Summary assessment of public health risk associated with Mycobacterium chimaera infections in patients exposed to heater-cooler devices in Canada
Table of contents
- Risk assessment
- Event summary
- Pathogen characteristics
- Heater-cooler devices
- Summary of literature
- Guidance for Canada
- Risk information
- Summary of risk assessment
- For more information
The public health risk of infections with Mycobacterium chimaera (M. chimaera), one type of non-tuberculous mycobacterium (NTM), in Canadian patients exposed to heater-cooler devices (HCD) used during cardiopulmonary bypass is currently not defined, but believed to be low to medium. The number of confirmed cases internationally is small compared to the number of patients exposed to heater-cooler devices while undergoing cardiopulmonary bypass surgery. However, given the long latency period, additional cases should be expected and our understanding of the exact risk is expected to improve as new information becomes available.
To date, only the Stöckert 3T heater-cooler devices manufactured by LivaNova PLC (formerly Sorin Group Deutschland GmbH) before September 2014 have been associated with M. chimaera infections.
In determining public health risk, many factors are considered in estimating the impact or severity of the disease, such as morbidity, mortality and complications, the burden of the disease, as well as its infectiousness, mode of transmission, period of communicability, length of incubation and asymptomatic period. Impact also depends on the availability of interventions that may contain, reduce or eliminate the transmission of the infectious agent, including treatment, prophylaxis and other control measures, and the health system's ability to accommodate a surge in demand.
While the magnitude of risk of exposure to M. chimaera is uncertain, the risk of delaying cardiac surgery is generally considered far greater than the risk posed by this infection, even when the infection risk has not been entirely mitigated. Transmission of NTM, such as M. chimaera, between persons is extremely rare and public health case management is not required.
This assessment is based on limited available evidence and is subject to review and change as new information becomes available.
Cases of M. chimaera infection associated with HCDs were first reported in 2014 in Europe and have since been reported internationally.Footnote 1
Tests conducted at the LivaNova manufacturing site in Germany (in 2014-2015) confirmed the presence of M. chimaera in samples taken in the pump assembly area and from newly manufactured HCDs. Genetic epidemiology studies have linked the isolates responsible for patient infections with the organisms recovered from Germany, suggesting the devices became contaminated from a point-source. Although NTM contamination of various HCD brands has been reported, only Sorin / LivaNova HCDs manufactured before September 2014 have been associated with M. chimaera-infected patients.
LivaNova PLC implemented a new disinfection and drying process (involving disinfection of new HCDs prior to shipment) at the production facility in mid-August 2014 to supplement the pre-existing cleaning and disinfection process. In addition, the company implemented monitoring for the presence of NTM at the manufacturing site. In October, 2016 LivaNova issued a field safety notice recommending, if feasible, any 3T HCDs suspected to be contaminated with NTM based on results of healthcare facility's testing or other information known by the hospital, be removed from service, and to contact the manufacturer to arrange for a deep-disinfection service prior to further use. There have been practical challenges identified with the implementation of this recommendation in some centres.
Health Canada issued a risk communication notice in October 2016 to notify healthcare facilities, providers and hospital staff responsible for operating and maintaining HCDs of important safety information on HCDs, the risk of NTM, and reiterating recommendations from the manufacturer.
The Montreal Heart Institute issued a Communication Notice on October 24, 2016, indicating that two patients were diagnosed with M. chimaera infection. These are the first confirmed cases linked to contaminated HCDs used during cardiopulmonary bypass surgery in Canada.
In January 2017 the Canadian Public Health Laboratory Network issued updated interim laboratory testing guidance for the detection of NTM infections in post-operative patients exposed to HCDs. The interim guidance was developed in collaboration with the Public Health Agency of Canada and its Infection Prevention and Control Expert Working Group.
M. chimaera is a slow growing NTM that was identified as a species of the Mycobacterium avium complex in 2004. This mycobacterium is widespread in nature and can be found in soil and water, including drinking water sources. These bacteria can occasionally cause infection in vulnerable patients, including those with compromised immune systems and underlying medical conditions. Transmission of NTM from person to person is extremely rare.
While M. chimaera infection has been associated with lung infections in vulnerable patients and those with underlying medical conditions, contaminated HCDs provide an unusual mechanism of potential infection by generating aerosols that can carry the organism during cardiopulmonary bypass surgery. This can deposit NTMs directly into the surgical site, which can lead to invasive disease that can be difficult to cure. Although the overall risk of infection from contaminated HCDs is considered low for patients that undergo cardiopulmonary bypass surgery, there are a number of challenges associated with diagnosis and treatment. Due to the nature of this slow growing bacterium, it can take months to years for the infection to evolve and for patients to manifest clinical illness. Symptoms of the infection can be non-specific, making its distinction from other, more common causes of infection, challenging. Infections of M. chimaera are difficult to treat and require prolonged, carefully monitored administration of a combination of antimicrobials. These antimicrobials have their own associated toxicities. Repeat surgery may be required and there is a high rate of treatment failure and fatal outcome associated with invasive infections.
HCDs are non-sterile devices used in operating rooms during procedures, including cardiopulmonary bypass surgery, where the patient's blood temperature needs to be heated or cooled. The HCD sits outside of the sterile field, but usually within the operating room.
The devices consist of water tanks that provide temperature-controlled water through closed water circuits to warming/cooling blankets or external heat exchangers. Patient temperature regulation is achieved by convection through the blankets or heat exchangers. Water from the closed circuit of heater-cooler devices does not come into contact with patients' blood or bodily fluids. However, multiple studies have confirmed the transmission of NTM via aerosolization of contaminated water in HCDs into the operating room, potentially exposing the patient during surgery.
Summary of literature
A number of challenges in management of the current M. chimaera outbreak have been identified in the literature. This includes limited laboratory capacity for identification of M. chimaera, delayed diagnosis of infection (due to the mycobacterium's long latency period and slow growth), prolonged therapy with multiple agents, poor response to antimycobacterial therapy, and uncertain reliability of HCD decontamination protocols.
In an effort to mitigate risk of exposure and infection, as well as to facilitate earlier diagnosis of infection, the following control measures have been described in the existing literature although there is limited data confirming that these measures prevent infection.
- Healthcare provider notification and education.
- Patient notification.
- Enhanced prospective surveillance.
- Identification of contaminated HCDs by microbiological testing.
- Replacement of contaminated HCDs including accessories, tubing, and connectors to prevent recontamination.
- Use of manufacturer's updated cleaning and disinfection protocols.
- Routine microbiological testing of HCDs in use.Footnote 2
- Engineering solutions to enable air separation between HCD exhaust air and operating room air.
- Improved engineering for alternative design to mitigate transmission of infection.
Guidance for Canada
Hospitals performing cardiopulmonary bypass surgery should identify and assess which HCDs are being used in their facility and increase awareness among health care professionals about the risk of infection associated with these devices.
For additional background information, key messages on this issue and action taken by Health Canada, refer to Health Canada's Risk Communication.
Health Canada encourages healthcare professionals to report any cases of patient infection thought to be associated with the use of devices. The Medical Devices Problem Report Form and Guidelines can be found on the Health Canada Web site.
For information describing clinical syndromes compatible with M. chimaera, as well as patient specimen and testing criteria, refer to the Canadian Public Health Laboratory Network's (CPHLN) Interim laboratory testing guidance for the detection of non-tuberculous Mycobacterium (NTM) infections in post-operative patients exposed to heater-cooler units.
For device testing recommendations, refer to the Canadian Public Health Laboratory Network (CPHLN) Device Testing Recommendations regarding Non-Tuberculous Mycobacteria (NTM) Contamination in Heater-Cooler Units.
For a summary of currently recommended risk mitigation measures from peer reviewed literature and additional background information, refer to the May 2017 (volume 43-5) issue of the Canada Communicable Disease Report.
- Public health issue
- Mycobacterium chimaera (M. chimaera) infection associated with heater-cooler devices (HCDs)
- Risk being assessed
- Public health risk associated with M. chimaera infection in patients exposed to HCDs used during cardiopulmonary bypass surgery
- Summary of issue
At least 77 cases of M. chimaera infection such as endocarditis, surgical site infection, and disseminated infection have been reported after open-chest heart surgery in Europe and the United States. To date, 3 cases have been publicly identified in Canada.
Only the Stöckert 3T HCD manufactured before September 2014 by LivaNova PLC (formerly Sorin Group Deutschland GmbH) has been associated with M. chimaera infections. Signs or symptoms of invasive M. chimaera infection may not occur for months or years after exposure. The infection is difficult to treat, as treatment is usually prolonged and involves use of multiple drugs. Severe infections have often required surgical interventions with high mortality rates.
- Likelihood of infection
- Impact of infection
- Low to Medium
- Risk assessment
- Low to Medium Risk
|Questions||Evidence from Summary of Literature||Quality of Evidence||Comments|
Are there patients at increased risk of infection?
Prosthetic material is not always a prerequisite for infection; a recently reported case occurred after coronary-artery bypass surgery with sternal wires as the only foreign material
Is M. chimaera highly infectious for exposed patients?
Are exposed patients more vulnerable to M. chimaera?
Cardiac surgery creates a breach in normal host defences
Is M. chimaera likely to cause significant morbidity in affected patients?
Patients who develop M. chimaera infection are more likely to have increased morbidity with surgical re-interventions and potential complications, prolonged hospital stays, and complications related to treatment side effects and/or treatment failure.
Is M. chimaera likely to cause significant mortality in affected patients?
There are limitations with data informing mortality rate as the study sizes are very small and co-morbidities have been reported. Reported mortality rates range from <28% to 50%. Studies reporting mortality rates at the higher end of the range are most often reporting on cases of severe infection. Timely detection of infection and initiation of therapy may decrease mortality rates.
Is there a significant number or proportion of patients affected among those exposed to HCDs?
Given the long latency period, additional cases should be expected
Are effective treatment measures available?
Patient outcomes are yet to be improved, especially for those with disseminated infection
Are effective control measures available?
The feasibility of implementing and optimizing current risk mitigation measures is yet to be determined
Summary of risk assessment
Likelihood of M. chimaera Infection
Given that the infection is not reportable in many countries, the true number of cases globally is likely unknown. However, the number of known cases world-wide is small compared to the very large number of patients undergoing cardiopulmonary bypass surgeries on an annual basis. This suggests that M. chimaera is not highly infectious for exposed patients despite their vulnerability due to the breach in normal host defences as a result of surgery. Although more cases are likely to be identified due to the long latency period, the current likelihood of infection is considered LOW.
Impact of M. chimaera Infection
The morbidity is important in affected patients. The high mortality rate is estimated based on limited known cases and the number of deaths directly attributable to the infection is currently unknown. Although control measures have been recommended, feasibility of implementation remains a challenge and not all measures can eliminate the risk of infection. Treatment options are available and can be pursued depending on individual patient characteristics such as co-morbidities. Early diagnosis and treatment with effective antimycobacterial therapy may help prevent the progression to severe illness. There may be significant adverse effects to treatment and possible treatment failure for disseminated infections. The impact is currently estimated as a range of LOW to MEDIUM.
Overall risk assessment
Taking into account the likelihood and impact of M. chimaera infection, and based on currently available data, the risk is considered LOW to MEDIUM.
|High||Medium risk||Medium risk||High risk||High risk|
|Medium||Low risk||Medium risk||Medium risk||High risk|
|Low||Low risk||Low risk||Medium risk||Medium risk|
|Very Low||Very low risk||Low risk||Low risk||Medium risk|
Figure 1 - Text equivalent
The risk matrix has four categories of risk for both likelihood of infection and impact including high, medium, low and very low. Likelihood of infection is displayed along the y axis starting with high followed by medium, low and very low. Impact is displayed along the x axis starting with very low on the left followed by low, medium and high moving to the right.
The 16 cells within the matrix identify level of risk based on likelihood and impact of infection combined.
The likelihood of infection for each category (high, medium, low and very low) combined with very low impact produces the following results in the risk matrix:
- High likelihood of infection combined with very low impact would be medium risk.
- Medium likelihood of infection combined with very low impact would be low risk.
- Low likelihood of infection combined with very low impact would be low risk.
- Very low likelihood of infection combined with very low impact would be very low risk.
The likelihood of infection for each category (high, medium, low and very low) combined with low impact produces the following results in the risk matrix:
- High likelihood of infection combined with low impact would be medium risk
- Medium likelihood of infection combined with low impact would be medium risk
- Low likelihood of infection combined with low impact would be low risk
- Very low likelihood of infection combined with low impact would be low risk
The likelihood of infection for each category (high, medium, low and very low) combined with medium impact produces the following results in the risk matrix:
- High likelihood of infection combined with medium impact would be high risk
- Medium likelihood of infection combined with medium impact would be medium risk
- Low likelihood of infection combined with medium impact would be medium risk
- Very low likelihood of infection combined with medium impact would be low risk
The likelihood of infection for each category (high, medium, low and very low) combined with high impact produces the following results in the risk matrix:
- High likelihood of infection combined with high impact would be high risk
- Medium likelihood of infection combined with high impact would be high risk
- Low likelihood of infection combined with high impact would be medium risk
- Very low likelihood of infection combined with high impact would be medium risk
Based on currently available data, the current likelihood of infection is considered low and impact is estimated as a range of low to medium. Within the image, the shaded boxes low risk to medium risk are formatted in bold to indicate an overall risk of low to medium.
Resources informing this document including peer reviewed publications and relevant international guidance are listed below.
- Achermann Y, Rossle M, Hoffmann M, Deggim V, Kuster S, Zimmermann DR, et al. Prosthetic Valve Endocarditis and Bloodstream Infection Due to Mycobacterium chimaera. J Clin Microbiol [Internet]. 2013 Jun;51(6):1769-1773.
- Antonation K, Patel S, Trumble Waddell J, Guillaume Poliquin P, Alexander DC, Hoang L, et al. Interim laboratory testing guidance for the detection of non-tuberculous Mycobacterium (NTM) infections in post-operative patients exposed to heater-cooler units. Can Comm Dis Rep [Internet]. 1-5-2017;43(1):25-28.
- Appenheimer AB, Diekema DJ, Berriel-Cass D, Crook T, Daley CL, Dobbie D, et al. Mycobacterium chimaera Outbreak Response: Experience From Four United States Healthcare Systems [Abstract] [Internet]. Open Forum Infect Dis. 2016;3[supp. 1]: 2392.
- Behr M, Jarand J, Marras TK. Canadian Tuberculosis Standards 7th edition, Chapter 11 - Nontuberculous Mycobacteria [Internet]. Ottawa (ON): Public Health Agency of Canada; 2014.
- Canadian Public Health Laboratory Network (CPHLN) Testing Working Group. Canadian Public Health Laboratory Network (CPHLN) Device Testing Recommendations regarding Non-Tuberculous Mycobacteria (NTM) Contamination in Heater-Cooler Units [Internet]. Ottawa (ON): Government of Canada; [updated 2017 Feb 9].
- Centers for Disease Control and Prevention. Non-tuberculous Mycobacterium (NTM) infections and heater-cooler devices interim practical guidance: Updated October 27, 2015. [Internet].
- Chand M, Lamagni T, Kranzer K, Hedge J, Moore G, Parks S, et al. Insidious Risk of Severe Mycobacterium chimaera Infection in Cardiac Surgery Patients. Clin Infect Dis. 2017;64(3):335-342.
- European Centre for Disease Prevention and Control (ECDC). Rapid Risk Assessment: Invasive cardiovascular infection by Mycobacterium chimaera associated with the 3T heater-cooler system used during open-heart surgery [Internet]. Stockholm (SE): ECDC; 11-18-2016.
- Food and Drug Administration, Medical Devices Advisory Committee. Nontuberculous Mycobacterium (NTM) Infections Associated with Heater-Cooler Devices (HCD) during Cardiothoracic Surgery [Internet]. Meeting of the Circulatory Devices Panel of the Medical Devices Advisory Committee. June 2-3, 2016.
- Food and Drug Administration. UPDATE: Mycobacterium chimaera Infections Associated with LivaNova PLC (formerly Sorin Group Deutschland GmbH) Stöckert 3T Heater-Cooler System: FDA Safety Communication [Internet]. Silver Spring (MD): [updated 2016 Oct 13].
- Galassi L, Donato R, Tortoli E, Burrini D, Santianni D, Dei R. Nontuberculous mycobacteria in hospital water systems: application of HPLC for identification of environmental mycobacteria. J Water Health [Internet]. 2003; Sep;1(3):133-139.
- Garvey MI, Ashford R, Bradley CW, Bradley CR, Martin TA, Walker J, et al. Decontamination of heater-cooler units associated with contamination by atypical mycobacteria. J Hosp Infect. 2016;93(3):229-234.
- Government of Canada. Heater-Cooler Devices - Risk of Nontuberculous Mycobacteria Infections [Internet]. October 21, 2016.
- Government of Canada. LivaNova Stöckert 3T Heater-Cooler Device - Risk of Mycobacterium chimaera Infections [Internet]. February 17, 2017.
- Haller S, Holler C, Jacobshagen A, Hamouda O, Abu SM, Monnet DL, 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 [Internet]. Apr 28, 2016;21(17).
- Institut de Cardiologie de Montréal. L'ICM avise ses patients opérés à coeur ouvert depuis 2012 d'un risque d'infection [Internet]. 10-24-2016.
- Kanamori H, Weber DJ, Rutala WA. Healthcare-Associated Mycobacterium chimaera Transmission and Infection Prevention Challenges: Role of Heater-Cooler Units as a Water Source in Cardiac Surgery. Clin Infect Dis. 2017;64(3):343-346.
- Kohler P, Kuster SP, Bloemberg G, Schulthess B, Frank M, Tanner FC, et al. Healthcare-associated prosthetic heart valve, aortic vascular graft, and disseminated Mycobacterium chimaera infections subsequent to open heart surgery. Eur Heart J. 7-17-2015;36(40):2745-2753.
- Lyman M, Grigg C, Kinsey CB, Keckler MS, Moulton-Meissner H, Noble-Wang J, et al. Invasive Nontuberculous Mycobacteria Infections among Cardiothoracic Surgery Patients - Hospital A, Pennsylvania, 2010-2015. 65th Annual Epidemic Intelligence Service (EIS) Conference, May 2-5, 2016. CDC, Atlanta, Georgia. P 94. Concurrent Session K2: Healthcare-Associated Outbreaks.
- Ogunremi T, Taylor G, Johnston L, Amaratunga K, Muller M, Coady A, et al. Mycobacterium chimaera infections in postoperative patients exposed to heater–cooler devices: An overview. Can Commun Dis Rep. 2017;43(5):107-13.
- Perkins KM, Lawsin A, Hasan NA, Strong M, Halpin AL, Rodger RR, et al. Notes from the Field: Mycobacterium chimaera Contamination of Heater-Cooler Devices Used in Cardiac Surgery - United States. MMWR Morb Mortal Wkly Rep [Internet]. 10-14-2016;65(40):1117-1118.
- Public Health Agency of Canada. Canadian Public Health Laboratory Network Interim Laboratory Testing Guidance For The Detection Of Non-Tuberculous Mycobacteria (NTM) Infections In Post Operative Patients Exposed To Heater Cooler Units [Internet]. [updated 2016 Nov 18].
- Public Health England. Mycobacterium chimaera: infections linked to heater cooler units [Internet]. 2017.
- Sax H, Bloemberg G, Hasse B, Sommerstein R, Kohler P, Achermann Y, et al. Prolonged Outbreak of Mycobacterium chimaera Infection After Open-Chest Heart Surgery. Clin Infect Dis [Internet]. 3-11-2015;61(1):67-75.
- Schreiber PW, Kuster SP, Hasse B, Bayard C, Ruegg C, Kohler P, et al. Reemergence of Mycobacterium chimaera in Heater-Cooler Units despite Intensified Cleaning and Disinfection Protocol. Emerg Infect Dis Oct 2016;22(10):1830-1833.
- Sommerstein R, Ruegg C, Kohler P, Bloemberg G, Kuster SP, Sax H. Transmission of Mycobacterium chimaera from Heater-Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System. Emerg Infect Dis [Internet]. Jun 2016;22(6):1008-1013.
- Sommerstein R, Schreiber PW, Diekema DJ, Edmond MB, Hasse B, Marschall J, et al. Mycobacterium chimaera Outbreak Associated With Heater-Cooler Devices: Piecing the Puzzle Together. Infect Control Hosp Epidemiol. 2017;38(1):103-108.
- Sorin Group. 3T - USA [Internet]. 2016.
- Struelens MJ, Plachouras D. Mycobacterium chimaera infections associated with heater-cooler units (HCU): closing another loophole in patient safety. Euro Surveill [Internet]. 11-17-2016;21(46):1-3.
- Svensson E, Jensen ET, Rasmussen EM, Folkvardsen DB, Norman A, Lillebaek T. Mycobacterium chimaera in Heater-Cooler Units in Denmark Related to Isolates from the United States and United Kingdom. Emerg Infect Dis. 2017;23(3):507-509.
- Williamson D, Howden B, Stinear T. Mycobacterium chimaera Spread from Heating and Cooling Units in Heart Surgery. N Engl J Med. 2-9-2017;376(6):600-602.
For more information
- Canadian Public Health Laboratory Network (CPHLN) Device Testing Recommendations regarding Non-Tuberculous Mycobacteria (NTM) Contamination in Heater Cooler Units
- Canadian Public Health Laboratory Network Interim Laboratory Testing Guidance For The Detection Of Non-Tuberculous Mycobacteria (NTM) Infections In Post Operative Patients Exposed To Heater Cooler Units
- Footnote 1
Cases of M. chimaera have been reported in Australia, Canada, France, Germany, Hong Kong Special Administrative Region, Ireland, the Netherlands, Spain, Switzerland, the United Kingdom and the United States.
- Footnote 2
This is not widely adopted due to technical challenges identified with sampling and testing.
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