Hospital-acquired Stenotrophomonas maltophilia Infections: Epidemiology and Risk Factors for Mortality

Introduction: Nosocomial Stenotrophomonas maltophilia infections have become a major concern in the recent years. In this study, we aimed to evaluate the clinical characteristics of nosocomial S. maltophilia infections and assess the risk factors for mortality. Materials and Methods: An active and laboratory-based surveillance of hospital-acquired infections is conducted by the Infection Control Committee in high-risk and intensive care units of our hospital. In this study, these surveillance data were used to evaluate hospital-acquired S. maltophilia infections. Results: In this study, 97 patients with hospital-acquired S. maltophilia infection were evaluated. Pneumonia (47.5%) and bacteremia (37.1%) were the most common types of infection. Hematologic malignancies, solid tumors, and chronic heart diseases were the most common underlying conditions. Central venous catheters, mechanic ventilation and immunosuppression were frequent risk factors in patients. Previous carbapenem use was common (78.4%). Seven-day and 28-day mortality were 25.7% and 46.3%, respectively. In the univariate analysis, hospital-acquired pneumonia was associated with seven-day mortality. Age, central line-associated bloodstream infections, ventilator-associated pneumonia, hospital-acquired pneumonia, mechanical ventilation and the presence of a urinary catheter were associated with 28-day mortality in univariate analysis. Age and hospital-acquired pneumonia were independently associated with 28-day mortality in the multivariate analysis. The treatment regimens did not have any impact on mortality. Tigecycline (5.6%), levofloxacin (7%), and trimethoprim-sulfamethoxazole (8.5%) exhibited the lowest resistance rates. Conclusion: S. maltophilia is a nosocomial agent that mainly affects the critical and immunosuppressive patients. Pneumonia and bacteremia are the most common infection sites, leading to significant mortality. Age and presenting with hospital-acquired pneumonia are independent risk factors for mortality. Tigecycline has the lowest resistance rate among all antibiotics and it may be a good alternative for treatment. Although resistance to levofloxacin and trimethoprim-sulfamethoxazole is not high, it should be closely monitored.