Antibiotic resistance will lead to 10 million deaths per year by 2050,
surpassing cancer as a source of human mortality, predicts an influential report from the O'Neill Commission.
Small DNA molecules known as plasmids are one of the key culprits
in spreading the major global health threat of antibiotic resistance, revealed a new study led by scientists at the University of Oxford.
‘Small DNA molecules known as plasmids are one of the key culprits in spreading the major global health threat of antibiotic resistance.’
Using a novel experimental model, the international team of
researchers show that plasmids, which live inside bacteria and are known
to be a vehicle for transferring antibiotic resistance genes, can
accelerate the evolution of new forms of resistance - making them more
important to the process than previously thought.
The study is published in the journal Nature Ecology and Evolution
Senior author Professor Craig MacLean, a Wellcome Trust Research
Fellow in Oxford's Department of Zoology, said, "The discovery of
antibiotics revolutionized medicine by making it much simpler to treat
bacterial infections, and this had a big impact on human health and
longevity. For example, the use of penicillin led to a 90% decrease in
mortality caused by some forms of pneumonia. Unfortunately, few new
antibiotics have been discovered over the last 30 years, and resistance
to existing antibiotics has spread steadily because antibiotics are used
heavily in medicine. This is leading to a crisis in medicine, as we
have lost the ability to treat bacterial infections that can have
Professor MacLean said, "The spread of resistance genes in bacterial
populations is driven by simple, Darwinian selection: during antibiotic
treatment, bacteria with resistance genes have a higher reproductive
rate than sensitive bacteria, and, as a result, the use of antibiotics
causes the spread of resistance genes."
"Many of the most important resistance genes are found on plasmids,
which are small, circular DNA molecules that live inside bacteria.
Plasmids are capable of moving between bacteria and are usually thought
of as being important "vehicles" that transfer resistance genes between
"Our paper demonstrates that plasmids can also act as evolutionary
catalysts that accelerate the evolution of new forms of resistance. This
occurs because bacteria usually carry more than one copy of a plasmid,
which allows resistance genes carried by plasmids to rapidly evolve new
functions - in this case, the ability to degrade an antibiotic.
Additionally, plasmids automatically amplify the number of copies of
these new and improved resistance genes."
"These findings demonstrate a new role for plasmids in antibiotic
resistance and evolutionary innovation, and they highlight the threat
posed by plasmids to public health."
Professor MacLean added, "The conventional view of plasmids is that
they act as important vehicles that transfer resistance genes between
bacteria. Our research shows a new role for plasmids in antibiotic
resistance by demonstrating that plasmids drive the evolution of novel
forms of antibiotic resistance. While this does not offer any solutions
per se, it further highlights the importance of developing new methods
for tackling plasmids. For example, it may be possible to develop new
drugs that will block plasmid replication."