Bacteria in dirt may be “born” with a resistance to antibiotics, which could help shed light on the problem of drug-defying “superbugs,” Canadian researchers said Thursday.
They tested 480 different bacteria found in soil and discovered that every single one had some resistance to antibiotics — meaning they had evolved a mechanism for evading the effects of the drugs.
The findings, published in the journal Science, could help explain why bacteria so quickly develop resistance to antibiotics, and why drug companies must constantly develop new ones.
“It explains where these things come from in the first place,” Gerry Wright, chair of Biochemistry and Biomedical Sciences at Ontario’s McMaster University, said in a telephone interview. “This work could prove to be extremely valuable to the drug development process.”
Wright’s team dug up 480 strains of Streptomyces bacteria and tested them for resistance to various antibiotics.
“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,” they wrote in their report.
‘A logical place to start’
These particular bacteria do not infect people, but Wright believes the findings almost certainly apply to other species of microbes.
“It turns out that Streptomyces make lots of antibiotics,” Wright said. “Anything that ends in ’mycin’ comes from streptomycin -- vancomycin, streptomycin.”
That was why they chose this group of bacteria.
“We were curious to see where these things might come from in the first place, so it seemed that was a logical place to start. I expect lots of these (drug-resistant) genes are peppered all over the microbial community,” Wright said.
They exposed the bacteria to known antibiotics and then searched for genes that were activated when the microbes survived.
“We found old mechanisms and new mechanisms,” Wright said.
“We found a brand-new resistance mechanism to an antibiotic called telithromycin,” he said, referring to Aventis’ 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.
Almost as soon as penicillin was introduced in the 1940s, bacteria began to develop resistance to its effects, prompting researchers to develop many new generations of antibiotics.
But their overuse and misuse 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 said his findings do not get doctors off the hook. He said they still must prescribe antibiotics only when they are needed, and stress to patients the need to use them properly.
Soil bacteria live in a constant kind of arms race, making antibiotics to protect themselves against other bacteria, and then evolving antibiotic resistance to evade the antibiotics made by other bacteria.
“Their coping tactics may be able to give us a glimpse into the future of clinical resistance to antibiotics,” Wright said.