MRSA:  More Common Than Thought

If the estimates are correct, the number of deaths associated with methicillin-resistant Staphylococcus aureus (MRSA) – nearly 19,000 in the United States in 2005 – would exceed those attributed to HIV-AIDS, Parkinson’s disease, emphysema and homicide.

A recent study, published in the October 2007 issue of the Journal of the American Medical Association (JAMA), suggests that such infections may be twice as common as previously thought. By extrapolating data collected in nine places, the researchers estimated that 94,360 patients developed an invasive infection from the pathogen in 2005, and that nearly one of every five, or 18,650 of them, died. The study points out that it is not always possible to determine whether a death is caused by MRSA or merely accelerated by it.

A major difference between the new study and its predecessors is that it compiled confirmed cases of MRSA infection, rather than relying on coded patient records that sometimes lack precision. The study found higher prevalence rates and death rates for the elderly, African-Americans and men. The figures also varied by geography, with Baltimore’s incidence rates far exceeding those of the eight other locations.

MRSA, which was first isolated in the United States in 1968, causes 10 to 20 per cent of all infections acquired in health care settings, according to the CDC. The prevalence of invasive MRSA – when the bacteria has not merely colonized on the skin, but has attacked a normally sterile part of the body – is greater than the combined rates for other conditions caused by invasive bacteria, including bloodstream infections, meningitis and flesh-eating disease.

The JAMA study also concluded that 85 per cent of invasive MRSA infections are associated with health care treatment. Previous research had indicated that many hospitals and long-term care centres had become breeding grounds for MRSA because bacteria could be transported from patient to patient by doctors, nurses and unsanitized equipment.

Among other things, the findings in the JAMA study are likely to stimulate further an already active debate about whether hospitals and other medical centres should test all patients for MRSA upon admission.