Researchers Unveil Molecular Details of How Bacteria Propagate Antibiotic Resistance

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http://www.sciencedaily.com/releases/2012/07/120726135238.htm

ScienceDaily (July 26, 2012) — Fighting "superbugs" -- strains of pathogenic bacteria that are impervious to the antibiotics that subdued their predecessor generations -- has required physicians to seek new and more powerful drugs for their arsenals. Unfortunately, in time, these treatments also can fall prey to the same microbial ability to become drug resistant. Now, a research team at the University of North Carolina at Chapel Hill (UNC) may have found a way to break the cycle that doesn't demand the deployment of a next-generation medical therapy: preventing "superbugs" from genetically propagating drug resistance.

The team will present their findings at the annual meeting of the American Crystallographic Association (ACA), held July 28 -- Aug. 1 in Boston, Mass.

For years, the drug vancomycin has been the last-stand treatment for life-threatening cases of methicilin-resistant Staphylococcus aureus, or MRSA. A powerful antibiotic first isolated in 1953 from soil collected in the jungles of Borneo, vancomycin works by inhibiting formation of the S. aureus cell wall so that it cannot provide structural support and protection. In 2002, however, a strain of S. aureus was isolated from a diabetic kidney dialysis patient. This particular strain would not succumb to vancomycin. This was the first recorded instance in the United States of vancomycin-resistant Staphylococcus aureus, or VRSA, a deadly variant that many now consider one of the most dangerous bacteria in the world.

Former UNC graduate student Jonathan Edwards (now at the Massachusetts Institute of Technology), under the guidance of chemistry professor Matthew Redinbo, led the research team that sought a detailed biochemical understanding of the VRSA threat. They focused on a S. aureus plasmid -- a circular loop of double-stranded DNA within the Staph cell separate from the genome -- called plW1043 that codes for drug resistance and can be transferred via conjugation ("mating" that involves genetic material passing through a tube from a donor bacterium to a recipient).