Cluster in Cardiac Surgery Patients Potentially Attributable to a Commercial Water Purification System.

Background: Nontuberculous mycobacteria are water-avid pathogens that are associated with nosocomial infections.

Objective: To describe the analysis and mitigation of a cluster of infections in cardiac surgery patients.

Design: Descriptive study.

Setting: Brigham and Women's Hospital, Boston, Massachusetts.

Participants: Four cardiac surgery patients.

Intervention: Commonalities among cases were sought, potential sources were cultured, patient and environmental specimens were sequenced, and possible sources were abated.

Measurements: Description of the cluster, investigation, and mitigation.

Results: Whole-genome sequencing confirmed homology among clinical isolates. Patients were admitted during different periods to different rooms but on the same floor. There were no common operating rooms, ventilators, heater-cooler devices, or dialysis machines. Environmental cultures were notable for heavy mycobacterial growth in ice and water machines on the cluster unit but little or no growth in ice and water machines in the hospital's other 2 inpatient towers or in shower and sink faucet water in any of the hospital's 3 inpatient towers. Whole-genome sequencing confirmed the presence of a genetically identical element in ice and water machine and patient specimens. Investigation of the plumbing system revealed a commercial water purifier with charcoal filters and an ultraviolet irradiation unit leading to the ice and water machines in the cluster tower but not the hospital's other inpatient towers. Chlorine was present at normal levels in municipal source water but was undetectable downstream from the purification unit. There were no further cases after high-risk patients were switched to sterile and distilled water, ice and water machine maintenance was intensified, and the commercial purification system was decommissioned.

Limitation: Transmission pathways were not clearly characterized.

Conclusion: Well-intentioned efforts to modify water management systems may inadvertently increase infection risk for vulnerable patients.

Primary Funding Source: National Institutes of Health.