The discovery suggests the resistance is primeval, natural and embedded in the genetic heritage of microbes.

It also demonstrates that such resistance emerged millions of years before the widespread introduction of penicillin to fight infection during World War II.

Writing in the journal PLoS ONE, a team from Canada’s McMaster University and Ohio’s University of Akron describe how 93 percent of all strains of bacteria collected from deep inside Lechuguilla Cave at Carlsbad Caverns in New Mexico are already resistant to at least one of the antibiotics currently used.

The cave bacteria were also found to use two methods to resist antibiotics that had never been seen before.

“It's awe-inspiring," said Gerard D. Wright, a microbiologist from the Institute for Infectious Disease Research at McMaster University. “It gives you real respect for the genetic diversity and the ability of these organisms to evade toxic molecules.”

Wright adds there might be undiscovered antibiotics among the cave samples that could be used to treat currently untreatable infections.

Photo: Carlsbad Caverns