Superbugs deploy ‘decoy flares’ like fighter jets to avoid being killed by antibiotics

The antibiotic of last resort fails to kill about a third of MRSA infections and scientists believe they have found out why

An MRSA bacterial cell releases decoys to evade an antibiotic (Imperial College London)

Scientists have discovered an astonishing new strategy deployed by superbugs in their evolutionary struggle with antibiotics – decoy “flares” which distract the drugs that would otherwise kill them.

About a third of MRSA bacteria, which kill thousands of people across the world, are largely immune to the current antibiotic of last resort.

In a new academic paper in the journal Nature Microbiology, researchers said they had found out a reason why. When it comes under attack, the bug can release “decoys” which the scientists compared to the flares used by warplanes to distract heat-seeking missiles.

The rise of antibiotic resistance is causing increasing alarm with the prospect of a return to the days when a minor cut in the garden could be fatal and major operations were impossible because of the risk of infection.

Dr Jonathan Pearce, head of infections and immunity at the Medical Research Council, which supported the research, said: “In the fight against antimicrobial resistance, we are desperately searching for new ways to treat bacterial infections like MRSA as they dangerously start to become resistant to even last-resort antibiotics.

“This study has uncovered a rather cunning tactic that these and possibly other bacteria use to evade current treatment and, armed with this new knowledge, we can begin to develop new and improved treatments to help tackle what is one of the biggest threats to global health.”

The use of decoys has never been seen before in MRSA, the researchers said, adding that they were now looking for a way to stop this from happening.

They are made from the same type of fat that makes up the outer layer of the superbug’s cells.

The antibiotic daptomycin normally latches onto this fat, drills a hole through the cell wall and kills the bacteria. But faced with a sea of fat decoys, they attack those instead and are used up.

One of the research team, Dr Andrew Edwards, of Imperial College London, said: “These fat molecules act in a similar way to the decoy flares released by fighter planes to avoid a missile.

“The antibiotic mistakenly targets the decoys, allowing the bacteria to evade destruction. This is the first time this decoy system has been seen in MRSA.”

A similar decoy mechanism has been found in E coli, leading the researchers to believe this may be a defence mechanism used by “many other bacteria”.

Further work led to the discovery that another antibiotic, called oxacillin, can partially prevent the release of the fatty decoys.

It is thought that even though a strain of MRSA bacteria might be resistant to both daptomycin and oxacillin, using the two drugs together could be an effective strategy. A team in Australia is currently carrying out a clinical trial of this technique.

And a next generation antibiotic, also in clinical trials, has shown signs of being able to stop the production of the decoys.