An Overview of MRSA Infections

All About MRSA Infections

MRSA—an abbreviation for methicillin-resistant Staphylococcus aureus—is a bacterial “staph” infection that is resistant to many of the standard antibiotics.

Here’s what’s going on -– about 30% of all people are colonized (on their skin or in their nose) with Staphylococcus aureus. Colonization simply means that the Staphylococcus aureus bugs are harmlessly hanging out on our skin. No big deal, lots of microorganisms are hanging out on the outside of our bodies, Staphylococcus aureus is just one of them.

Staphylococcus AureusInfections, Years Ago

But if this Staphylococcus aureus gets to where it’s not supposed to be (say under your skin through a wound) and your immune system isn’t up to the challenge, you could end up with a “Staph” infection. “Staph” infections are an endemic (always present) infection in hospitals. Since 30% of people are colonized, it means “Staph” is everywhere. The “Staph” on the outside of your body gets inside or a nurse, after touching one patient, forgets to wash her hands and brings that patient’s Staphylococcus aureus bugs into your wound. Out in the world, all the Staphylococcus aureus isn’t a big deal -– we typically don’t have open wounds and our immune system is working great. But in the hospital, so many people have open skin (because of surgery, intravenous catheters, injuries, etc.) and their immune system is not 100% (because of illness), that “Staph” infections are common.

Antibiotics used to do a pretty good job fighting off “Staph” infections, until the Staphylococcus aureus began to adapt to the infections. Some of the Staphylococcus aureus, just by random chance, wasn’t as harmed by the antibiotics as others. Those organisms survived, multiplied and created more Staphylococcus aureus just like them –- resistant to antibiotics. Over time, these clever bugs became so resistant, that our arsenal of antibiotics just doesn’t work anymore. These new bugs are called “Methicillin Resistant Staphylococcus aureus” or MRSA. In 1961, the first MRSA bacteria were identified. Since then the strain is resistant not just to methicillin but to amoxicillin, penicillin, oxacillin, and many other antibiotics.

MRSA Infections Today

It is estimated that about 5% of people in the U.S. are colonized with MRSA (meaning, the MRSA is on their skin or in their nose, but they are not “infected” -– they are just carrying the bacteria around). People who are colonized have a higher risk of getting a MRSA infection -– for example, if a MRSA colonized person has an operation and the MRSA bacteria on his skin get into the wound, there could be a big problem.

Not only that, but the MRSA colonized, and the MRSA infected spread ​MRSA bacteria on surfaces in the hospital. It is estimated that 75% of patient rooms are contaminated with MRSA and VRE. Studies show that if a healthcare worker walks into a patient’s room and has no physical contact with the patient, her gloves will still be contaminated 42% of the time, just from touching surfaces in the room.

In 2005, there were 368,600 hospital stays for MRSA infection. This was triple the number of MRSA infections in 2000 and 10 times the number from 1995. Around 60% of all “Staph” infections in hospitals are now MRSA infections. Overall, MRSA is estimated to make up about 8% of all hospital acquired infections.

How Big Is The MRSA Infection Problem?

You’ve probably seen some news coverage about the MRSA problem and how big it is. I don’t want to spread sensation, but it is probably bigger than you think. Here are some factoids about MRSA to give you a better sense of the size of the MRSA infection problem:

MRSA Infection, U.S. Statistics

  • Number MRSA infected each year: 880,000 (2007 numbers)
  • % of hospital inpatients MRSA infected each year: 2.4%
  • Additional cost per MRSA infection: at least $10,000
  • Total cost of MRSA infections per year: around $8 billion
  • Average increased length of stay: 6 extra hospital days
  • % of people with MRSA infection who die from it: 5%
  • Number of MRSA infection deaths per year: 20,000 to 40,000

MRSA Infection, Globally

The global situation of MRSA is a bit harder to get a handle on. In Europe, the problem doesn’t seem quite as bad as in the U.S., partly because of differences in the prescribing of antibioitics and partly because of control measures that have been put in place (such as mandatory MRSA screening for all patients in some settings). That said, an epidemic is still brewing and as MRSA travels from the U.S. to Europe, expect to see the rates increase there too.

How Did This Happen?

There are several reasons we have a MRSA problem today. The most basic reason is that the Staph bacteria has developed resistance to methicillin and other antibiotics. Why? Antibiotic resistance evolves through selective pressure and random mutations. While the bacteria are replicating, a portion of those reproduced (by chance) may be mutants and able to survive even in the presence of antibiotics. Those that survive may be fit enough to go on to reproduce and cause illness. There is also a lot of data that overuse of antibiotics for decades has contributed to the problem. Because we overused antibiotics for decades. For example, antibiotics are often prescribed for viruses (like when people have the cold or the flu), this causes strain on the bacteria. When exposed to the antibiotics, some bacteria naturally are “hardier” than others. These bacteria survive (especially when the patients don’t take their full dose of antibiotics). They survive, reproduce and create resistant offspring. Continue the cycle for a couple of decades and a new strain of bacteria appears that is resistant to the antibiotic.

But it is not only the misuse of medications that is the problem, there is a lot of misuse of antibiotics in the animal industry. Those antibiotics end up in food and in the water supply, providing a low dose of antibiotics that helps create resistant bacteria.

What Does the Future Hold?

More of the same, lots more. There are no signs that MRSA and other infections are on the wane. As soon as one infection gets under control, it seems there are two to replace. While MRSA remains a huge concern (with no signs of slowing), two more superbugs are already poised to dethrone it: C. Diff. and A. Baumannii.

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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • CDC page on MRSA
  • Invasive Methicillin-Resistant Staphylococcus aureus Infections in the United States. R. Monina Klevens, Melissa A. Morrison, Joelle Nadle, Susan Petit, Ken Gershman, Susan Ray, Lee H. Harrison, Ruth Lynfield, Ghinwa Dumyati, John M. Townes, Allen S. Craig, Elizabeth R. Zell, Gregory E. Fosheim, Linda K. McDougal, Roberta B. Carey, Scott K. Fridkin, and for the Active Bacterial Core surveillance (ABCs) MRSA Investigators. JAMA. 2007;298(15):1763-1771.
  • John L. Zeller, MD, PhD, Writer; Alison E. Burke, MA, Illustrator; Richard M. Glass, MD, Editor. The Journal of the American Medical Association. Vol. 298 No. 15, October 17, 2007.
  • National Institutes of Health. Medline Plus. MRSA.
  • Statistical Brief #35. Healthcare Cost and Utilization Project (HCUP). July 2007. Agency for Healthcare Research and Quality, Rockville, MD.