Antibiotic-resistant microbes ‘date back 450m years’
The study findings provide targets for research to design new antibiotics and disinfectants that specifically eliminate enterococci.
Antibiotic-resistant microbes date back 450 million years, according to new research which suggests that the ancestors of leading hospital ‘superbugs’, known as the enterococci, lived in the intestines of ancient land mammals.
US scientists looked at the evolutionary history of these pathogens, which have become leading causes of antibiotic-resistant infections in hospitals.
Co-corresponding author Ashlee M Earl said that by analysing the genomes and behaviours of today’s enterococci, the research team were able to “rewind the clock back to their earliest existence and piece together a picture of how these organisms were shaped into what they are today”.
Bacteria arose nearly four billion years ago. When animals first arose in the sea during the Cambrian Explosion 542 million years ago, bacteria learned to live in and on them. A hundred million years later, animals crawled onto land and took their microbes with them. Whilst some bacteria protects and serves animals, others live in the environment, and others cause disease.
Writing in the journal Cell, researchers said all species of enterococci - including those never found in hospitals - were naturally resistant to dryness, starvation, disinfectants and many antibiotics.
The team discovered enterococci lived in the intestines of land animals that are now extinct, including dinosaurs and the first millipede-like organisms to crawl on land. New species of enterococci were found to appear when new types of animals appeared. This includes those that arose after crawling onto land for the first time, as well as those that arose after mass extinctions - particularly the greatest mass extinction, the End Permian Extinction, which took place 251 million years ago.
For land animals, intestinal microbes are excreted as faeces which dry out and the microbes mostly die over time. However, this is not the case with enterococci, which are unusually hardy and can withstand drying out and starvation, scientists say.
“We now know what genes were gained by enterococci hundreds of millions of years ago, when they became resistant to drying out, and to disinfectants and antibiotics that attack their cell walls,” explained study leader Michael S Gilmore.
“These are now targets for our research to design new types of antibiotics and disinfectants that specifically eliminate enterococci, to remove them as threats to hospitalised patients.”
RCVS Knowledge has welcomed Professor Peter Cockcroft as editor-in-chief for Veterinary Evidence. 
