Retrospective Singapore cohort links S. maltophilia bacteremia with higher mortality than P. aeruginosa and A. baumannii

A retrospective cohort study at Singapore General Hospital found that adults with bloodstream infections caused by Stenotrophomonas maltophilia had higher in-hospital and one-year mortality than patients with Pseudomonas aeruginosa or Acinetobacter baumannii bacteremia. The study included 901 adults with monomicrobial bacteremia treated at the hospital from January 2018 through June 2025: 587 had P. aeruginosa, 163 had A. baumannii, and 151 had S. maltophilia.

According to the study abstract, in-hospital mortality was 43.0% among patients with S. maltophilia, compared with 29.5% to 31.3% for the other two pathogens; the difference was statistically significant at p < 0.001. One-year mortality was also higher for S. maltophilia, at 45.7% versus 34.9% to 36.2% for P. aeruginosa and A. baumannii (p = 0.049). The authors also reported substantially greater years of potential life lost for S. maltophilia bacteremia, with a geometric mean of 15.4 years (p < 0.001).

Patient characteristics differed among the three groups. Patients with S. maltophilia bacteremia had a mean age of 61.5 years and higher recorded rates of central venous catheter use, reported in 78.1% of cases, and neutropenia, reported in 25.2%. Acquired resistance was less prevalent in the S. maltophilia group, at 27.2%, than in A. baumannii, at 52.1%, or P. aeruginosa, at 34.2% (p < 0.001). The abstract defines acquired resistance for S. maltophilia as non-susceptibility to levofloxacin, cotrimoxazole or minocycline, while for the other pathogens it refers to non-susceptibility to one or more agents in standard antipseudomonal or antimicrobial categories, using Clinical and Laboratory Standards Institute breakpoints.

Appropriate empirical therapy was reported for 67.5% of patients with S. maltophilia, 62.6% of those with A. baumannii, and 85.5% of those with P. aeruginosa (p < 0.001). Multivariable logistic regression estimated that appropriate empirical therapy was associated with lower mortality at all assessed timepoints, with the strongest association at 30 days (adjusted odds ratio 0.42, p = 0.002). The authors stated that the lower rate of appropriate empirical therapy for S. maltophilia was consistent with a contribution from delayed effective therapy, but the observational design does not establish that treatment timing caused the mortality differences. As a single-center retrospective study summarized here from its abstract, the findings are limited in their ability to separate organism-specific effects from differences in patient characteristics, treatment selection and other clinical factors. The authors stated that prospective studies are required to determine whether earlier organism identification or risk-stratified empirical treatment improves clinical outcomes.

Subject of Research: Comparative clinical outcomes of three non-fermenting Gram-negative pathogens in adult bacteremia

Article Title: Comparative analysis of clinical outcomes in non-fermenting gram-negative bloodstream infections: Stenotrophomonas maltophilia versus Pseudomonas aeruginosa and Acinetobacter baumannii in Asian Tertiary Care

Article References: Yang, Y., Lai, D. C. M., Foo, M. Z. Q., Low, C. T., Tan, Y. E., Aung, M. K., Aung, M. O., Arora, S., Chan, D. Y. W., Wee, I. L. E., Sim, J. X. Y., Sridharan, S., Chlebicki, M. P., & Venkatachalam, I. (2026). Comparative analysis of clinical outcomes in non-fermenting gram-negative bloodstream infections: Stenotrophomonas maltophilia versus Pseudomonas aeruginosa and Acinetobacter baumannii in Asian Tertiary Care. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14658-9

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DOI: 10.1186/s12879-026-14658-9

Keywords: S. maltophilia, P. aeruginosa, A. baumannii, bacteremia, bloodstream infections, mortality, empirical therapy, antimicrobial resistance, retrospective cohort, Singapore, Comparative, analysis