Polymicrobial pulmonary infection in patients with hematological malignancies: prevalence, co-pathogens, course and outcome

Purpose: The frequency and clinical significance of polymicrobial pneumonia in patients with hematological malignancies (HM) are poorly understood. The aim of the present study is to describe the prevalence, risk factors, clinical characteristics, and outcome of patients with HM and polymicrobial pneumonia.

Methods: Over a 5 year period, 436 consecutive adult patients with HM and pulmonary infiltrates underwent diagnostic fiberoptic bronchoscopy with bronchoalveolar lavage. For 219 patients an infectious etiology was diagnosed, of them 45 (20.5 %) had polymicrobial etiology. Risk factors, clinical course and outcome of polymicrobial pulmonary infection in patients with HM were established.

Results: 45 patients with HM were identified with polymicrobial pulmonary infection, 39 of them with two pathogens, and 6 with three. The most common co-pathogen identified was Aspergillus sp. (87 %). Allogeneic hematopoietic stem cell transplantation (HSCT) and graft versus host disease (GVHD) were predictors of polymicrobial infection. Compared to patients with monomicrobial pneumonia, patients with polymicrobialpulmonary infection had a more severe clinical course with more dyspnea (69 vs. 49 %, P = 0.016), hemoptysis (16 vs. 7 %, P = 0.065) and more required respiratory support (27 vs. 17 %, P = 0.125). In-hospital mortality was significantly higher in patients with polymicrobial pulmonary infection than in patients with monomicrobial pulmonary infection (49 vs. 19 %, P < 0.001).

Conclusions: Polymicrobial pulmonary infection occurs quite frequently in patients with HM, especially in allogeneic HSCT recipients and in patients with GVHD. The clinical course of polymicrobial pulmonary infection is severe and mortality approaches 50 %. The clinician taking care of these patients should always look for additional copathogens in profoundly immunosuppressed patients with pneumonia.