and smoking on lung immunity and related disorders

“…Notably, colonisation with P. jirovecii has been reported in patients with various chronic lung diseases, and aside from being involved in the development or transmission of this infection, may also be associated with the development of other lung conditions, such as lung cancer [142]. Some studies have documented high rates of colonisation with P. jirovecii in patients with lung cancer; one small study noted a colonisation rate of 100% in patients with small cell carcinoma, as compared to nonsmall cell cancer [142].…”

Pneumocystis Pneumonia Associated with Human Immunodeficiency Virus

“…In the majority of hosts with an intact immune system the organism is rapidly coughed out. If the host has any underlying "minor" immune suppression/HIV-associated immunodeficiency, colonization with Pneumocystis ensues [34] [35]. If the host then becomes more immune compromised, by progression of HIV, or by additional therapeutic immune supression then Pneumocystis propagates within the alveoli, and slowly "floods them out."…”