Bacteria in soil may show how superbugs develop resistance

Jan 22 2006

According to Canadian researchers bacteria in dirt may be "born" with a resistance to antibiotics, and studying bacteria in the soil may provide key clues to understanding how the superbugs develop resistance to antibiotics.

The Canadian scientists tested different soil bacteria and found every single one had some resistance to major classes of antibiotics which means they had evolved a mechanism for evading the effects of the drugs.

This they say could maybe explain why bacteria are so skilled at developing resistance to antibiotics, and why drug companies must constantly develop new ones.

The researchers say the soil serves as an under-recognized source of resistance that has the potential to reach clinics.

There has long been concern about drug-defying superbugs, such as MRSA, which doctors are no longer able to treat with traditional antibiotics.

Doctors are constantly being warned to use antibiotics sparingly, as bacteria seem to have an amazing ability to resist their effect.

The researchers found the resistance among the soil bacteria to one of the most commonly prescribed antibiotics, vancomycin, was identical to that found in disease-causing bugs in the hospital setting.

They also found evidence of resistance to a new antibiotic drug called telithromycin which was only approved in 2004.

The team led by Gerry Wright, chair of Biochemistry and Biomedical Sciences at Ontario's McMaster University, dug up 480 strains of Streptomyces bacteria and tested them for resistance to various antibiotics, and found without exception, every strain was found to be multi-drug resistant to seven or eight antibiotics on average, with two strains being resistant to 15 of 21 drugs.

These particular bacteria do not apparently infect people, but Wright believes the findings almost certainly apply to other species of microbes.

They also found a brand-new resistance mechanism to the antibiotic drug Ketek, only approved in 2004.

Ketek was designed to overcome resistance to antibiotics, but one of the bacteria Wright tested evolved a way to prevent it from working.

When penicillin was introduced in the 1940s, bacteria immediately began to develop resistance to its effects, prompting researchers to develop many new generations of antibiotics.

But the overuse and misuse of antibiotics have helped fuel the rise of drug-resistant "superbugs".

The U.S. Centers for Disease Control and Prevention says 70 percent of infections that people get while in the hospital are resistant to at least one antibiotic.

Wright says doctors must prescribe antibiotics only when they are needed, and stress to patients the need to use them properly.

The findings are published in the journal Science.