Bacteria in water purifier potentially to blame for three deaths at major hospital

A commercial water purifier was possibly responsible for infections among four patients undergoing cardiac surgery at Brigham and Women’s Hospital, three of whom died, according to a study published in Annals of Internal Medicine.

Michael Klompas, MD, MPH, an associate professor at Harvard Medical School and infectious disease physician at Brigham and Women’s Hospital, wrote that health care-associated outbreaks of Mycobacterium abscessus — described as “a rare but well-described nosocomial pathogen” — have previously been attributed to “contaminated aqueous systems,” like ice and water machines, humidifiers, hospital plumbing systems, heater-cooler devices used for patients undergoing cardiac bypass, medications and disinfectants.

In June 2018, the infection control department of Brigham and Women’s Hospital was alerted to the fact that several patients who underwent cardiac surgery had developed invasive M. abscessus subsp. abscessus infections, which can cause infections of the bloodstream, lung, skin and soft tissue, especially for patients with weak immune systems.

The researchers conducted a descriptive study to better understand the cluster of infections. They sought commonalities among cases, like heater-cooler devices or operating rooms used, the hospital floor and rooms and exposure to specific machines. The researchers also obtained water samples from all of the rooms the patients had occupied and from the two water and ice machines on the cardiac surgery floor.

All four patients were “aggressively treated with multiagent antimycobacterial regimens,” but three had died, Klompas and colleagues wrote.

The researchers found that all the patients had stayed on the same hospital floor but there were no other common factors. When investigating the ice and water machines, they noted heavy mycobacterial growth on the cluster unit, but not in any other location.

With whole-genome sequencing, they then found a genetically identical element in the water and ice machines that were on the hospital floor the infected patients were on. The water leading to these machines was going through a water purifier that had charcoal filters and ultraviolet irradiation, which the researchers found to be diminishing the water’s chlorine levels, potentially facilitating the mycobacterial colonization of the machines.

Once high-risk patients were switched to sterile and distilled water, water machine maintenance was intensified and the purification system decommissioned, there were no further cases.

“The commercial water unit was installed to improve the taste of patients' water and to minimize odors but may have had the unintended consequence of facilitating microbial colonization and proliferation,” the researchers wrote. “This echoes the experience of other hospitals that have reported that well-intentioned measures to improve water management (for example, increasing water recirculation in order to reduce energy use for heating) may inadvertently increase infection risk for patients by depleting chlorine and facilitating microbial proliferation.”

Klompas and colleagues concluded that their investigation “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.” It also indicates the importance of supporting water management programs to monitor and prevent mycobacterial infections in hospitals.

“More broadly, our experience reaffirms the potential risks associated with tap water and ice in the care of vulnerable patients and the potential value of emerging initiatives to minimize susceptible patients' exposure to tap water and ice during routine care,” they wrote.