Vulnerable patients in hospitals across the country are at risk from a deadly bug found in water supplies that has already claimed the lives of two middle-aged women, a coroner has warned.

Yet despite the danger posed by the bug – Mycobacterium abscessus – there is no official advice on testing for it, on acceptable levels, or on how to protect vulnerable patients, said Keith Morton KC.

Mr Morton, assistant coroner for Cambridgeshire and Peterborough, has written to Health Secretary Steve Barclay about the risk following the deaths of Karen Starling, 54, and Anne Martinez, 65, at Royal Papworth Hospital in Cambridge, a heart and lung transplant centre.

A year ago, The Mail on Sunday revealed how both succumbed to M. abscessus infection after undergoing successful lung transplant operations in 2019.

They were operated on not long after the Royal Papworth opened its new hospital building that May. In November, at a joint inquest into their deaths, Mr Morton concluded they were likely to have picked up the bug from the building’s water supply.

VICTIM: Lung transplant patient Anne Martinez was killed by the bug

The Mail on Sunday revealed how both succumbed to M. abscessus infection after undergoing successful lung transplant operations in 2019. They were operated on not long after the Royal Papworth opened its new hospital building that May

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M. abscessus, which can be found in soil and municipal water supplies, poses little risk to most people as their immune systems are robust enough to repel it. But Mr Morton warned: ‘It is recognised M. abscessus poses a risk of death to those who are immunosuppressed. That will be so for many patients at specialist hospitals such as Royal Papworth and more generally for hospital patients.’

He said a current Health Department memorandum on safe water in hospitals ‘provides no relevant guidance’ on the bacteria – even though it did so for the better known pathogens legionella and pseudomonas.

There was no guidance on whether M. abscessus should be routinely tested for, none on what an acceptable level of the bug in water might be, and nothing on what additional measures should be taken to protect the particularly vulnerable.

Mr Morton added there was ‘evidence that the risk… is especially acute for new hospitals’ – something that might concern Ministers as they are in the process of building 40 more. To date, 34 patients at Royal Papworth have been infected with the bug.

Besides the deaths of mother-of-six Mrs Starling and teacher Mrs Martinez, lawyers believe there is a third victim, 26-year-old Aaron Green. He tested positive for a related bug, M. chelonae, after a heart and lung transplant in 2019 and died two years later.

Jennifer Hodgson, a public health lawyer at Irwin Mitchell, who represented the two women’s families, said: ‘Large public buildings with more complex water systems can be at greater risk of water contamination.’

Eilish Midlane, chief executive of the Royal Papworth, said: ‘We took immediate and extensive action to ensure patient safety as soon as this issue was identified.’

The Department of Health said it would respond to the coroner’s report ‘in due course’.