A common feature in hemodialysis units – recessed wall boxes to hook up water and other lines – can become a reservoir for pathogens if not subjected to routine cleaning and infection control measures, a Centers for Disease Control and Prevention (CDC) investigator reports.
Shannon A. Novosad, MD, an officer in the CDC epidemic intelligence service recently reported the outbreak in Atlanta at the annual EIS meeting.1
Approximately 29,000 bloodstream infections (BSIs) occur in hemodialysis patients annually, but gram-negative bacteria are an uncommon cause. In November 2016, Novosad and colleagues investigated an unusually large cluster of gram-negative BSIs at three outpatient hemodialysis facilities (A, B, and C) owned by the same company.
They conducted a case-control investigation, infection control review, and collected environmental samples. A total of 58 cases occurred, with 33 infections in facility A, 19 in B, and 6 in facility C. One patient died during the 30-day follow-up period.
“They had a median length of stay of almost 8 days so they did require significant medical care,” Novosad tells Hospital Infection Control & Prevention.
The predominant organisms included two opportunist water bugs, Serratia marcescens (21 cases) and Pseudomonas aeruginosa (12 cases). Cases were more likely than controls to use a central venous catheter (CVC) for dialysis (85% vs. 13%).
“Many if not all of them required the catheters to be removed or replaced and they were on antibiotics,” Novosad says.
Facility staff reported pooling of water in recessed wall boxes that house connections between dialysis machines and facility water. Environmental samples revealed S. marcescens and P. aeruginosa in dialysis treatment areas, including the wall boxes. S. marcescens from a wall box at Facility C was indistinguishable by molecular epidemiology from a case-patient isolate. The CDC investigators identified multiple opportunities for healthcare workers’ hands to contaminate CVCs with water from the wall box connections. Wall boxes were identified as a unique source of water contamination in this multi-facility BSI outbreak that particularly affected patients with CVCs. The company is working with public health officials to remediate wall boxes and improve infection control practices.
“[Wall boxes] are actually very common,” she says. “Basically every dialysis station in these clinics and dialysis units – the ones we were in had 30 to 40 stations – had one of these individual wall boxes. For each dialysis session the machine has to be hooked up to this wall box. Different things come from the wall box into the dialysis machine. The water that has been purified as well as the bicarbonate and acid that is required for the dialysis. And in addition there is a drain line that leaves the machine and goes back to the wall box and that’s for the waste.”
The latter was the likely culprit, as some of the waste water bubbled up in the basin instead of being completely drained off.
“We think it is not the water itself that goes into the machine, but the water that comes out of the waste line,” she says. “[There may have been] biofilms forming on drain lines that were kind of bubbling back up or clogging.
That created enough of a reservoir for healthcare worker to contaminate hands and dialysis machine surfaces and equipment.
“We did a lot of interviews with staff at these facilities because these infections were going on over an extended time period,” she says. “We were really able to talk to them about how practices had changed and what they noticed about the wall boxes over time. There practices at the time – they weren’t necessarily performing hand hygiene whenever they touched the wall boxes. The [boxes] were not necessarily perceived as a contaminated or dirty area. A lot of times they would touch the wall box and then either go directly back to the patient, or manipulate their dialysis machine, adjust settings or touch the buttons. We think this back and forth – getting [the contaminated water] on your hands and either directly transferring it to patient at that time or coming in into contact with the dialysis station -- were the primary means by which this was happening.”
The outbreak subsided with education and observation, including auditing to make sure that the techs and nurses the touched the wall boxes were practicing hand hygiene. Daily cleaning and disinfection of the wall boxes became routine.
“We helped them formalize this process during the field investigation,” she says. “Then we went back with another CDC team and visited more facilities in the area and looked at how wall boxes were being cleaned. We are working with facilities, administrators and the company as a whole right now looking at a protocol or process to use for disinfection. Not just of the wall boxes but of the dialysis stations in general.”
Anomaly or Common Threat?
The CDC is still trying to determine if the outbreak represents some kind of anomaly or whether water boxes could be a source of dialysis infections that are probably underreported. For now, err on the side of suspicion that wall boxes could be involved if you start seeing dialysis infections.
“We are in the process of working with the dialysis company in this situation to really try to get this message out because every outpatient dialysis facility has these wall boxes,” she says. “While the configuration can vary, we think this could definitely be a problem in more places. It’s definitely something we are looking into.”
As with other outbreaks, the sheer number of cases may have revealed a problem that is also occurring in intermittent, ongoing infections.
“We think in this case we were able to make this association, and it may not have been noticed [except] for the large number of infections,” Novosad says. “It could be something that is occurring in much smaller numbers in other places, and it is still under the radar for a lot of people.”
- Novosad SA, Lake J, Soda E, et al. Unusual Source of Gram-Negative Bloodstream Infections in Hemodialysis Patients — Illinois and Missouri, 2015-2016. CDC EIS Conference. Atlanta, April 24-27, 2017.