MRSA Screening

This collection of tests detects the presence of, and sometimes evaluates the genetic characteristics of, Methicillin Resistant Staphylococcus aureus (MRSA). MRSA are strains of Staphylococcus aureus, or “staph,” bacteria that are resistant to the antibiotic methicillin and to related “beta lactam” antibiotics such as oxacillin. First appearing in the early 1960s, MRSA cases and outbreaks have been a problem in confined populations such as hospitals, prisons, and nursing homes ever since. MRSA strains have caused a significant number of severe skin, lung, bone, and heart-related staph infections that have proven difficult to treat and in some cases proven fatal. Most hospitals have instituted measures to attempt to eradicate MRSA and to control the spread of MRSA from person to person. This has been a challenge as staph is a common bacterium that colonizes the skin and in the nose of about 25-30% of the population. In the past, only about 0.8 % of the colonizing staph was MRSA, but in the last decade this has risen above 1%, and a few studies of select populations have shown MRSA colonization rates in those studied as high as 9%.

Since the 1960’s, there have been occasional outbreaks of MRSA outside of the hospital setting, but in the last few years the number of cases has greatly increased and concern among doctors and other healthcare workers is growing. In the community, MRSA is causing infections in young, previously healthy people with no apparent risk factors. Studies of these cases and outbreaks are showing that the bacteria is being spread in the community by MRSA colonized or infected people through close contact (such as sports or a day care) and through contact with contaminated objects (such as sports equipment, shared towels, razors, etc.) Often the infection it causes will be a lingering skin infection that may be first reported as a “spider bite.” Sometimes it is a lung infection that persists.

Studies have also shown that the community acquired strains of MRSA were frequently genetically distinct from those found in the hospital setting (indicating that they developed separately), resistant to antibiotics routinely prescribed to treat skin infections, and in some cases have proven to be especially virulent, producing toxins and causing an invasive infection. These strains of MRSA are now being found in the hospital as well, as infected and/or colonized patients and healthcare workers bring them into this setting.

A nasal swab is collected by rotating a swab inside of each nostril. Occasionally, a swab of a wound infection site or of a skin lesion is collected.