Retrospective analysis of Stenotrophomonas maltophilia bacteremia: clinical features, risk factors and therapeutic choices

Background: Stenotrophomonas maltophilia is an important nosocomial pathogen, which is of increasing frequency in blood stream infection, especially in immunocompromised patients. Objectives: Our study aims to investigate the demographics, clinical characteristics, risk factors, drug resistance and treatment choice of Stenotrophomonas maltophilia bacteremia, trying to find out the independent risk factors associated with attributable mortality and investigate appropriate therapeutic choices for Stenotrophomonas maltophilia bacteremia. Method: In this retrospective study of case series, the clinical records and laboratory tests of 95 patients with S. maltophilia bacteremia in the first hospital affiliated to Zhejiang University from January 2009 to May 2015 were reviewed. Data was analyzed using Chi-square test and multiple logistic regressions. P<0.05 was considered statistically significant. Results: A total of 95 patients (60 male, 35 female) were eligible for the study. Median age of the 95 patients was 61 years (range 15-95 years). Forty-three (45.26%) patients had an underlying malignant disease, of which 18 (18.95%) patients had underlying hematologic malignancies. Crude mortality and attributable mortality was 37.89% and 35.79%, respectively. Through multivariate analysis, neutropenia (Odds Ratio [OR] 0.132, 95% Confidence Interval [CI] 0.043-0.405, P<0.001) and mechanical ventilation (OR 0.254, 95% CI 0.089-0.719, P=0.010) were independent factors related to mortality. In vitro susceptibility data revealed that isolates were most sensitive to TMP/SMZ (95.45%) and most resistant to imipenem (97.8%). The most commonly used agent as monotherapy in definite treatment was levofloxacin and cefoperazone. No significant difference (P=0.967) in mortality was seen between monotherapy and combination therapy. Conclusion: Stenotrophomonas maltophilia bacteremia is a critical situation for patients with high attributable mortality. Our results suggest that neutropenia and mechanical ventilation were independent risk factors associated with mortality. We also believe that levofloxacin and tigecycline can be considered promising alternative agents except for TMP/SMZ.