Mycobacterium chimaera in heater cooler units

ACT Health is alerting the community to an issue involving a specific brand of heater-cooler unit commonly used worldwide in open-heart surgery has been linked to a small number of cases of infection with an uncommon environmental bacterium called Mycobacterium chimaera.  The heater-cooler units are thought to have been contaminated with the bacteria during the manufacturing process in Europe.

These devices have been used at the Canberra Hospital and at the National Capital Private Hospital.

The estimated risk to patients of infection with this bacterium is very low. Public Health England estimates the risk to be 1 per 10,000 patients undergoing valve replacement surgery. Internationally, nearly all infections have been in those who have had valve replacements or in those where graft material has been inserted. Patients who have only had coronary artery surgery are at a much lower risk. There has only been one patient diagnosed with this infection in Australia.

Mycobacterium. chimaera is a slow growing bacterium, making it difficult to diagnose in people with infection.  Symptoms may only develop months to years after the person’s cardiac surgery, however treatment is available.

Symptoms may include:

  • Fatigue
  • Night sweats
  • Unexplained weight loss
  • Unexplained fever
  • Muscle or joint pain
  • Persistent cough
  • Difficulty breathing
  • Redness, heat or pus at the surgical site

If people who have had open-heart surgery in the ACT during the last five years have experienced any of these symptoms and are concerned, you are recommended to make an appointment with your general practitioner for review.

Summary of the issue:

  • These devices, which are widely used around the world including Australia, are thought to have been contaminated during manufacture.

  • At least 60 patients worldwide have been identified with M. chimaera infections after cardiac surgery, including one case in Australia. There are no known cases in the ACT.

  • Infection of cardiac surgery patients with M. chimaera associated with a specific brand of heater-cooler unit was first advised by Therapeutic Goods Administration (TGA) in 2015.

  • The TGA provided a further update on this issue in August 2016, which noted testing and cleaning instructions and the Australian Commission on Safety and Quality in Health Care (ACSQHC) issued new National Infection Control Guidance relating to heater-cooler devices in September 2016.

  • With the updated directions issued from TGA and the ACSQHC, further testing on the units here in the ACT was undertaken. Following this testing, all units have been replaced with new alternatives, providing the latest technology for patients requiring this kind of life-saving surgery.

  • The risk of M. chimaera infection to an individual patient is very low. It is estimated that approximately 1 in every 10, 000 open heart valve replacement cardiac surgeries can be affected.

Patient Information

What is the issue?

It has recently been recognised that a specific brand of medical device used in open-heart surgery, known as a heater-cooler unit, has the potential to be contaminated with an uncommon environmental bacterium called Mycobacterium chimaera (M. chimaera), which grows in the unit’s water tank.

The water and the heater-cooler unit itself never comes into contact with the patient’s blood or body fluids.  M. chimaera can become airborne from the heater-cooler device, and can make contact with a patient’s wound during open heart surgery, potentially resulting in infection. The risk of infection however is very low.

What are heater-cooler units?

Heater-cooler units are life-saving medical devices used during open-heart surgery. These units are used around the world, including in Australian hospitals.

Heater-cooler units enable doctors to regulate the temperature of the patient’s blood during the surgery. The machine uses water to warm or cool the blood as it is circulated outside of the patient’s body.  See http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/CardiovascularDevices/Heater-CoolerDevices/  for more details.

 What is Mycobacterium chimaera? 

Mycobacterium chimaera (known as M. chimaera) is one of a group of bacteria called Non-Tuberculous Mycobacterium (NTM) which is commonly found in the environment, including in soil and water.

M. chimaera very rarely causes infections in healthy people. Patients with weakened immune systems due to other medical conditions or those with implanted medical devices, such artificial heart values, are more susceptible to infection if exposed to this bacterium.

M. chimaera is a slow growing bacterium that can be difficult to diagnose in patients as symptoms may only develop months to years after the patient’s cardiac surgery.

M. chimaera infection cannot be spread from person-to-person.

Who is at risk?

Patients who had open-heart surgery from November 2011 to August 2016 at National Capital Private Hospital or from July 2014 to November 2016 at Canberra Hospital may be at risk.

What are the symptoms of Mycobacterium chimaera infections?

  • Fatigue
  • Night sweats
  • Unexplained weight loss
  • Unexplained fever
  • Muscle or joint pain
  • Persistent cough
  • Difficulty breathing
  • Redness, heat or pus at the surgical site

What should I do if I am at risk?

If patients who had open-heart surgery between the dates above have experienced any of the symptoms listed and are concerned it is recommended they make an appointment with a General Practitioner for review.

Patients should continue to look for symptoms of unexplained infection as infection may only present months to years after the cardiac surgery.

Download (PDF fact sheet)

Clinician Information

For patients who have undergone open-heart surgery, please consider:

  • As only a small number of cases have been identified globally to date, the risk to individual patients of M. chimaera infections is thought to be very low.
  • Infection with NTM should be considered in patients with surgical site infection who have had cardiac surgery, particularly if conventional cultures are negative, if infections are not responding as expected, and those with unusual presentations.
  • The diagnosis of NTM infections may require specialised microbiological techniques; consultation with an infectious diseases physician or clinical microbiologist is recommended.

M. chimaera is slow-growing and patients may not experience symptoms for months or even years after surgery.  Patients have presented with a variety of clinical manifestations. Common examples include endocarditis, surgical site infection or abscess and bacteremia. Other clinical manifestations have included hepatitis, renal insufficiency, splenomegaly, pancytopenia and osteomyelitis.

Patients have also presented with granulomatous disease which can imitate sarcoidosis.

Symptoms of Mycobacterium chimaera infection may include:

  • Fatigue
  • Night sweats
  • Unexplained weight loss
  • Unexplained fever
  • Muscle or joint pain
  • Persistent cough
  • Difficulty breathing
  • Redness, heat or pus at the surgical site

If you have a clinical question pertaining to one of your patients, or if you have a symptomatic patient who requires additional evaluation for potential M. chimaera infection, please contact the patient’s cardiologist/cardiothoracic surgeon or call the Canberra Hospital on 6244 2105 and speak to the on call Infectious Diseases Physician.

Further information