Academic journal article Iranian Journal of Public Health

Pneumocystis Jirovecii Colonization in Non-HIV-Infected Patients Based on Nested-PCR Detection in Bronchoalveolar Lavage Samples

Academic journal article Iranian Journal of Public Health

Pneumocystis Jirovecii Colonization in Non-HIV-Infected Patients Based on Nested-PCR Detection in Bronchoalveolar Lavage Samples

Article excerpt

Abstract

Background: Pneumocystis jirovecii causes Pneumocystis pneumonia (PCP) in immunocompromised patients with a high rate of morbidity and mortality. Colonization with this fungus may stimulate pulmonary inflammation or lead to PCP in susceptible patients. The epidemiology of this infection and routs of its transmission has poorly studied in Iran. We examined Pneumosystis colonization in patients with various lung underlying diseases.

Methods: Bronchoalveolar lavage (BAL) fluids of 458 patients with different underlying diseases or pulmonary signs were collected between August 2010 and January 2012. Patients were divided into four groups: transplant recipients, malignant patients, immunosuppressive drug recipients and patients with other different lung diseases. A sensitive nested-PCR method targeted 18S ribosomal RNA gene was used for investigating P. jirovecii in the specimens.

Results: P. jirovecii DNA was detected in 57 out of 458 (12.5%) BAL samples by nested-PCR. Colonization rate in malignant patients, transplant recipients, immunosuppressive therapy recipients and patients with other various lung diseases was 21.7%, 20.3%, 12.7% and 7.3%, respectively. The enzyme BanI cuts all PCR products producing frag-ments with the size of 228 and 104 base pair. This finding as well as sequencing of four random positive samples vali-dated and reconfirmed the PCR results. P. jirovecii cysts were found in 5 out of 57 PCR positive samples.

Conclusion: A significant number of patients with pulmonary diseases were colonized by P. jirovecii that can develop to PCP in these patients or they may transmit the fungus to other susceptible patients.

Keywords: Pneumocystis jirovecii, Pneumocystis pneumonia, Colonization, Nested-PCR

Introduction

Pneumocystis jirovecii (previously called Pneumocystis carinii) is an unusual opportunistic fungus that was formerly considered as a protozoon. However, con-sidering sequence homologies in 18S ribosomal RNA gene, this organism was reclassified to the class Archiascomycetes, phylum Ascomycota of the fungal kingdom (1, 2). P. jirovecii causes pneumocystis pneumonia (PCP) in immunodeficient patients es-pecially in HIV infected persons and other larger immunosuppressed groups such as transplant recipi-ents, patients with autoimmune disorders (who treated with steroid or monoclonal antibodies di-rected against cell mediated immune system media-tors), malignant patients and malnourished children (1, 3-5). In the lack of a culture system for isolating P. jirovecii from clinical samples, the laboratory diagno-sis of PCP has depended on microscopic detection of organism with conventional staining methods like toluidine blue O, Grocott-Gomori methenamin sil-ver, Giemsa, Calcofluor White or direct and indirect fluorescence immunocytochemical staining (6-8).

Recently PCR technology has improved sensitivity of the diagnosis of PCP and reduced need to inva-sively obtained clinical specimens such as lung biopsy. Nested-PCR approach has made detection of P. jirovecii from non-invasive clinical samples such as induced sputa or oropharyngeal washings more sensitive and specific than single-step stan-dard PCR (7, 9). By application of these tech-niques, colonization with P. jirovecii have been demonstrated in some groups of patients with mild immunosuppression (10). These techniques have also shown that P. jirovecii can be carried in normal healthy individuals or asymptomatic pa-tients with only mild immunosuppression induced by HIV infection or in patients requiring long term glucocorticoid therapy for underlying malig-nancy, and in immunocompetent individuals with chronic pulmonary diseases (7, 8). The coloniza-tion may surrogate to PCP on the conditions that underlying diseases go to a severe stage or in the absence of correct treatments. For this reason de-tection of carriage or colonization could be im-portant for understanding the nature of epidemio-logical or clinical aspects of PCP. …

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