Two consecutive outbreaks of Stenotrophomonas maltophilia (Xanthomonas maltophilia) in an intensive-care unit defined by restriction fragment-length polymorphism typing

OBJECTIVE: To investigate and control consecutive outbreaks of Stenotrophom onas maltophilia infections in intensive-care-unit (ICU) patients. DESIGN: Epidemiological investigation; restriction fragment-length polymorp hism typing by pulsed-field gel electrophoresis (PFGE) of genomic DNA of ou tbreak strains; institution of infection control measures to limit spread. SETTING: The medical-surgical ICU in an 800-bed tertiary-care center in Cal gary, Alberta, Canada. RESULTS: S maltophilia was recovered from 14 ICU patients (12 infected, 2 c olonized) between February 1993 and February 1994. Ten of the 14 patient is olates 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 fi-om a ventilator being used by a patient not infected with S maltophilia also were identical, but diff erent from the first 6. The ventilator isolate was temporally associated wi th the latter 4 patients. CONCLUSION: Molecular typing allowed us to determine that there were two se parate 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.