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A Queensland infectious diseases expert has warned more open-heart surgery patients could be diagnosed with a rare bacterial infection stemming from contaminated heater-cooler units.

Dr Paul Griffin from the has diagnosed and treated a 68-year-old woman with Mycobacterium chimaera 13 months after she had open cardiothoracic surgery.

He said the case demonstrated the challenges of identifying the infection.

“Symptoms can be variable and might not show until months or years after exposure because this infection comes on very slowly,” he said.

“It was clear our patient had something significant and it was very frustrating that a raft of blood tests, scans and cultures came back negative.

“It wasn’t until a bone marrow biopsy was done that we were able to culture the organisms to prove it was this disease from the heater-cooler unit.

“The patient is responding well to antibiotics, but there haven’t been many patients diagnosed so it’s hard to accurately tell what the prognosis is.”

Dr Griffin said fewer than 100 cases had been diagnosed worldwide. Some had been fatal, but treatment was available.

He said contamination of some heater-cooler units used in open-heart surgery since 2012 led to about the bacteria last year.

“Clinicians need to be aware of this bacteria and highly cautious of patients in the at-risk group who present with symptoms including prolonged, unexplained fever or weight loss,” Dr Griffin said.

“The main message for patients who have had open-heart surgery and have symptoms is to see a doctor who can order the right tests.

“Clinicians should pay particular attention to the research and cases that are published because it’s such a recent discovery we need all the data available to improve the way we identify and treat patients.”

Dr Griffin said the issue was likely to continue to challenge hospital infection-control measures, as the bacterium had re-emerged in heater-cooler units despite intensified cleaning and monitoring regimens.

MRI-Â鶹´«Ã½Ó³»­’s Dr Evan Bursle, from the Â鶹´«Ã½Ó³»­ Faculty of Medicine and , and Dr Chris Coulter from Pathology Queensland collaborated on the research.