Stenotrophomonas maltophilia Bloodstream Infection Outbreak in Acute Care Hospital, California, USA, 2022–20231

Stenotrophomonas maltophilia is an opportunistic bacterial pathogen found in healthcare settings. During May 2022-September 2023, an acute care hospital in northern California, USA, identified 13 S. maltophilia bloodstream infections among intensive care unit patients. Whole-genome sequencing showed the isolates were highly related. We identified risk factors for infection by conducting a matched case-control study, targeted assessment of infection prevention and control practices, and laboratory testing of suspected environmental reservoirs. Among 13 case-patients and 39 control-patients, patients exposed to iodinated contrast (odds ratio [OR] 12.0; 95% CI 2.1-∞), injectable propofol (OR 12.2; 95% CI 1.5-101.4), or fentanyl (OR 9.2; 95% CI 1.8-∞) had increased odds of S. maltophilia bloodstream infection. Although we did not have culture confirmation of a source, we suspect S. maltophilia was transmitted by exposure to nonsterile water from a common source. We recommended infection prevention and control practices to reduce risk for contamination from nonsterile water.