A Review of 11 Years of Stenotrophomonas Maltophilia Blood Isolates at a Tertiary Care Institute in Canada

Background: Stenotrophomonas maltophilia has emerged as a significant nosocomial pathogen with increasing resistance to trimethoprim/sulphamethoxazole (TMP/SMX), the current drug of choice for treatment.

Objectives: To describe the microbiological and clinical characteristics of S maltophilia bloodstream infections (BSIs) over an 11-year period at a tertiary care centre in Canada.

Methods: All adult S maltophilia BSIs from 1999 to 2009 in a 750-bed tertiary care teaching hospital (University of Alberta Hospital, Edmonton, Alberta) were identified through the infection control nosocomial infection surveillance program. Demographic and clinical data were extracted from the infection control database and from patient charts. Microbiological data were confirmed through the laboratory information system.

Results: Twenty-five episodes of S maltophilia BSI (0.9% of all BSIs) involving 24 patients were identified between 1999 and 2009. The patient age range was 18 to 83 years (average 45.7 years). The majority were men (14 of 24 [58.3%]). The mean length of hospital stay was 83.3 days (range eight to 310 days). The rate of S maltophilia BSIs per 1000 admissions ranged from 0.04 to 0.22 (average 0.09). Greater than one-half of the episodes (13 of 25 [52%]) were admitted to the intensive care unit before BSI onset. Laboratory data were available for 24 of the 25 isolates. Polymicrobial infections were present in 11 of 24 (45.8%) patients. Resistance to TMP/SMX occurred in 8.3% of all infections. Fifteen per cent of isolates were resistant to ticarcillin/clavulanate. Mortality attributed to bacteremia was 16.7%.

Conclusions: In the University of Alberta Hospital, the rate of S maltophilia BSI remains low and constant, and TMP/SMX remains the drug of choice for treatment.