Putting bacteria on birth control

Putting bacteria on birth control could stop the spread of drug-resistant microbes, and researchers at the University of North Carolina, Chapel Hill, have found a way to do just that, as they have discovered a key weakness in the enzyme that helps "fertile" bacteria swap genes for drug resistance.

Drugs called bisphosphonates, widely prescribed for bone loss, block this enzyme and prevent bacteria from spreading antibiotic-resistant genes. Interfering with the enzyme has the added effect of annihilating antibiotic-resistant bacteria in laboratory cultures. "Our discoveries may lead to the ability to selectively kill antibiotic-resistant bacteria in patients, and to halt the spread of resistance in clinical settings," explains Matt Redinbo, professor of chemistry, biochemistry and biophysics.

Antibiotic-resistant bacteria represents a serious public health problem. In the last decade, almost every type of bacteria has become more resistant to antibiotic treatment. These bugs cause deadly infections that are difficult to treat and expensive to cure. Every time someone takes an antibiotic, the drug kills the weakest bacteria in the bloodstream. Any bug that has a protective mutation against the antibiotic survives. These drug-resistant microbes quickly accumulate useful mutations and share them with other bacteria through conjugation--the microbe equivalent of mating.

Conjugation starts when two bacteria smush their membranes together. After each opens a hole in its membrane, one squirts a single strand of DNA to the other. Then the two go on their merry way, one with new genes for traits such as drug resistance. Many highly drug resistant bacteria rely on an enzyme, called DNA relaxase, to obtain and pass on their resistance genes. A mutation that provides antibiotic resistance can sweep through a colony quickly.

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The researchers analyzed relaxase because it plays a crucial role in conjugation. The enzyme starts and stops the movement of DNA between bacteria. "Relaxase is the gatekeeper, and it is also the Achilles' heel of the resistance process," points out Redinbo.

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COPYRIGHT 2008 Gale, Cengage Learning