MRSA, or methicillin-resistant Staphylococcus aureus, caused more than 94,000 life-threatening infections and nearly 19,000 deaths in the United States in 2005, most of them connected with healthcare settings. These numbers appear in the October 17, 2007, edition of the Journal of the American Medical Association (JAMA)1, as part of the most thorough study to date of trends in invasive MRSA infections.
MRSA stands for methicillin-resistant Staphylococcus aureus. This type of bacteria causes "staph" infections that are resistant to treatment with usual antibiotics.
MRSA occurs most frequently among patients who undergo invasive medical procedures or who have weakened immune systems and are being treated in hospitals and healthcare facilities such as nursing homes and dialysis centers. MRSA in healthcare settings commonly causes serious and potentially life-threatening infections, such as bloodstream infections, surgical site infections, or pneumonia.
In addition to healthcare-associated infections, MRSA can also infect people in the community at large. Such infections are generally mild and affect the skin with pimples or boils that can be swollen, painful and drain pus. These skin infections often occur in otherwise healthy people.
When we talk about the spread of an infection, we talk about sources of infection (where it starts) and the way or ways it spreads (the mode or modes of transmission).
In the case of MRSA, patients who already have a MRSA infection or who carry the bacteria on their bodies but do not have symptoms ("colonized" with MRSA bacteria) are the most common sources of transmission.
The main mode of transmission to other patients is through human hands, especially healthcare workers' hands. Hands may become contaminated with MRSA bacteria by contact with infected or colonized patients. If a healthcare worker doesn't wash with soap and water or use an alcohol-based hand sanitizer after contact with a patient, the bacteria can be spread when the healthcare worker touches other patients.
Along with MRSA, many significant infection-causing bacteria in the world are becoming resistant to the most commonly prescribed antimicrobial treatments. What causes this and what does it mean?
Antimicrobial resistance occurs when bacteria change or adapt in a way that allows them to survive in the presence of antibiotics designed to kill them. In some cases bacteria become so resistant that no available antibiotics are effective against them. At this time, treatment options still exist for healthcare-associated MRSA.
People infected with antibiotic-resistant organisms like MRSA are more likely to have longer and more expensive hospital stays, and may be more likely to die as a result of the infection. When the drug of choice for treating their infection doesn't work, they require treatment with second- or third-choice medicines that may be less effective, more toxic and more expensive.
MRSA infections are becoming more prevalent in healthcare settings. According to CDC data, the proportion of infections that are antimicrobial-resistant has been growing. In 1974, MRSA infections accounted for two percent of the total number of staph infections; in 1995 it was 22 percent; and in 2004 it was 63 percent.
Most MRSA infections appear to occur in healthcare settings, rather than out in the community. The 2007 JAMA study found that about 85 percent of all invasive MRSA infections were connected with healthcare settings. In contrast, about 14 percent of reported infections were considered to be community-associated, which means that the infection occurred in people without documented evidence of risks connected to a healthcare setting.
Interestingly, most of the serious MRSA infections were caused by bacterial strains traditionally associated with healthcare. However, the strains traditionally associated with transmission in the community are now being identified in healthcare settings, too.
In terms of numbers of people affected, it is estimated that in 2005 about 94,360 people developed a serious MRSA infection. About 18,650 persons died during a hospital stay of causes related to serious MRSA infections. People 65 years old or older were most likely to get an invasive infection, and black people were affected at twice the rate of whites, which could be due to higher rates of chronic illness among blacks.
"These numbers show that many families are being affected by these drug-resistant infections," said Denise Cardo, M.D., director of CDC's Division of Healthcare Quality Promotion.
The good news is that MRSA is preventable. "Healthcare facilities need to make MRSA prevention a greater priority. The closer we get to 100 percent compliance with CDC recommendations, the greater the impact on patient health and safety," Cardo said. The first step to prevent MRSA is to prevent healthcare infections in general. Infection control guidelines produced by CDC and the Healthcare Infection Control and Prevention Advisory Committee (HICPAC) are central to the prevention and control of healthcare infections and, ultimately, MRSA in healthcare settings.
- Healthcare-Associated Methicillin Resistant Staphylococcus aureus (HA-MRSA) - Overview, facts, prevention and control information for healthcare personnel, educational materials, more
- CDC Estimates 94,000 Invasive Drug-resistant Staph Infections Occurred in the U.S. in 2005. - Press Release: (October 16, 2007)
- Antibiotic/Antimicrobial Resistance - Gateway to resources both inside and outside CDC
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