By Gary Evans, AHC Media Senior Staff Writer
An “insidious” under-the-radar outbreak of waterborne bacteria aerosolized by heater-cooler devices commonly used in cardiothoracic surgery is emerging as a clear and present danger to patient safety, a veteran epidemiologist recently warned at a meeting of infectious disease physicians in Atlanta.
“I use the term 'insidious' to describe this illness in terms of its very delayed onset of symptoms from the time of surgery and the very delayed time [from symptoms] to diagnosis,” Daniel Diekema, MD, chief of infectious diseases at the University of Iowa, said a May 20, 2016, meeting of the Society for Healthcare Epidemiology of America (SHEA). “I think this is probably the most challenging problem I have been presented as a hospital epidemiologist.”
Heater-cooler devices are used during cardiac surgical procedures to warm and cool a patient’s blood during cardiopulmonary bypass. The units have a closed circuit system to circulate water, but can create an aerosol that is vented into the immediate environs by an exhaust fan.
A heretofore obscure Nontuberculous Mycobacterium (NTM) named Mycobacterium chimaera — ubiquitous in soil and water but rarely pathogenic — appears to be perfectly adapted to take advantage of these conditions, collecting in water and biofilms before being aerosolized over the operating field and the open chest of the patient. Completing this dire equation is that the devices may be difficult to disinfect and continue using with confidence that a patient will not be exposed.
As this issue of Hospital Infection Control & Prevention went to press, the FDA had called a meeting of experts on the issue and issued a June 1, 2016, alert that some of the U.S. infections have been traced to the Stöckert 3T Heater-Cooler System by the Sorin Group in Germany.1 The company also submitted a letter to the FDA outlining measures it is taking to safeguard the equipment. (See related story in this issue.)
Moreover, discussions at the SHEA meeting indicate the 3T heater-coolers hold some 85% of the U.S. market and are used in hundreds of thousands of cardiothoracic surgeries annually. A massive recall, even if the FDA deemed that was necessary, appears to be out of the question. In pledging to redouble efforts to make the devices safer to use, the manufacturer made a cogent point to the FDA: “These products play an essential role in maintaining precise patient temperature during these cardiac surgeries and are a necessary part of the modern cardiac operating room infrastructure. No reasonable alternative is available.”2
Except one: an old school intervention that harkens back to the classic epidemiological decision John Snow took to end a cholera epidemic in 19th century London. He removed the pump handle to the contaminated water supply. Similarly, finding the units difficult or impossible to safely decontaminate, hospitals in the Netherlands and some in the U.S. have taken the radical step of physically removing the heating-cooling units from the OR, running the tubing and hookups needed for the patient through a wall that prevents aerosolization from the device fan to enter the sterile field. That’s what the University of Iowa did after identifying three patients with M. chimaera infections.
“In my view it is very unlikely that [these units] can be decontaminated,” Diekema said. “The experience by people to date has not been very encouraging. After most of the decontamination attempts, ultimately you can regrow the same organism from the unit. This is just my view — not the CDC’s, FDA’s or anyone else’s, necessarily — these units cannot be operated safely unless the air coming out of the exhaust is physically separated from the operating room.”
In addition to outbreaks in Europe,3,4 the CDC reported the largest outbreak to date in the U.S. at the recent Epidemic Intelligence Service meeting in Atlanta.5 A hospital in York, PA, has notified some 1,300 patients that had cardiac surgery over the last few years after discovering 10 patient infections with M. chimera, including six of whom died. These are slow-growing infections that may not appear for years, making case identification and a link to a heater-cooler device challenging.
In the York outbreak, investigators found that case patients had an NTM-positive culture during 2010-2015 obtained from a sterile body site 30 days to 3.5 years following cardiothoracic surgery. Cases had higher odds of undergoing major cardiac surgery involving cardiopulmonary bypass when body temperature was regulated by a heater-cooler unit. In particular, those undergoing bypass operations of more than two hours were at increased risk of infections, the CDC found. All three available case-patient isolates were positive for M. chimaera with indistinguishable pulsed-field gel electrophoresis patterns. The facility removed the heating- cooling units from service prior to CDC investigation, but environmental cultures, including water and air samples taken while the units functioned in a simulated environment, were also positive for M. chimaera.
High Degree of Difficulty
The problem — and there are many — is that the M. chimaera is exceedingly difficult to detect, treat, and eradicate from devices, shrugging off both antibiotics in humans and powerful disinfectants in machines. It subsequently emerges in post-surgical patients as a slow-growing but potentially fatal infection that may not become symptomatic for a year or more. Though there have been only an estimated 65 to 70 documented cases in the U.S. and Europe, it is a given that more cases are being missed because of the difficulty in detecting infections that appear far removed from the surgical exposure.
“The case-finding is very problematic with many patients receiving cardiopulmonary bypass away from home and all their follow-up care is local,” Diekema said. “The symptoms are very non-specific; they present months to years after the exposure. And exposure [during] cardiothoracic bypass has not normally — to this point — been considered a risk for this clinical syndrome. The risk mitigation issue is difficult as well, and I think we don’t know yet if these units can be decontaminated.”
The University of Iowa alerted some 1,500 surgical patients to seek evaluation after becoming aware in January that a patient who had an aortic valve replacement in 2012 had developed M. chimera infection that was not responding to treatment. Two other infected cardiac surgical patients were identified as Diekema and colleagues continue the look-back effort.
“Most disturbing is the crude mortality [in all cases] is well over 50%,” he said. “The story is not over yet — there are a lot of patients who are struggling with this and not doing well.”
Treatment is particularly difficult if the bacteria establish biofilms on prosthetic valves or other implanted materials to assist cardiothoracic function. Diekema underscored this point with a slide of a micro-valve ring removed from a patient in Europe still heavily contaminated with a biofilm despite a year of multidrug therapy.
“We have had similar experiences,” he said. “Our index case, who died just last weekend, had continuous mycobacteremia for well over a year despite multiple drug therapy. [There is] just an inability to eradicate this organism in the presence of prosthetic material.”
In a joint alert issued last year, the CDC and the FDA called for a number of measures, including using only sterile water in heater-cooler units. However, there are now questions whether that is enough to prevent infections because it is very difficult to disinfect the units after use no matter what quality of water is used. According to a European investigation,some of the units shipped before August 2014 may have been contaminated by the water used to test the devices at the manufacturing plant in Germany.
“These Sorin 3-T units very likely arrived pre-inoculated with M. chimera,” Diekema says. “The manufacturer changed their manufacturing process in August of 2014, so there may be reasons to believe that units manufactured before August of 2014 may have environmental mycobacterium in the unit at the time of delivery.”
Regardless, the larger question is whether units can be safety disinfected after continued use regardless of when they were made. An infectious disease physician from the Netherlands who was involved in some of the investigations in Europe told SHEA attendees during a question and answer session that hospitals in his country have similarly banned the units from the OR, so they are vented into a separate room.
Call to Action
As the potential scale of the problem becomes apparent, there was a sense of urgency and frustration at the SHEA meeting that the issue does not seem to be generating much traction and concern.
“The uptake on this has been a little frustratingly slow, I must say,” said Joseph Perz, PhD, an epidemiologist in the CDC’s Division of Healthcare Quality Promotion. “It is worrisome to me that ID docs and others are still not thinking NTM for these kinds of patients that have had these kinds of procedures.”
Perz said the CDC will continue to work with infectious disease groups and present findings at medical meetings to try and heighten awareness.
“It does seem to have emerged under the radar,” Diekema said. “I think that the relatively small number of cases, the newness of this disseminated presentation, and the fact that there are no simple solutions are some of the reasons for that. It would be one thing to say, ‘Recall these units,’ but then there would be no cardiac surgery. It’s frustrating when you are sitting in an exam room with a patient, as I have now on several occasions because we are managing these patients out of our ID clinic. They are asking us questions that we ought to be able to answer by now, but we can’t.”
There may also be a sense among some clinicians that the risk of infection is so low it is easily outweighed by the benefit of having the needed cardiac surgery.
“I normally have a good relationship with our cardiothoracic surgeons but the meeting to bring them in to even talk about this was most angry,” a clinician said at the SHEA meeting. “They didn’t want to hear about it, [saying] ‘Why are we are worrying about this? The risk is so low.’ So trying to engage them has been very difficult.”
Diekema had a suggestion that took the discussion back to its ethical crux: the patient on the operating table.
“You may want to give your surgeons the number of one of the thoracic surgeons in York, Pennsylvania,” he said. “They might take it a little more seriously.”
- FDA. Safety Alert for Human Medical Products. Stöckert 3T Heater-Cooler System by Sorin Group Deustchland GmbH: Safety Communication - Reports of Mycobacterium Chimaera Infections. June 1, 2016: http://1.usa.gov/1PfXSLX.
- LivaNova Inc. Letter: Docket No. FDA-2016-N-1126: Circulatory System Devices Panel of the Medical Devices Advisory Committee. May 19, 2016.
- Sax H, Bloemberg G, Hasse B et al. Prolonged Outbreak of Mycobacterium chimaera Infection After Open-Chest Heart Surgery. Clin Infect Dis. 2015 Jul 1;61(1):67-75. doi:10.1093/cid/civ198. Epub 2015 Mar 11.
- Haller S, Höller C, Jacobshagen A, et al. Contamination during production of heater-cooler units by Mycobacterium chimaera potential cause for invasive cardiovascular infections: results of an outbreak investigation in Germany, April 2015 to February 2016. Euro Surveill 2016;21(17): http://bit.ly/1Tgb70l.
- Lyman M, Grigg C, Kinsey CB, et al. Invasive Nontuberculous Mycobacteria Infections among Cardiothoracic Surgery Patients — Hospital A, Pennsylvania, 2010–2015. Epidemic Intelligence Service Conference. Atlanta: May 2-5 2016.