A water purification system installed in two ice makers at a Boston hospital was supposed to improve the taste and smell of water for patients on the operating floor, but an investigation found three deaths.
The water purification system accidentally removed chlorine from the city’s tap water, allowing bacteria normally found at low levels to thrive and form biofilms within the machine. This infected four vulnerable heart surgery patients who had been in bed for a long time, three of whom died from the infection.
The researchers detailed the case cluster and subsequent investigation in a study published Monday in the Annals of Internal Medicine.
“Our cluster demonstrates the risk of unintended consequences associated with systems designed to improve hospital water,” said Michael Krompus, a hospital worker and professor of population medicine at Harvard University. The researchers, led by
common source
It took quite a bit of investigation to identify the cluster and the culprit. His four cases occurred sporadically at Brigham and Women’s Hospital in Boston between March 2017 and October 2018. And it wasn’t immediately clear that they were linked.
Doctors became suspicious after documenting three cases in 2018. All of which were invasive. mycobacterium abscesus Infection. M. abscess Although infections are rare, they are known to be associated with medical care, called nosocomial infections, suggesting a common source of infection somewhere in the hospital. This prompted researchers to search hospital records dating back to 2015 for other potentially related cases. That’s when they identified a fourth case, which occurred in 2017.
Whole-genome sequencing of clinical isolates from the four identified cases revealed a near-perfect match between the cases. M. abscess Separate. The genomes of the bacterial isolates had only one to three different point mutations among them. Fewer than 20 suggest an epidemiological link. So researchers set out to find a common source of information.
Of the four cases, only three underwent surgery in the hospital, performed in different operating rooms, and were equipped with various cardiopulmonary bypass heating and cooling devices to help control the patient’s temperature during surgery. Only one patient required hemodialysis, which was ruled out as a common cause. Researchers also ruled out mechanical ventilation as a cause. The patients were all on the same cardiology floor of the hospital and each occupied multiple rooms during their stay, but he was the only one of the four patients shared by the two of them. .
The most obvious similarity in patient length of stay was the lengthening of all lengths of stay. The mean length of stay for similar patients on the cardiac surgery floor was just over 2 weeks for him, while the length of stay for four patients ranged from his 42 days to his 131 days. M. abscess has been identified. Also, the nurse anecdotally noted that the patient seemed to consume more ice than the others.
pure and deadly
M. abscess It is a water-loving bacterium known to be present at low levels in non-sterile tap water. So the researchers turned to the hospital’s water sources, examining sinks, showers, and floor ice makers and waterers.Two samples of the 14 sinks and showers on the floor had low levels of mycobacteria Contamination, 10-50 colony forming units per milliliter. However, the samples from the two ice makers and waterers were highly contaminated, with 2,000 to 8,000 colony forming units per milliliter. And from those samples, researchers were able to find gene sequences unique to that individual. M. abscess isolates that infected patients, strongly suggesting that this is a common source of infection.
Hospital records show that the machine had been maintained and cleaned according to the manufacturer’s instructions, but researchers noticed a visible bacterial biofilm on the internal components of the machine.
Surprised by this finding, the researchers began investigating sinks, showers, ice machines and water machines in other areas of the hospital, but found levels of bacterial contamination as high as two machines on the heart surgery floor. Nothing else was taken. This made more sense when they checked the chlorine levels.The chlorine levels were within acceptable limits for all but two machines.
Upon closer inspection, the researchers found that two machines were fitted with a commercial water purification system that included a 5.0-micron carbon filter (designed to improve taste and eliminate odors) and an ultraviolet disinfection unit. I noticed that Both carbon filters and UV light are known to reduce chlorine levels. Sampling from the input and output pipes confirmed that the purification system was stripping an acceptable input chlorine concentration of 2.5mg/L to 0mg/L at the output.
The ice machine was removed from service in October 2018. M. abscess After that, infection was confirmed.
“Our experience suggests potential dangers of well-meaning measures designed to improve water quality in health care facilities,” the researchers wrote in their study. We outlined various strategies that could help prevent such infections in the future, including switching to sterile or distilled water for care, regular sampling, and chlorine monitoring. We must be careful,” they wrote.
