Treatment of Stenotrophomonas malthophilia bloodstream infections from guidance to real life: multicenter retrospective cohort study

Objectives: Infectious Diseases Society of America guidance recommend the use of combination therapy (CT) for the treatment of Stenotrophomonas maltophilia (SM) infections. The aims of our study are to describe therapeutical management of patients with SM bloodstream infections (SM-BSI) and to evaluate the impact of antibiotic CT compared to monotherapy (MT) on 30-days mortality. Methods: Multicenter, retrospective study of patients with SM-BSI hospitalized in 14 centers between January 2021–December 2022. Multivariable logistic regression analysis was performed to assess the risk factors for 30-days mortality including CT therapy as main exposure. To address potential confounding, an inverse probability of treatment weighting (IPTW) approach was used. Results: 64 patients with SM-BSI analyzed: 32 (50 %) male, median age of 65 years (IQR: 55–75). MT was administered in 49 patients (76.6 %) and CT in 15 (23.4 %). Trimethoprim/sulphamethoxazole was the most frequent drug used in both MT and CT. Levofloxacin was the second preferred MT. Patients receiving CT were more frequently admitted in ICU with septic shock at BSI onset. At multivariable analysis, septic shock (OR: 7.65, 95 %CI: 1.32–44.48, p = 0.023) and haematological malignancies (OR: 6.82, 95 %CI: 1.50–30.88, p = 0.013) were independent risk factors for 30-day mortality. Using an IPTW-based multivariable analysis, CT showed a non-significant trend toward a protective effect on 30-day mortality (OR: 0.88; 95 % CI: 0.23–3.42; p = 0.855). Conclusions: CT for SM-BSI is used in a minority of cases in our cohort, representing the worst clinical scenarios. Further evidence is needing to confirm the impact of CT on outcome.