The common gram-negative bacterium Pseudomonas aeruginosa stands out as a true comic book villain among microbes. Capable of slipping through defenses to infiltrate the most sterile spaces, this devious killer earns its ranking among the World Health Organization‘s list of priority 1 pathogens.
Most people encounter P. aeruginosa in everyday environments and come away unscathed. However, under the right circumstances, this bacterium can take advantage of the smallest gaps in our defenses, leading to runaway infections.
An international team of researchers, led by scientists from the University of Cambridge, investigated the evolutionary history of this opportunistic threat. They developed a genetic family tree of 596 closely related strains based on 9,829 bacterial samples from human, animal, and environmental sources worldwide, some dating back to 1900.
Their findings revealed that only 21 strains are responsible for the vast majority of infections. The rapid evolution of these strains over the past two centuries has transformed P. aeruginosa into a dangerous infectious agent. Each year, more than half a million people die from P. aeruginosa infections, which are particularly challenging to treat due to the bacterium’s extensive antibiotic resistance.
P. aeruginosa’s adaptability is astonishing, allowing it to survive in environments as diverse as jet fuel and virtually pure water. This adaptability makes it a significant problem in healthcare settings, where even stringent hygiene practices cannot always prevent infections. Hospital patients with chronic lung conditions such as cystic fibrosis (CF) and bronchiectasis are especially susceptible.
The researchers discovered that several infectious strains of the bacterium have evolved a strong affinity for people with CF. These strains have developed targeted methods to exploit the compromised health of CF patients, helping them avoid destruction by the host’s immune system. These CF-specific strains continue to evolve by exchanging resistance factors, much like sharing recipes at a family gathering.
This discovery exemplifies P. aeruginosa’s ability to use its survivability to carve out new niches in extreme environments, allowing it to gather the tools for further evolutionary leaps.
“From a clinical perspective, this study has revealed important information about Pseudomonas,” says senior author Andres Floto, a respiratory biologist and director of the UK Cystic Fibrosis Innovation Hub at the University of Cambridge. “The focus has always been on how easily this infection can spread between CF patients, but we’ve shown that it can spread with worrying ease between other patients, too.”
Understanding how easily highly resistant forms of the pathogen can spread highlights the need for ultra-efficient screening and isolation measures. P. aeruginosa is unlikely to ever become an easily defeated foe, but knowing its strengths is vital to preventing it from evolving into an even more dangerous threat.
“Our research on Pseudomonas has taught us new things about the biology of cystic fibrosis and revealed important ways we might be able to improve immunity against invading bacteria in this and potentially other conditions,” says Floto.
Read Now:Spotting Close-Approaching Asteroids: Challenges and Insights
