Studying drug resistance in soil bacteria may help defeat superbugs

Date: May-22-2014A new study suggests clues to overcoming drug resistance in superbugs may lie in

understanding why soil bacteria, despite having many drug-resistant genes, seem reluctant to

share them.

The ability of bacteria to swap genes is known to be an important driving force in the rise of

superbugs - microbes that are becoming increasingly resistant to drugs designed to kill them. The

rise of superbugs poses a serious threat to global public health. The World Health Organization

recently warned that common

infections may become killers unless we act now.

According to a recent threat report from the Centers for Disease Control and Prevention, around 2 million Americans every year become infected with drug-resistant bacteria, and at

least 23,000 die as a result of such infections. Many more die from other conditions that became

complicated because of drug-resistant infection.

Antibiotic resistance now accounts for $20 billion of annual health-care costs and 8 million

additional hospital treatment days in the US.

Soil bacteria have a large armoury of antibiotic-resistant genes

It is thus alarming to discover that bacteria that live naturally in the soil have a large

armoury of genes to fight off antibiotics. But a new study led by Washington University School of

Medicine (WUSTL) in St. Louis, MO, and published in the journal Nature, reveals that this large

armoury is not poised to contribute to antibiotic resistance in infectious bacteria.

Senior author Gautam Dantas, assistant professor of pathology and immunology at WUSTL,

hopes by studying the surprising lack of sharing of drug-resistant genes in soil bacteria, they

may find ways to reduce gene sharing in infectious bacteria, and also, as he explains:

"Soil bacteria have strategies for fighting antibiotics that we're only just starting to learn

about. We need to make sure the genes that make these strategies possible aren't shared with

infectious bacteria, because they could make the problem of drug-resistant infections much

worse."

The majority of drugs used to combat infection today come from soil microbes. For example

penicillin, the first successful antibiotic, originates from the soil fungus

Penicillium.

But unfortunately, widespread use of penicillin and other antimicrobial drugs has driven

bacteria to evolve ways of resisting them.

Resistance genes in soil bacteria 'not poised' for sharing with pathogens

Scientists studying antibiotic resistance in bacterial DNA have identified patterns of genetic

code that enable the microbes to share resistance genes. If a gene sits close to these "mobility

elements," then it is readily shared with other bacteria.

Scientists studying antibiotic resistance in bacterial DNA have identified patterns of genetic code that enable the microbes to share resistance genes.

Prof. Dantas and colleagues analyzed the DNA of bacteria found in 18 soil samples from

agricultural and grassland sites in Minnesota and Michigan.

Using a technique they helped to develop, they identified around 3,000 antibiotic resistance

genes in the soil bacteria. However, they were not situated close to mobility elements in the

bacteria's DNA.

They also found that individual drug-resistance genes were closely linked with particular

bacteria, suggesting they were not readily shared among species.

"We suspect that one of the primary factors that drives the sharing of antibiotic resistance

genes is exposure to new antibiotics," explains Prof. Dantas. "Because soil bacteria need many

thousands of years to develop new antibiotics, the bacteria in that community don't encounter

these threats anywhere near as often as disease-causing bacteria, which we regularly treat with

different antibiotics."

He says they were happy to discover that antibiotic resistance genes from soil bacteria are not

poised to jump suddenly into infectious bacteria. But he warns we need to do everything we can -

from the way we treat infections to the way we manage environments that harbor bacteria - to keep

the odds in our favor.

Funds for the study came from a number of organizations, including the National Institutes of

Health, the Children's Discovery Institute, the International Center for Advanced Renewable

Energy and Sustainability at Washington University, and the National Academies Keck Futures

Initiatives.

Meanwhile, Medical News Today recently learned how new agents may revitalize antibiotics to fight

superbugs. A study published in the Journal of the American Chemical Society showed it

may be possible to fight superbugs with conventional antibiotics by pairing the drugs with a new

class of metal-based agents called metallopolymers, which revitalize their potency.

Written by Catharine Paddock PhD

View all articles written by Catharine, or follow Catharine on:

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.