Discovery of antibiotic-resistant bacteria Antibiotic-resistant bacteria cut off from the outside world for more than four million years have been found in a deep cave. The discovery is surprising because scientists had thought bacteria built up resistance to antibiotics after being repeatedly exposed to the treatment.
However, the resistant bugs from Lechuguilla Cave in New Mexico, U.S., have had no contact with humans, suggesting the environment may be to blame.
They are thought to have picked up their resistance from natural anti-bacterial chemicals in the environment.
'Our study shows that antibiotic resistance is hard-wired into bacteria. It could be billions of years old, but we have only been trying to understand it for the last 70 years,' said Dr Gerry Wright, from McMaster University in Canada, who has analysed the microbes.
'This has important clinical implications. It suggests that there are far more antibiotics in the environment that could be found and used to treat currently untreatable infections.'
The research is published in the online journal Public Library of Science ONE.
Lechuguilla Cave, which reaches to a depth of 1,604 feet, is one of the largest and deepest unspoiled cave systems in the world.
It is surrounded by an impermeable layer of rock discovered in 1986, and access to the cave is limited to a handful of expert cavers and researchers each year.
The bacteria were collected from some of the deepest and most isolated recesses of the cave and tested for antibiotic resistance.
Researchers found that while none of the bacteria are harmful to humans, almost all were resistant to at least one antibiotic and some to as many as 14 different drugs.
Overall, resistance was seen to virtually every antibiotic in current use by doctors.
'Most practitioners believe that bacteria acquire antibiotic resistance in the clinic,' said Dr Wright.
'As doctors prescribe antibiotics, they select for members of the community that are resistant to these drugs.
Over time, these organisms spread and eventually the bacteria that commonly cause these infections are all resistant.
'In extreme cases these organisms are resistant to seven or more drugs and are untreatable using traditional treatment, and doctors must resort to surgery to remove infected tissue.
'The actual source of much of this resistance is harmless bacteria that live in the environment.'