Pseudooutbreak of Stenotrophomonas maltophilia bacteremia in a general ward

BackgroundStenotrophomonas maltophilia is a significant nosocomial pathogen and is commonly isolated in the hospital environment. We investigated the risk factors for a bloodstream pseudooutbreak of S maltophilia in a general ward.MethodsOn November 24 and 25, 2005, 7 patients without evidence of sepsis were reported as positive for blood culture with S maltophilia from blood samples collected on November 21 and 22, 2005. We conducted an epidemiologic investigation and a case-control study of this pseudooutbreak.ResultsAll 7 S maltophilia showed the same antibiogram and an indistinguishable pattern on pulsed-field gel electrophoresis. The observational study revealed multiple lapses in infection control, including multiple use of a single bottle of saline for dilution of antibiotics. A case-control study showed that one health care worker, who collected blood samples from 6 of 7 patients, was a significant risk factor for the pseudooutbreak of S maltophilia (P < .05).ConclusionWe suggest that the combination of multiple lapses in infection control and the blood-collecting behavior of a health care worker might be the cause of the pseudooutbreak of S maltophilia.