Pneumonia after Solid Organ Transplantation.

Abstract: Solid organ transplantation (SOT) has significantly increased over the past few decades, with more than 170,000 SOTs performed worldwide in 2023. Although immunosuppressive treatments have improved patient survival, they have also increased the risk of infections among SOT recipients (SOTRs), especially pneumonia. Pneumonia remains one of the leading causes of morbidity and mortality, with respiratory infections contributing to 30 to 70% of deaths in SOTRs, depending on the organ transplanted and the timing of infection. This review summarizes current knowledge on the epidemiology, risk factors, microbial etiology, and clinical manifestations of pneumonia in SOTRs. Temporal patterns of infection are also explored, with early posttransplant infections frequently caused by nosocomial or donor-derived pathogens, and community-acquired infections predominating beyond 6 to 12 months posttransplantation. The lack of robust, SOT-specific guidelines for pneumonia complicates the management of this entity in SOTRs. Most recommendations are based on extrapolations from immunocompetent populations. Furthermore, the lack of large, prospective trials comparing empirical antibiotic strategies in SOTRs limits evidence-based decision-making. Despite these challenges, early initiation of empirical therapy remains crucial to improving outcomes. The review highlights the importance of timely microbiological diagnosis, individualized antimicrobial stewardship, and targeted therapeutic approaches in the context of increasing antimicrobial resistance. Incorporating local epidemiological data and patient-specific risk profiles may enhance the accuracy of diagnosis and support the de-escalation of therapy upon pathogen identification.