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Pneumocystis pneumonia (PcP) caused by Pneumocystis jirovecii is one of the most common and serious opportunistic infections in immunocompromised patients. People at risk for developing Pneumocystis pneumonia include human immunodeficiency virus positive individuals, cancer patients, people receiving immunosuppressive therapy, organ transplant recipients and people with compromised immune systems. Despite effective treatment and prophylaxis, mortality is reported to be between 15-40%, even in people with immunodeficiency other than acquired immunodeficiency syndrome. Although the number of immunosuppressed patients is increasing, diagnostic and epidemiological studies for this agent are still insufficient. This study aimed to investigate the prevalance and epidemiological characteristics of P.jirovecii isolated from various patient groups. Among the 469 bronchoalveolar lavage fluids or sputum samples sent to the medical microbiology laboratory from various units, 114 samples were selected for indirect fluorescent antibody (IFA) testing and molecular studies based on an examination of the patients' files to determine underlying diseases, use of immunosuppressive drugs, corticosteroid treatments received and the presence of patchy or nodular ground-glass opacity on computed tomography scans and the presence of a cyst-like structure on May-Grunwald Giemsa staining. The presence of P.jirovecii was investigated by IFA and polymerase chain reaction methods and genotyping was performed by sequencing of mtLSU rRNA and internal transcribed spacer (ITS) region. The obtained ITS gene region DNA sequences were aligned and TCS network analysis was performed in the aligned region. As a result, positivity was found in eight samples out of 469 samples by using mtLSU rRNA genotyping, Genotype 1 (n= 3; 37.5%) was found to be the most common genotype in our samples. Genotype 2 (n= 2, 25%), genotype 4 (n= 2, 25%) and genotype 3 were the most frequently detected other genotypes, respectively. When the relationships between the sequences were examined, it was observed that our samples were generally related to the samples originating from Iran. In the present study, the genotyping analysis of the ITS region, constructed using the consensus sequence employed in the study by Lee et al., revealed that the most common genotype was Eh (n=3; 42.85%), followed by Bg (n= 2; 28.57%), Bi (n= 1; 14.28%) and Eg (n=1; 14.28%). Our study is the first genotyping study conducted in our country using the ITS gene region. Different epidemiological findings were found in P.jirovecii genotype frequencies in studies conducted in different geographies. This suggests that genetic variations in P.jirovecii have a geographical component and this may affect the distribution of P.jirovecii strains among humans. According to TCS network analysis, our samples are generally associated with samples originating from Iran. None of our samples are found alongside samples originating from India. However, in certain areas of the analysis, New World and Old-World samples exist together. It can be assumed that globalization and thus the increase in human movement over time has led to the spread of different genotypes to different geographical regions and the formation of genotypic mosaics in certain geographical regions. Man-made destruction of nature and the consequent intertwining of urban and rural boundaries, as well as global warming and climate change have undeniably contributed to these movements.