Public Health England (PHE) is working with the NHS, the Medicines and Healthcare Products Regulatory Agency (MHRA) and NHS England to investigate a small number of mycobacterial infections potentially associated with heater cooler units used during cardiopulmonary bypass for cardiac surgery.


After an alert from European colleagues at the end of February regarding Mycobacterium chimaera infections following cardiothoracic surgery, PHEhave conducted a look-back and have identified 13 cases of mycobacterial infections in people who had this type of surgery since 2007, 10 of which are Mycobacterium chimaera.

Small numbers of additional cases may continue to be identified over the coming months given the long incubation period in many of these cases. Although 7 of these individuals have subsequently died, it is too early to say if these deaths were from the infection or from other health conditions.

Mycobacterium chimaera is part of Mycobacterium avium complex, a group of mycobacteria which are found widely in the environment such as in soil and drinking water and are not harmful to the majority of healthy people. They can sometimes cause respiratory infections, or more serious infections in patients with weakened immune systems.

PHE is working closely with partner organisations, including clinicians,MHRA and NHS England to determine whether these infections are caused by the heater cooler units and to confirm the low risks to UK patients who have had or are undergoing cardiac surgery.

There are approximately 56,000 surgical procedures involving cardiopulmonary bypass performed on NHS patients across England each year.

Professor Nick Phin, deputy director of PHE’s National Infections Service, said:

Our investigation has so far identified a small number of people who have undergone cardiac surgery and developed mycobacterium infection; however the link between these cases and the heater cooler units has not yet been confirmed.

PHE and MHRA are working closely with the manufacturer to ensure updated and appropriate advice on cleaning and maintaining these machines is available for users. PHE has also supported infection prevention and control teams at cardiothoracic centres across the UK to undertake local risk assessments of their heater cooler units.

The risk of acquiring this infection is considered to be substantially smaller than the general risks of infection after cardiothoracic surgery and that in most cases, the risk of delaying surgery would outweigh this specific infection risk.

John Wilkinson, MHRA Director of Devices said:

We are aware of a small number of patients who have undergone cardiac surgery, where cardiopulmonary bypass has been used, and subsequently developed endocarditis and/or septicaemia associated with Mycobacterium chimaera.

We are working closely with PHE to investigate the issue and implications for UK hospitals and are in the process of issuing an Medical Device Alert advising of the action needed to minimise the risk of infection.