Image caption The infection has been on the rise over the past decade in patients

A dangerous infection which is becoming more common in people with cystic fibrosis can spread between patients, UK researchers say in The Lancet.

Doctors previously thought the Mycobacterium abscessus bacteria could only be caught from water and soil.

But hospitals around the world may now have to change the way patients are treated, the study says.

Around 3-10% of cystic fibrosis patients in Europe and the US are infected with the hard-to-treat bug.

There are around 9,000 people with cystic fibrosis in the UK although around one-in-25 people carries the faulty gene which causes the condition.

It affects the internal organs, especially the lungs and digestive system, by clogging them with thick sticky mucus which makes it hard to breathe and digest food.

We believe the infection gets aerosolised, for example, when people cough - and because this bacteria is tough it hangs around in the air Dr Andres Floto, Papworth Hospital, Cambridge

Researchers writing in The Lancet do not know exactly why Mycobacterium abscessus - which is distantly related to the bacteria that causes tuberculosis - is more likely to infect people with cystic fibrosis but it could be related to problems with the immune system.

It causes lung damage, and can be incredibly hard to treat with infected patients needing months of treatment with toxic drugs.

Although the infection has been on the rise over the past decade, doctors always believed it could not spread between humans.

But by looking at DNA from almost 170 samples of the bacterium, and using that to create a family tree, researchers found that it can indeed spread from person to person.

Infection control

Study leader Dr Andres Floto, research director of the Cystic Fibrosis Unit at Papworth Hospital in Cambridge and principal investigator at the Cambridge Institute for Medical Research, said the results had prompted them to completely rethink their infection control, despite already having strict policies in place.

He explained they already treated all in-patients in individual rooms without exposing them to other patients and out-patient clinics were set up so individuals did not have direct contact with each other.

"But despite that we were seeing transmission events in hospital which tells us that transmission is likely to be indirect," Dr Floto said.

"We are doing more research into that but we believe it gets aerosolised, for example, when people cough and because this bacteria is tough it hangs around in the air."

All inpatients at Papworth are now treated in negative pressure rooms to prevent the spread of airborne bugs and those with the infection are cared for away from the cystic fibrosis unit.

"And in outpatients for people with this bug, we use clinic rooms only once and then not for other patients until the next day when it has been deep cleaned."

Dr Floto said his team had already been in touch with hospitals in the UK and abroad to inform them of their findings and encourage them to change their practices and prevent the infection spreading as much as possible.

"Our results will help to protect patients from this serious infection."

Co-author Professor Julian Parkhill, head of pathogen genomics at the Wellcome Trust Sanger Institute, said: "By sequencing the complete genomes of bacteria we can accurately describe where they have emerged from and how they pass from person to person.

"This new information has led to rapid changes in how people with cystic fibrosis are cared for in hospital to protect them from this emerging threat."

Jo Osmond, director of Clinical Care and Commissioning at the Cystic Fibrosis Trust, said: "We will work closely with clinicians and the NHS to ensure appropriate measures are in place to deal with this issue.

"It is reassuring that this issue has been picked up early and that we are working positively to put in place measures to ensure cross-infection risks are reduced to a minimum.

"People with cystic fibrosis who have concerns about this issue should speak to their clinician."