Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 5 4 2013 12 15 411 417 EN Maryam-Fatemeh Sheikholeslami Mycobacteriology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran ; Tarbiat Modares University, Medical Faculty, Parasitology department, Tehran, Iran. Javid Sadraei Tarbiat Modares University, Medical Faculty, Parasitology department, Tehran, Iran. Parissa Farnia Mycobacteriology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran. Mehdi Forozandeh Tarbiat Modares University, Medical Faculty, Biotechnology department, Tehran, Iran. Hamid Emadi Kochak Iranian HIV/AIDS Research Center, Imam Khomini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Payam Tabarsi Mycobacteriology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran. Seyed Alireza Nadji Virology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran. Majid Pirestani Tarbiat Modares University, Medical Faculty, Parasitology department, Tehran, Iran. Mohammad-Reza Masjedi Chronic Respiratory Disease Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran. AliAkbar Velayati Mycobacteriology Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran ; Chronic Respiratory Disease Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran. 2015 10 16 Background and Objectives: With increasing rate of immunodeficiency diseases in the world, opportunistic micro-organism such as Pneumocystis jirovecii (P. jirovecii) become more important. Little information is available on prevalence of this life- threatening microorganism in Iran. This study was designed to determine the colonization and the rate of active disease caused by P. jirovecii in two groups of Iranian immunosuppressed patients. Materials and Methods: Two hundred and fifty five pulmonary samples were collected from two groups of immunosuppress- ed patients to detect a 260bp fragment of mt LSU rRNA gene of P. jirovecii by nested PCR. The first group was COPD patients consumed oral, inhaled or injectable corticosteroid and the second group was patients with malignancies under chemotherapy. Both groups were referred to National Research Institute of Tuberculosis and Lung Disease and Imam Khomeini hospital because of pulmonary symptoms. All patients introduced to this project were confirmed HIV sera-negative by ELISA and western blot test. Results: The mean age of COPD patients was 66.5 ± 11 (41-88) years and all of them were men. The mean age of patients with malignancy (PMs) was 43 ± 11 (23-65) years and 51.6% were men. The P. jirovecii was colonized in 7 of 89 COPD patients (7.9%) and its DNA was isolated from 11 of 153 PMs (7.2%). The microorganism could cause active disease in 7 of 67 (10.5%) PMs who suffered from pneumonia. Conclusion: The study showed that P. jirovecii was one of colonizing agents in the COPD patients, but it could cause active disease in PMs. Generally, the microorganism can exist in the lung of non-HIV+  immunosuppressed patients. Therefore, it should be considered as a potential infective agent in non-HIV+ immunocompromised patients. https://ijm.tums.ac.ir/index.php/ijm/article/view/486 https://ijm.tums.ac.ir/index.php/ijm/article/download/486/262