Some Bacteria are Sneakier Than First Suspected

Posted September 9th, 2014 at 7:59 pm (UTC-4)
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This image shows two strains of E. coli bacteria (wild-type and GASP) competing with each other as they grow out on a flat surface. The wild-type bacteria appear green on the surface while the GASP bacteria appear red. (Robert Austin/Princeton University)

This image shows two strains of E. coli bacteria (wild-type and GASP) competing with each other as they grow out on a flat surface. The wild-type bacteria appear green on the surface while the GASP bacteria appear red. (Robert Austin/Princeton University)

The emergence and rapid growth of antibiotic resistant bacteria has become a serious worldwide health concern.

The World Health Organization said in its 2014 report on antimicrobial resistance that “without urgent, coordinated action, the world is heading towards a post-antibiotic era, in which common infections and minor injuries, which have been treatable for decades, can once again kill.”

Scientists have found that some infection causing bacteria can quickly evolve and mutate to a point where antibiotics that were created to destroy it become ineffective. But now a team of researchers from three American universities have found that these mutating microbes can be sneakier that had been suspected.

The researchers, writing in the journal Biomicrofluidics, found that among the tools used by bacteria to avoid harm or destruction is a built-in arsenal of hidden genetic weapons that helps it develop a number of different ways to evolve and mutate quickly while under stress due to antibiotic treatments, making the microbes much more adaptable and tougher to beat.

An electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped (USDA)

An electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped (USDA)

“Bacteria are clever – they have hidden ways to respond to stress that involve re-sculpting their genomes,” said Princeton University biophysicist and team leader, Robert Austin in a press release.  “It teaches us that antibiotics have to be used much more carefully than they have been up to this point,” he said.

Rather than using traditional test tubes or petri dishes, the researchers used unique fluid-filled microstructures in their experiments that were developed by Austin and his colleagues.  The research team said that they think their new devices represented a more natural environment for their investigations than traditional laboratory implements.

“In complex environments the emergence of resistance can be far more rapid and profound than would be expected from test tube experiments,” Austin said.

In previous studies, the researchers found that there are some “wild type” or non-mutated forms of Escherichia coli (E-coli) bacteria that can quickly evolve and develop a resistance to antibiotics.

So the team wondered if a mutated strain of E-coli, called GASP, would have the same type of antibiotic resistance as the “wild type” strain if it were exposed to the same drug.

Ciprofloxacin tablets (AJ Cann via Flickr/Creative Commons)

Ciprofloxacin tablets (AJ Cann via Flickr/Creative Commons)

To find out, the researchers sequenced the genomes of both “wild type” and the mutated GASP strains of E-coli bacteria that had been exposed to ciprofloxacin, an antibiotic medication known commonly as Cipro. The sequencing experiments showed that although the strains of the E-coli used different methods of genetic mutation, they all were able to develop comparable levels of antibiotic resistance.

Austin said that the research his team conducted revealed the wide range of tools bacteria can use to overcome stress and develop antibiotic resistance.

He also wondered about the effectiveness of other commonly used methods for killing potentially harmful microbes, such as using alcohol to sanitize germ ridden surfaces, and if bacteria would be able to develop a resistance to them as well.

Austin and his team are planning further tests.

Rick Pantaleo
Rick Pantaleo maintains the Science World blog and writes stories for VOA’s web and radio on a variety of science, technology and health topics. He also occasionally appears on various VOA programs to talk about the latest scientific news. Rick joined VOA in 1992 after a 20 year career in commercial broadcasting.

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