Stenotrophomonas maltophilia Infections: Clinical Characteristics and Factors Associated with Mortality of Hospitalized Patients

Purpose: To study the clinical characteristics and factors associated with mortality of patients who had Stenotrophomonas maltophilia infections.

Patients and methods: We conducted a retrospective study to determine the clinical characteristics and factors associated with mortality for S. maltophilia infections among hospitalized adult patients at Siriraj Hospital. The clinical and microbiological data were collected from medical records December 2013-December 2016.

Results: Of 1221 subjects whose clinical samples grew S. maltophilia, 213 were randomly selected for chart review. One hundred patients with a true infection were analyzed. Their median age was 66 years; 47 were males; 46 were critically ill with a median APACHE II score of 18 (2-32); and 91 received antibiotic treatment, mainly with carbapenems (56%), before being diagnosed with a S. maltophilia infection. Pulmonary (53%) and bloodstream infections (25%) were the most common infections. The median length of hospitalization was 19 days before infection onset. The in-hospital mortality rate was 54%. The following factors were associated with mortality: a pre-existing respiratory infection (OR 6.28, 1.33-29.78; p.021); critical illness (OR 3.33, 1.45-7.62; p.005); multi-organ dysfunction (OR 2.44, 1.05-5.70; p.039); being on mechanical ventilation (OR 4.44, 1.90-10.39; p.001); concurrent immunosuppressive therapy (OR 2.67, 1.10-6.47; p.029); intravascular (OR 4.43, 1.79-10.92; p.001) and urinary catheterization (OR 4.83, 1.87-12.47; p.001); and serum albumin <3 g/dL (OR 4.13, 1.05-16.33; p.043). A multivariate analysis identified two independent factors associated with mortality: being on mechanical ventilation (OR 4.43, 1.86-10.59; p 0.001) and receiving concurrent immunosuppressive therapy (OR 2.26, 1.04-6.82; p 0.042).

Conclusion: S. maltophilia can cause nosocomial infections with high mortality, particularly in patients with a prolonged hospitalization. Concurrent immunosuppressive therapy and being on mechanical ventilation are the independent factors associated with a fatal outcome.