The link between M. chimaera and heater cooler units grows stronger

A new paper in the Journal of Hospital Infection from Germany confirms the work of Hugo Sax and colleagues in Switzerland on the aerosolization of M. chimaera by heater cooler units. These investigators cultured M. chimaera from the water tanks of 4 Sorin heater cooler units, and were able to culture the organism from the air in the operating room only when the units were turned on. They were also able to culture non-fermenters from the air up to 10 feet from the heater cooler units when the units were turned on, but not when they were turned off. Importantly, the investigators were not able to culture M. chimaera from the hospital's water supply. And the authors note that whole genome sequencing of clinical and environmental isolates from the Netherlands and Germany suggests the possibility that the heater cooler units are intrinsically contaminated (i.e., this is a point source outbreak).

Lastly, the authors state that "only strict separation of the heater cooler unit from the operating room appears to enhance patient safety." We agree and that is the mitigation strategy that we have used at the University of Iowa. Below are photographs of our engineers' solution, a 6 x 6 inch Corian portal through the wall of the operating room, so that the heater cooler units are housed outside of the OR. The door is light weight and closes fully when the heater cooler device is not needed, and partially when the heater cooler hoses are extending through the wall. Positive pressure in the OR is maintained when the portal is in use.

Dan and I have spoken with a number of physicians from across the country, and we are now aware of 18 M. chimaera infections in patients who have undergone cardiopulmonary bypass. All of these patients, with the possible exception of 1 patient, had a prosthetic valve or vascular implant placed. So patients with implants are most important if a look back needs to be performed for case finding.

More on NTM as healthcare-associated pathogens

Since we began blogging about the link between heater-cooler units (HCUs) and M. chimaera infection, we’ve been contacted by people from across the country who are struggling with this problem. We’ve also heard from some nontuberculous mycobacteria (NTM) experts. Today we received an email from Dr. Joseph Falkinham, whose lab focuses on several aspects of the epidemiology, ecology, and genetics of NTM. He recently gave a webinar on NTM as an emerging waterborne hospital pathogen, providing excellent background information. You can download it here on his laboratory website, and I’ve also included the content below.

   NTM Webinar Dec 10

NTM aren’t on anyone’s short list of common healthcare-associated pathogens--but with their combination of ubiquity and low virulence, they’ll sneak up on you.

M. chimaera transmission in the OR: Progress from Switzerland

Hugo Sax and his colleagues first reported the link between heater-cooler units (HCUs) and an outbreak of invasive Mycobacterium chimaera infections, and today they published a follow up investigation that strongly supports their hypothesis regarding mode of transmission.

I encourage you to read the article for yourself, but it describes a set of experiments using smoke dispersal and particle counts to demonstrate that the HCU tested (Sorin Model 3T) both dispersed smoke and increased particle counts over the surgical field in a OR with ultraclean airflow ventilation (also known as laminar flow). As would be expected, the dispersal of smoke and particles was greatest when the unit exhaust was oriented toward the surgical field, but higher particle counts were noted even when the exhaust was oriented away. Finally, settle plates were used to show that M. chimaera could be isolated up to 5 meters away from a contaminated HCU while it was in operation (this experiment was performed in a non-ventilated test room, so in essence determined how far the aerosols carried when no air currents were being generated (other than by the HCU itself). 

The video below shows how smoke dispersal through the HCU was carried by the OR ventilation system to directly over the surgical field (scary!). 

The authors point out that airflow systems designed to keep OR air clean may fail to protect against, or paradoxically contribute to, the dispersal of HCU exhaust over the surgical field. While I find this an interesting explanation for why some patients may be at higher risk for exposure and infection than others, the main story here is still that there is a device in the OR that produces a microbial aerosol:

“Heater–cooler units are stand-alone devices that contain a tank that holds filtered tap water, which serves as transfer fluid to control the temperature of patient blood and cardioplegia solution……The tank features filling and overflow tubes, heating and cooling coils, probes, and stirring devices. It is not airtight [emphasis mine]. The space beneath the tank holds a radiator to dissipate superfluous heat produced through water cooling. The efficacy of this radiator is increased by a fan that ensures a constant airflow through ventilation grid openings on either side of the heater–cooler unit housing.”

In short, this HCU seems designed to produce contaminated aerosols once it becomes colonized. Thus the only two options are to get the units out of the OR, or find a way to keep them clean. On this point, there is another key tidbit from this article: 

“…M. chimaera has regrown in some of the monthly water cultures from most factory-new heater–cooler units delivered in January 2014 after 1 year of operation on a daily water-change with filtered tap water scheme…”

This is consistent with what we’ve learned from others dealing with this issue: there seems to be no reliable way to keep these units free of contamination, or to decontaminate them once they are contaminated. 

Thus the most important sentence in this article is the last one: 

“…all heater–cooler units should be reliably separated from air that can gain access to sterile areas and instruments...”

How to accomplish this is the current challenge: we took the approach of removing the units entirely from the OR, while the authors report that “their exhaust air is now captured by a secondary housing and reliably channeled to the operating room exhaust.” 

Until a better-designed (i.e. safe) HCU is widely available, hospitals are in dire need of guidance about how to eliminate this insidious risk to their patients.

M. chimaera update

Big Sky, Montana

Dan and I are at the Infectious Diseases Winter Course in Big Sky, Montana. I'm writing this blog post sitting by the fire while he's out hitting the slopes. This morning, Dan gave a talk on the M. chimaera outbreak associated with heater cooler units in an effort to raise awareness among ID clinicians.

While we continue to work on case finding at the University of Iowa, we continue to receive calls from physicians across the country asking for advice. One of the major problems is the paucity of data to guide recommendations for the best approach to outbreak investigation.

We need CDC and FDA to expedite the needed work to answer many questions. At this point, there is no published descriptive epidemiology of the cases in the United States. There's still no information on molecular typing of the patient and environmental isolates to sort out whether this a point source outbreak with contamination occurring during the manufacturing process of the heater cooler devices. Every hospital working on this issue is struggling alone in the dark, while it's becoming increasingly clear that this is an expanding outbreak.

Today we learned that a class action lawsuit has been filed against Sorin, the manufacturer of the implicated devices.

We'll post more on this topic as it unfolds.

Greyness

Applies to all writing - even scientific  - maybe especially scientific

SHEA Spring Meetings 2007, 2011, 2015 and Beyond?

A decade ago, I was a young associate professor of Epidemiology at the University of Maryland School of Medicine in Baltimore. One afternoon I received a call from Dr. Trish Perl, then President of SHEA and crosstown colleague. Two years earlier, she and I had met when we assisted with the infection control of Bob, an Atlantic Bottlenose Dolphin at the National Aquarium, who had been diagnosed with Mycobacterium abscessus pneumonia. She was not calling about marine mammals this time, but rather was asking me to serve on the 2007 SHEA Annual Meeting Planning Committee, as the local "Baltimore" representative. It was an amazing experience. For one, it was when I met future colleague, friend and co-blogger Dan Diekema and other mentors and colleagues - see the 2007 AMPC roster below.

Over the years I've been asked to serve on many other meeting committees including the last old format SHEA Scientific Meeting in Dallas (2011) and the first combined meeting, IDWeek 2012. As 2016 represents my last year on the SHEA Program Planning Committee, I've been looking back over the old committee rosters and reminiscing. What struck me most, besides the amazing colleagues I've crossed paths with, is the overwhelming presence of MDs, specifically ID-trained, on the committees. Looking at the rosters from 2007 (above) and 2011 (right) and excluding SHEA staff, 94% were ID physicians over both years.

The preponderance of ID physicians is not surprising, given that SHEA was founded by ID physicians and our board of directors roster is made up of ID physicians. However, the science and practice of infection prevention and stewardship is evolving into a broader multidisciplinary effort. We now frequently collaborate and learn from a variety of well-trained scientists and clinicians including medical sociologists, medical anthropologists, epidemiologists, biostatisticians, human-factors engineers, infection preventionists, general internists, MBAs, health economists, pharmacists, microbiologists and health psychologists among others.

When faced with the daunting task of walking in the footsteps of prior co-chairs, Lindsay Nicolle, Scott Fridkin, Charlie Huskins and Dan, we recognized that we had an opportunity to broaden the appeal of the conference and strive towards a truly multidisciplinary program. So in 2015, working with the SHEA board and staff, Susan Huang and I convened a Program Planning Committee (figure below) with 42% of its members trained in fields other than infectious diseases. 

This is not to imply that ~40% is the correct balance. Maybe it should be closer to the 15% of 2016. Perhaps future spring meetings will have an implementation focus and over 50% of the planning committee could be experts outside of infectious diseases and other years the focus could be diagnostics and the committee could be loaded with microbiologists. 

The important thing is that we realize that clinical and scientifically, SHEA and our meeting should not be defined by what we were (ID physicians) and what we are not (APIC), they should be defined by what we hope to achieve. And if we truly hope to prevent healthcare-associated infections and the emergence of antimicrobial-resistant pathogens, we need more than ID physicians. Plus, I think it will be a lot of fun!

What happens when you flush a toilet?

Many of you know that I'm not a fan of the uncovered toilet in hospital rooms or anywhere for that matter. Over at Fast Company, they have an amazing post with high-speed video (included above) from Lydia Bourguiba, an MIT professor who studies fluid dynamics and disease. The focus of this 1000-2000 frame per second video is the small particle or aerosol transmission that occurs after a toilet is flushed, think C. difficile. Enjoy! Oh, and sorry to ruin your breakfast or lunch.