The Deadly Secret of One of the World's Most Dangerous Pathogens

Health experts have revealed that the common Gram-negative bacteria, Pseudomonas aeruginosa, deserves to be classified on the World Health Organization's list of priority pathogens 1.

Most of us encounter these bacteria in our everyday environments, and under the right conditions they may exploit the smallest gaps in our immune defenses to trigger disease.

In this regard, an international team of scientists studied the evolutionary history of these invasive species.

The team, led by scientists from the University of Cambridge, developed a genetic family tree of 596 closely related lineages, based on 9,829 bacterial samples taken from a variety of human, animal and environmental sources around the world, some dating back to 1900.

Scientists found that just 21 strains were responsible for the vast majority of infections, as a result of their rapid evolution.

The study showed that more than half a million people die annually as a direct result of P. aeruginosa infection, which is difficult to treat due to its resistance to antibiotics.

The adaptability of P. aeruginosa appears to be unlimited.

The infection particularly affects hospital patients with chronic lung diseases, such as cystic fibrosis (CF) and bronchiectasis, the scientists said.

The study found that many infectious strains of bacteria have developed targeted ways to exploit the poor health of cystic fibrosis patients, helping the bacteria avoid being destroyed by the host's immune systems.

It turns out that after finding a new safe space to survive inside the immune cells tasked with killing them, the cystic fibrosis strains of P. aeruginosa continued to evolve by swapping resistance factors with each other.

This discovery embodies the pathogen's ability to use its ability to survive to conquer new areas in harsh environments, giving it room to quietly gather the tools it needs to make another evolutionary leap.

“From a clinical perspective, this study has revealed important information about Pseudomonas,” says lead author Andres Floto, a respiratory biologist and director of the UK Cystic Fibrosis Innovation Centre at the University of Cambridge. “The focus has always been on how easily this infection spreads between cystic fibrosis patients, but we have shown that it can spread with alarming ease between other patients too.”

Knowledge of how easily highly resistant forms of pathogens can spread places greater pressure on the development of highly effective screening and isolation measures.

The study was published in the journal Science.