MRSA—do I need to be afraid?
By Laurence Degelsmith, MD
November 2, 2007
We are all seeing a lot of press lately about the latest superbacteria: MRSA. I know there is a lot of anxiety and fear about contracting this new threatening bug.
In actuality, methicillin-resisant Staph aureus, abbreviated MRSA, has been around for many years but essentially was limited to hospital and nursing home environments. We as medical professionals have been dealing with and treating this bug in chronically ill and hospitalized patients for several decades, but recently MRSA has spread its reach to the young and healthy, which is some cause for concern. Don’t panic yet --it’s not all bad news. We can limit our risk of infection as well as the possibility of spreading it to others who might be in greater danger of having serious complications from MRSA.
A bacteria, not a virus
MRSA is classified a bacteria, not a virus. It is a type of Staphylococcus (Staph) bacteria that lives on our skin and in our mucus membranes, particularly the nose and throat. Approximately a third of the population is a carrier of Staph and can transmit it to others without actually developing any signs of infection. The vast majority of this Staph is MSSA (methicillin-sensitive Staph aureus) but the percentage of Staph that is MRSA is growing (up to three percent in some studies). MSSA is easily treatable with common antibiotics such as Amoxicillin, Erythromycin or Keflex, but MRSA is resistant to most common antibiotics, including those just mentioned. There are a few oral antibiotics that can be effective against MRSA, but these are few and not always successful depending on the exact strain of MRSA being treated. Each strain of MRSA has different genetic subtypes which are currently being studied. It is important for doctors to consider which strain of MRSA they suspect of causing a particular infection before treating because certain strains are more sensitive to the specific antibiotics used to treat MRSA.
MRSA is now divided into the two subtypes: HA-MRSA, hospital acquired, and CA-MRSA, community acquired. They are genetically different and have different antibiotic susceptibilities that affect which antibiotics will be effective in treating a suspected MRSA infection. The CA-MRSA is what all the excitement is about, because healthy people are now being diagnosed with MRSA infections when previously they were restricted to hospitalized or chronically ill patients. Thirty years ago, MRSA constituted about two percent of all invasive Staph infections. That number has jumped to over sixty percent in the last few years, primarily because of the overuse of antibiotics for illnesses that do not require them such as colds, bronchitis, sore throats. In addition to the over prescription of antibiotics, there is a widely held belief that the use of antibiotics in animal feeds and those given as supplements to poultry and other animals meant for human consumption has also contributed to antibiotic resistance. The Staph bacteria have essentially developed an immunity to the common antibiotics, which is why we’re seeing so much resistance these days and such a high percentage of MRSA among cultured soft tissue infections.
MRSA presentation—soft tissue infections
CA-MRSA and MSSA cause a similar spectrum of disease in healthy people. These are typically soft tissue infections ranging from pimples to abscesses (boils). The majority of MRSA bacteria contain a gene which in turn produces a tissue destroying toxin called a leukocidin. This leukocidin helps the bacteria break through cell membranes in soft tissue of the body, forming abscesses. Initially, they are sometimes confused with spider bites, since they often present as red raised lesions with or without drainage of pus. Rarely, CA-MRSA can become invasive and life-threatening in previously healthy persons by causing necrotizing pneumonia, sepsis, necrotizing fasciitis (flesh eating bacterial infection) among a few other types of infections. Remember that these severe infections are not common, which is why they show up in the news when diagnosed. Both CA-MRSA and HA-MRSA can cause more severe infections in the elderly, immune compromised and children. Children have not yet developed a strong immune system, which puts them at greater risk for complications from MRSA.
CDC identifies groups at higher risk
On their website, the CDC notes that several groups of people are at a higher risk of being exposed to the CA-MRSA bacteria. These include “inmates in correctional facilities, competitive sports participants, military recruits, day care attendees, men who have sex with men, and Native Americans. Factors common to these groups include crowding, frequent skin-to-skin contact between individuals, participation in activities that result in compromised skin surfaces, sharing of personal items that may become contaminated with wound drainage, and challenges in maintaining personal cleanliness and hygiene.” Frequent exposure to antibiotics and limited access to health care also puts one at risk. Transmission of MRSA can be controlled by strict adherence to frequent hand washing, covering all exposed wounds and not sharing personal items such as towels in the locker room.
Standard treatment
The majority of soft tissue infections can be treated primarily with incision and drainage of the pus. This has always been true with simple abscesses regardless of what bacteria are involved. Antibiotics have no effect on a localized collection of pus. This is still the case even, with suspected MRSA infections. Antibiotics are indicated for patients with large abscesses, focal collections of small abscesses or signs of spreading infection around an abscess. Soft tissue infections involving the face and hands should be treated with antibiotics. Patients with weak immune systems should probably also receive antibiotics after the incision and drainage of pus.
Last month I treated a ten year old boy who had a large abscess on his knee. I placed him on a common antibiotic called Augmentin, but the pus grew out MRSA so we had to call the family to change the antibiotic. I am now treating every skin infection or large abscess with a combination of antibiotics because we still need to treat for Strep (which is sensitive to most common antibiotics) as well as possible MRSA.
There are various antibiotic regimens found in the literature that have been recommended to treat soft tissue infections without knowing whether MRSA is present. The data is still out on which antibiotic combination is best. Patients with recurrent infections who are thought to be carriers of the MRSA bacteria are sometimes treated with an antibiotic ointment called Mupirocin to their outer nasal passages for five days to eradicate the bacteria from their system. A recurrent carrier state can occur however, even after this treatment.
Talk to your doctor or go to the emergency department if you think you have an abscess or skin infection. They will decide which treatment is necessary based on many factors, but remember, not all infections need antibiotics. Make sure to cover all skin infections and open wounds, even small ones, to prevent transmission of bacteria to others and to prevent someone else’s bacteria from invading your wound.
Author’s note: This article encompasses general guidelines taken from several published sources as well as my ten years of personal experience as an emergency physician. There will often be exceptions to the above guidelines because the risk vs. benefit ratio of using any medication will be different for each patient.
Laurence Degelsmith graduated from Horace Greeley High School in 1985, has an undergraduate degree from Washington University in Saint Louis, attended New York Medical College and did his residency in emergency medicine at the University of Michigan. He is an emergency department physician at Northern Westchester Hospital in Mt. Kisco and a member of the Chappaqua Volunteer Ambulance Corps.
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