Pathogenic significance of hemorrhagic pneumonia in hematologic malignancy patients with Stenotrophomonas maltophilia bacteremia: clinical and microbiological analysis

Hemorrhagic pneumonia (HP) is known as the clinical manifestation of Stenotrophomonas maltophilia infection, while catheter-related blood stream infection (CRBSI) is the common clinical presentation of S. maltophilia bacteremia (SMB). The purpose of this study is to evaluate the risk factors for mortality in hematologic malignancy patients with SMB and to analyze clinical and microbiological characteristics of HP associated with SMB and CRBSI. SMB cases of patients with a hematologic malignancy were collected from 2006 through 2016. The overall 30-day mortality rate and mortality risk factors were assessed. The expression of major virulence-associated genes from S. maltophilia isolates, which included genes encoding type-1 fimbriae (smf-1), proteases (StmPr1 and StmPr2), and esterase (Smlt3773), from the blood of patients with HP and CRBSI was investigated. The phenotypic and genotypic traits were also compared. A total of 118 cases of SMB were included. The overall 30-day mortality rate was 61.0%. A multivariable analysis showed that HP was the most important risk factor for mortality (adjusted OR = 106.41; 95% CI = 5.18–2184.55). Although no statistical significance was observed in microbiological analysis, isolates from HP have a trend toward a higher protease activity (93.8% vs. 73.3%, P = 0.172). Clinical analysis showed that thrombocytopenia (P = 0.037) and prolonged neutropenia (P = 0.043) were significant factors associated with HP. Our data, which includes hematologic malignancy patients with SMB, suggest that HP is the significant risk factor for mortality and that the unique characteristics of patients and microbes contribute to the pathogenesis.