Risk factors for mortality and implications on therapy for Stenotrophomonas maltophilia bacteraemia

Stenotrophomonas maltophilia is an important nosocomial pathogen. Bacteraemia is associated with significant morbidity, despite antibiotic therapy. Optimal treatment strategies for Stenotrophomonas maltophilia bacteraemia remain ill-defined. Thus, we retrospectively examined the clinical presentation, microbiological characteristics, treatment options to identify risk factors for mortality.

We performed a retrospective single-centre analysis of Stenotrophomonas maltophilia bacteraemia from 1 Jan 2012-30 Jun 2024. Data on the clinical presentation, source of infection, microbiological characteristics, treatment strategies and clinical outcomes were tabulated. Risk factors for in-hospital all-cause mortality were identified by appropriate univariate and multivariable analyses.

There were 197 bacteraemia episodes. In-hospital mortality was 41.6 % (n = 82), and did not change significantly over the years. Patients who died were more likely to have prior carbapenem exposure (81.7 % vs 53.0 %, p < 0.001), presentation in an intensive care (ICU) setting (73.2 % vs 15.7 %, p < 0.001), and had a longer duration of fever (8.5 ± 2.5 vs 3.0 ± 3.8 days, p < 0.001). Microbiological isolation from additional sites other than the blood (e.g. sputum culture positivity) also correlated with mortality (39.0 % vs 7.8 %, p < 0.001). Over time, proportion of isolates resistant to fluoroquinolones increased. An initial antimicrobial choice containing trimethoprim-sulfamethoxazole appeared to be more likely to be associated with survival. Only 13 patients (6.6 %) received dual antibiotics initially, so it was unclear if this was associated with better outcomes. On multivariable analysis, ICU onset, elevated C-reactive protein, longer duration of fever and an absence of intervention for source control remained independently associated with mortality.

Source control of infection may be critical in improving survival in Stenotrophomonas maltophilia bacteraemia. Future prospective studies should validate important risk factors for mortality and define optimal antimicrobial treatment strategies.