To investigate and control consecutive outbreaks of Stenotrophomonas maltophilia infections in intensive-care–unit (ICU) patients.

Epidemiological investigation; restriction fragment-length polymorphism typing by pulsed-field gel electrophoresis (PFGE) of genomic DNA of outbreak strains; institution of infection control measures to limit spread.

The medical-surgical ICU in an 800-bed tertiary-care center in Calgary, Alberta, Canada.

S maltophilia was recovered from 14 ICU patients (12 infected, 2 colonized) between February 1993 and February 1994. Ten of the 14 patient isolates and 1 environmental isolate were available for PFGE typing. Patient isolates from 6 of the first 10 patients were identical. Isolates from the next 3 of 4 patients and an isolate recovered from a ventilator being used by a patient not infected with S maltophilia also were identical, but different from the first 6. The ventilator isolate was temporally associated with the latter 4 patients.

Molecular typing allowed us to determine that there were two separate consecutive S maltophilia outbreaks rather than a single protracted outbreak. Recovery of S maltophilia from patient ventilators and an in-line suction catheter suggests that the organism may have been spread by cross-contamination from contaminated equipment or from an environmental source.