Science Bulletins: MRSA—The Evolution of a Drug-Resistant Superbug

The human body is a diverse bacterial ecosystem. Humans are hosts to trillions of microbes, most of which are harmless or even beneficial. But a new study shows how one bacterium traveled from humans to farm animals and back to humans, developing resistance to antibiotics along the way. Staph infections in humans are usually treatable, but this new strain, called methicillin-resistant Staphylococcus aureus (MRSA), does not respond to antibiotics. Researchers found that it developed resistance while in farm animal hosts, through exposure to high level of antibiotics in their diet. Identifying the evolutionary processes of disease agents that transfer between species may help scientists determine how to prevent and treat emerging diseases. Related Links: Staphylococcus aureus CC398: Host Adaptation and Emergence of Methicillin Resistance in Livestock http://mbio.asm.org/content/3/1/e00305-11.full PubMed Health: MRSA http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004520/ CDC: Methicillin-resistant Staphylococcus Aureus (MRSA) Infections http://www.cdc.gov/mrsa/ US Food and Drug Administration http://www.fda.gov/ New York Times: Steps Set for Livestock Antibiotic Ban http://www.nytimes.com/2012/03/24/health/fda-is-ordered-to-restrict-use-of-antibiotics-in-livestock.html