MRSA is caused by a strain of staph bacteria that's become resistant to the beta-lactam antibiotics commonly used to treat ordinary staph infections. For years the majority of MRSA infections have occurred in hospitals and health care settings, these infections are known as health care-associated MRSA (HA-MRSA). HA-MRSA infections typically are associated with invasive procedures or devices, such as surgeries, intravenous tubing or artificial joints. Another type of MRSA infection occurs in the wider community mostly among healthy people, and is known as community-associated MRSA (CA-MRSA). It's spread by skin-to-skin contact. At-risk populations include groups such as high school wrestlers, child care workers and people who live in crowded conditions.
Staphylococcus aureus bacteria live in the nose and on the skin of most healthy human beings. The bacteria are generally harmless unless they enter the body through a cut or other wound. Once in the body MRSA like all Staph infections causes a red swollen infected area with an abscess, or small red bumps that resemble pimples, boils, or spider bites. If the bacteria burrow deeper in to the body it can cause potentially life-threatening infections in bones, joints, surgical wounds, the bloodstream, heart valves and lungs.
MRSA is the result of decades of often unnecessary antibiotic use. For years, antibiotics have been prescribed for colds, flu and other viral infections that don't respond to these drugs. Even when antibiotics are used appropriately, they contribute to the rise of drug-resistant bacteria because they don't destroy every germ they target. Bacteria live on an evolutionary fast track, so germs that survive treatment with one antibiotic soon learn to resist others.
References:
Zeller, J. L. (October 2007). MRSA Infections. The Journal of the American Medical Association, 298 (15). Retrieved from http://jama.ama-assn.org/cgi/content/full/298/15/1826
Todar, K. (n.d.). Todar’s Online Textbook of Bacteriology. Retrieved from http://www.textbookofbacteriology.net/staph.html
Rolain, J., Francois, P., Hernandez, D., Bittar, F., Richet, H., Fournous, G., . . . Raoult, D. (2009). Genomic analysis of an emerging multiresistant Staphylococcus aureus strain rapidly spreading in cystic fibrosis patients revealed the presence of an antibiotic inducible bacteriophage. Biology Direct, 4 (1). doi: 101186/1745615041
Tortora, G. J., Funke, B. R., Case, C. L. (2010). Microbiology: An introduction (10th ed) (pp. 586-589). San Francisco, CA: Pearson Benjamin Cummings.
