A study published today in the Annals of Internal Medicine suggests a multidrug-resistant bacteria outbreak that killed three hospital patients was likely linked to a commercial water purification system.
The study describes a Mycobacterium abscessus outbreak that occurred at Boston's Brigham and Women's Hospital from March 2017 to October 2017. The outbreak involved four cardiac surgery patients—two who had bloodstream infections, one with a left ventricular assist device driveline infection, and one with a sternal wound infection. All four patients were treated with multi-agent anti-mycobacterial regimens, and three died. Whole-genome sequencing of M abscessus isolates from the four patients suggested the infections were closely related.
Investigation into the source of the outbreak led researchers from Brigham and Women's and Harvard Medical School to obtain cultures from sinks and showers in each of the patient's rooms as well as two ice and water machines on the cardiac surgery intensive care unit and a step-down unit. The specimens from the ice machines were both positive for high concentrations of mycobacteria, as were two additional ice machines on the care patients' floor. Direct DNA extraction from ice and water machine samples found an exact match to a gene present in the outbreak samples.
Our cluster demonstrates the risk for unintended consequences associated with systems designed to improve hospital water.
Further investigation revealed that a commercial water purifier with charcoal filters and an ultraviolet irradiation unit that filtered water for one of the hospital's three inpatient towers was depleting chlorine levels, which may have allowed mycobacteria present in the municipal water system (which provides water to the hospital) to colonize that building's ice and water machines. The machines were removed, as was the water purification system, and no additional cases have since been reported.
"Our cluster demonstrates the risk for unintended consequences associated with systems designed to improve hospital water, the predilection of ice and water machines for microbial contamination and the risk this poses to patients, as well as the potential importance of augmenting hospitals' water management programs to monitor and prevent mycobacterial infections in addition to Legionella," the study authors wrote.