Outbreak of Stenotrophomonas maltophilia on an intensive care unit.

BACKGROUND: Stenotrophomonas maltophilia causes opportunistic infections and remains a problem pathogen on intensive care unit (ICU) due to its multidrug resistance. AIM: An outbreak of S. maltophilia on ICU is described in order to highlight the risk from contaminated devices for supply of drinking water.
METHODS: The outbreak was investigated by a combination of epidemiology, environmental sampling and molecular typing.
FINDINGS: From 2009 to 2011 isolates of S. maltophilia from 23 patients were found to belong to only two genotypes by contrast with isolates from 52 other patients during this period, which represented distinct strains. The monthly incidence for all S. maltophilia strains ranged from 0 to 11% and for the two outbreak strains from 0 to 9%. Admission and weekly pharyngeal screening on ICU showed that the outbreak strains were acquired on ICU (range: 3-90 days). The majority of isolates (74%) were from the respiratory tract. Only two of 12 (17%) colonized intubated patients developed pneumonia. Environmental sampling found the two outbreak strains in two sinks and in the drinking water of the cooling unit in the ICU kitchen. S. maltophilia had formed a biofilm in the flexible tube from the carbon filter to the chiller and from the latter to the tap at the kitchen sink. This cooled water was used for providing drinking water and mouth care to ICU patients. The outbreak strains disappeared after removal of the water-cooler and the monthly incidence fell to <2% of ICU admissions.
CONCLUSION: This outbreak report highlights the risk from biofilms in devices that supply drinking water for ICU patients.