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Antibiotic resistance predates medicine

Ancient arsenal Bacteria had the means to resist antibiotic attack even in prehistoric times, say Canadian researchers.

Their results are based on genetic analysis of bacterial DNA found in 30,000 year-old permafrost samples and raise further questions about the role of antibiotic resistance genes in evolution.

"It turns out that low doses of molecules that we call antibiotics don't necessarily kill bacteria, but trigger all kinds of fascinating reactions from gene expression to changing cell shape and maybe communication," says Dr Gerard Wright of McMaster University and lead author of the study that is published today in Nature.

According to Wright, the discovery overturns current dogma that resistance stems from clinical use because antibiotics have only been used in modern medicine for less than one hundred years.

"We were very curious to know where antibiotic resistance comes from because we could find it relatively easily in microorganisms, particularly in the soil," he says.

Wright says that this led them to turn to an area in the Yukon province where they could extract and analyse ancient soil samples preserved in a permanently frozen state.

The team showed that the samples contained DNA from plant and animal species that also existed 30, 000 years ago. They focussed their attention on a class of bacteria called Actinobacteria.

"They [actinobacteria] are remarkable machines that make most of our antibiotics and other molecules, which we turn into drugs including anticancer agents," says Wright.

Reservoir of drug resistance

The researchers used a technique called polymerase chain reaction, or PCR, to look for genes that could confer resistance to several major classes of antibiotics. They found a number of so-called 'resistance elements,' some of which are groups of genes.

"My guess would be that all the resistance elements we see today, we would probably find if we had the right tools," says Wright. "Most pathogenic organisms are not terribly drug resistant ... in comparison to environmental bacteria we study; yet with use of antibiotics they have been able to acquire these genes that are out there."

"The environment seems to be this great reservoir of resistance genes that can eventually end up in the clinic."

Wright says their research emphasises the need for caution around how we use antibiotics. "They need to be treated with tremendous respect," he says.

Microbiologist Professor Ruth Hall of the The University of Sydney, says the need to use antibiotics judiciously is already widely acknowledged and that we already know a lot more about where resistance genes comes from than what is described in the Canadian study.

"This research doesn't tell us anything new," says Hall. "Hundreds of microorganisms have genes related to antibiotic-resistant genes. The only resistant genes that matter are the ones that are circulating today ... bacteria are oblivious to the fact that we have developed antibiotics for clinical use."

She says there are a few notable examples of where researchers have documented exactly how particular antibiotic resistance genes have evolved, and where they have been transferred into pathogenic bacteria.

"It's more important to look at where the next resistant genes may come from - to have a good surveillance system in place," she says.