Bacterial Pneumonia in Hematopoietic Stem Cell Transplant Recipients

Due to the complex and persisting immune defects associated with hematopoietic stem cell transplantation (HSCT) and its complications, bacterial pneumonia is an important cause of morbidity and mortality among HSCT recipients. Quantitative and functional impairments of leukocyte-mediated immunity are common following HSCT, placing patients at elevated risk of infection caused by common and opportunistic bacterial pathogens. Further, the risk of bacterial pneumonia is enhanced by patient characteristics such as lung architectural derangements caused by prior cancer treatments, mucositis and other disruptions of epithelial barrier function, impairments of airway protection and/or swallow function, and the presence of graft-versus-host disease. The immune defects present in HSCT patients often attenuate the characteristic clinical signs of bacterial pneumonia, and there are many competing causes of fever, pulmonary infiltrates, and respiratory symptoms. Thus, the diagnosis of bacterial pneumonia is especially challenging in this population, though prompt pathogen identification and initiation of adequate antimicrobial therapy is essential to patient outcomes. This chapter addresses the importance of maintaining a high index of suspicion for bacterial pneumonia following HSCT. It also addresses the value of early imaging and diagnostic testing with emphasis on considering patient-specific immune defects and exposure history in the initial management of post-HSCT bacterial pneumonia.