A seventh patient, a man aged in his 80's who had heart valve replacement surgery at Prince of Wales Hospital in 2015 has been diagnosed with Mycobacterium chimaera infection. The onset of symptoms related to his infection started at least 3 years ago. Genome sequencing evidence from his clinical samples strongly links him to 6 other cases diagnosed following surgery at Prince of Wales Hospital, and to the worldwide outbreak of M. chimaera infection following exposure to the rare bacteria during open heart surgery.
Because M. chimaera are slow-growing bacteria, patients need to remain alert for symptoms of infection after their open heart surgery involving the affected equipment, particularly if surgery included implants, such as heart valves, and seek medical advice straight away if symptoms develop. To date, the longest time after surgery for an infection to be identified is 12 years, reported in a patient from Italy.
As this is an international problem, patients who had cardiac surgery in other states or territories, or overseas could also have been exposed.
There is a risk that certain heater-cooler devices used in open-heart cardiac surgery may have been contaminated with a rare bacterium called Mycobacterium chimaera (or M. chimaera), and that exposure of patients to these units during cardiac surgery may lead to infections that can appear months to years after the surgery.
In 2015, a cluster of cardiac surgery patients with M. chimaera were reported from Switzerland (2). Related cases have subsequently been reported from Germany, the Netherlands, the United Kingdom, the United States and Australia.
M. chimaera infections in cardiac surgery patients have been associated with exposure to a particular heater-cooler device - the Stöckert 3T made by Sorin (now known as LivaNova). These devices, which are widely used around the world, are thought to have been contaminated during manufacture up until September 2014.
M. chimaera are slow-growing bacteria and infections have been diagnosed from months to up to twelve years after open-heart surgery involving the implicated heater-cooler devices.
The Therapeutic Goods Administration (TGA) has provided alertson this issue and the Australian Commission on Safety and Quality in Health Care (ACSQHC) also issued new National Infection Control Guidance relating to heater-cooler devices , in March 2020.
The overall risk to individual patients is thought to be very low. There is a higher risk for patients who had prosthetic implants (such as heart valve replacements) during their cardiac surgery compared to those who did not receive implants.
In August 2016, NSW Health responded to international reports of infection in patients due to M. chimaera bacteria associated with open heart surgery machines by:
South-Eastern Sydney Local Health District contacted people who had open heart surgery at Prince of Wales and St George Hospitals during the potential risk periods. Reminder letters continue to be sent to these patients. NSW Health recommended that private hospitals provide similar reminders to their patients. The Sydney Children's Hospital Network provided information to parents of children who had open heart surgery at the affected hospitals through their regular specialist follow-ups.
Seven NSW residents who had open heart surgery at Prince of Wales Hospital in 2015 have been confirmed to have developed M. chimaera infections. Unfortunately, two of these people have subsequently died.
Information on cases in other States and Territories is available via the TGA Infections associated with heater-cooler devices alert.
Unfortunately, there is no test to tell if a patient has been exposed to the bacteria before symptoms of the infection develop.
Patients should talk to their specialist or general practitioner for further information.
Sterile site samples from patients with prosthetic valve endocarditis, mediastinitis, infective endocarditis, graft infection, sternal wound infection or other cardiac or other transplanted organ infection three or more months post-cardiothoracic surgery (highest risk is valve surgery) should be cultured for Mycobacteria in addition to standard bacterial culture.
Alternatively, infected tissue samples, after the assessment of M. chimaera infection risk, can be subjected to panbacterial 16S rDNA PCR which is available at the ICPMR-Pathology West.