Molecular Identification and Genotyping of <i>Pneumocystis jirovecii</i> in Bronchoalveolar Lavage (BAL) Samples of Patients Admitted to the Intensive Care Unit of Eastern Iran

Background: Pneumocystis jirovecii is an opportunistic fungal pathogen primarily affecting immunocompromised individuals, leading to Pneumocystis pneumonia (PCP). The increasing occurrence of PCP in intensive care units (ICUs) demands prompt diagnostic measures. Objectives: This study aims to molecularly identify P. jirovecii in bronchoalveolar lavage (BAL) samples from ICU patients in eastern Iran. Methods: This descriptive study was conducted from May 2023 to January 2024, involving 100 BAL samples from ICU patients at Waliasr Hospital, Birjand University of Medical Sciences. Demographic and clinical data were collected through a checklist. DNA was extracted using the Favorgen Biotech DNA Tissue Kit, and nested-polymerase chain reaction (PCR) targeting the 18S rRNA gene was performed to detect P. jirovecii. Sequencing was conducted using the Applied Biosystems Big Dye terminator cycle sequencing kit. Results: Among the 100 patients examined, 9 (9%) tested positive for P. jirovecii, predominantly in individuals aged 61 to 80 years (66.7%). The most common underlying conditions were hypertension (66.7%) and diabetes (33.3%). The primary hospitalization reasons for positive cases included sepsis and neurological conditions. Genotyping revealed that the majority of positive samples belonged to genotype III. Conclusions: The findings underscore the high prevalence of P. jirovecii in critically ill patients, particularly among older adults with comorbidities. The study highlights the importance of rapid molecular diagnostics in patients admitted to the ICU to improve management and outcomes. The identification of genotype III as the dominant strain necessitates ongoing surveillance to monitor treatment efficacy and resistance patterns.