Lower respiratory tract infections (LRTIs) in immunocompromised patients represent a clinical challenge due to the wide diversity of etiologic agents and nonspecific clinical manifestations, which hinder differential diagnosis and limit the effectiveness of empirical therapy. Thus, rapid and accurate detection of etiologic agents allows rationalization of broad-spectrum antibiotic use and reduction of selective pressure associated with emergence of antimicrobial resistance. In this setting, opportunistic pathogens such as Mycobacterium tuberculosis (MTB), Pneumocystis jirovecii (PJ) and cytomegalovirus (CMV), frequently involved in LRTIs, are not detected by conventional microbiological methods. Therefore, molecular diagnostic approaches have emerged as promising tools for differential diagnosis of LRTIs, promoting effective clinical management. The objective of this study was to assess the prevalence of MTB, PJ and CMV in bronchoalveolar lavage (BAL) samples from immunocompromised patients with clinical suspicion of LRTI, using molecular methods, aiming to contribute to differential diagnosis and optimization of clinical management. All qualitative qPCR tests for MTB, PJ and CMV performed on BAL samples between January 2025 and May 2025 were included. A total of 68 tests for CMV were performed, of which 29 (42.6%) were positive, with distribution across different hospital units, including intensive care, medical and surgical wards. Regarding PJ, 16 tests were performed, with 5 positive results (31.3%). For MTB, 125 samples were processed using rapid PCR with detection of rifampicin resistance; of these, 3 (2.4%) were positive, two without rifampicin resistance and one with trace detection and indeterminate resistance. The analysis demonstrates the importance of using molecular methods for early detection of severe pulmonary infections in critically ill patients. The high positivity for CMV highlights the need for epidemiological surveillance in immunosuppressed populations. The low detection of M. tuberculosis suggests targeted use of testing based on clinical suspicion. Systematic use of BAL in combination with molecular diagnostics is a valuable tool for clinical management and control of hospital infections.
Kappaun et al. (Sun,) studied this question.