December 7, 2021

I, Science

The science magazine of Imperial College

“The first death in relation to this outbreak occurred on the sixth of January. The second occurred on the thirteenth of January. And, as you may have heard on the news overnight or this morning, the third death occurred late yesterday evening.”

Visibly shaken neonatal consultant Clifford Mayes made this statement at a press conference recorded by the BBC on Friday 20 January 2012. His words followed the deaths of three premature babies at the Royal Hospital in Belfast. Dr Mayes went on to explain that all had died following infection with Pseudomonas aeruginosa – a tough, antibiotic-resistant, rapidly evolving superbug. It may be less well-known than MRSA (pictured), but it is increasingly problematic in hospitals, infecting vulnerable patients with weaker immune systems.

It has been known for some time that Pseudomonas and other disease-causing bacteria synchronise certain behaviours – such as toxin release – for maximum effect; a phenomenon known as quorum sensing. But whilst we have held an understanding of the principles of quorum sensing for a while, only now has a group of researchers demonstrated the circumstances under which it is most beneficial to the bacteria themselves.

“We show that there is a benefit to doing this at high cell density rather than low cell density,” says Steve Diggle, leader of the laboratory at the University of Nottingham that published the findings. “It’s always been assumed that density is important. But you’ve got to actually show it’s important, which is what we’ve done.”

The findings could be helpful for developing “quorum quenchers”, compounds that stop this communication behaviour before the bacteria take action. So could these “quenchers” stop bacteria such as Pseudomonas and MRSA from releasing those fatal toxins?

Diggle isn’t sure. “The whole idea of using quorum quenching compounds will probably not be the sole answer. What we need to do in this era of antibiotic resistance is a kind of dual therapy with antibiotics – weaken the bacteria to make traditional antibiotics more useful again. That could be the way forward.”

But patients will have to wait to see the benefits of this research. “I think that we’re a number of years off actually having something that works in the lab,” Diggle concludes. With clinical trials to follow even this achievement, Mayes and his team at the Royal Hospital will have to continue to use traditional methods for some time yet in the fight against superbugs such as Pseudomonas aeruginosa.