Methicillin Resistant Staphylococcus aureus (MRSA)
What is MRSA?
S. aureus, a gram-positive cocci, is one of the most versatile, persistent human pathogens, and is ubiquitous in the environment, thriving particularly in warm, moist places. It can be the causative organism for a variety of infections (including wound infection, pneumonia, urinary tract infection, and bacteremia), and has an extraordinary ability to develop antibiotic resistance.
Penicillin (PCN) was initially the drug of choice for treatment of S. aureus, after its introduction in the early 1940's, but by the end of the 1950's was virtually useless because of beta-lactamase-producing strains which were highly resistant to PCN. In the 1960's semi-synthetic PCNs (methicillin, oxacillin, nafcillin, etc) were developed which were not inactivated by beta-lactamase, but by 1961 the first strain of methicillin resistant S. aureus (MRSA) was identified in Great Britain. During the 1960's and early 1970's MRSA was a minor problem in the United States, however since 1975 there has been a progressive and alarming increase in MRSA. A CDC study, conducted by Dr. Robert Haley, et. al., showed an increase in the rate of MRSA from 2% of S. aureus in 1975 to 18% in 1981 in medical school affiliated hospitals. While MRSA is more common in teaching hospitals, strains have been found in a variety of U.S. hospitals and other health care facilities. MRSA strains may be primarily associated with nosocomial infections, but community reservoirs do exist. Once drug resistant staphylococci have become entrenched in a hospital, eradication is very difficult.
MRSA is identified at LLUMC by sensitivity reports ordered through the Clinical Lab. As recommended by the National Committee for Clinical Lab Standards (NCCLS), lab reports at LLUMC will show resistance to oxacillin, not methicillin (therapeutic equivalent). Control measures should be instituted as soon as the sensitivity report is received.
Who is at risk of getting MRSA?
Patients who have prolonged or repeated stays in the hospital or who have had invasive devices or procedures (including surgery) are at a higher risk of getting MRSA. Also, if a patient has been treated with lots of antibiotics, their chances of getting MRSA are increased. Antibiotics reduce the number of helpful bacteria in the body. Without a supply of these helpful bacteria, the body has a harder time fighting off infection.
Where can MRSA be found?
MRSA can be found in the blood, sputum, urine, and wounds, or wherever it can be carried by blood.
Colonization vs. infection
People who carry MRSA are said to be "colonized." Many kinds of bacteria can live in (colonize) your body without causing an infection. In fact, everyone is colonized by many kinds of bacteria. Being infected means bacteria are multiplying and the body is trying to defend itself against them. Principle site for colonization is the nares. Approximately 80% of adults are found to harbor S. aureus in the nose at one time or another. Since MRSA is another strain of S. aureus, this is why nare cultures are taken when we screen for eradication.
How can MRSA be spread?
S. aureus, including MRSA, is primarily spread via direct or indirect contact. In the health care setting S. aureus is most frequently transmitted by inadequate handwashing, either by a colonized health care worker, or carried from one patient to another on the hands of health care personnel.
Control measures used in cases of MRSA at Loma Linda University Medical Center are very stringent, due to the increased side effects and cost of alternative antibiotics. Health care workers often react to these control measures with fear that they are at risk for disease. This is not the case, since MRSA is no more virulent than methicillin sensitive S. aureus, only more difficult to treat. The extra precautions are instituted to prevent nosocomial patient spread and to prevent MRSA from becoming entrenched in LLUMC's environment.
Hospital Epidemiology monitors MRSA patients closely. A patient with identified MRSA infection or colonization is placed in "CONTACT" Precautions per LLUMC Policy M-50 Standard and Transmission-based Precautions. "CONTACT" precautions for these patients include a private room, gown and gloves for ALL persons entering the room for any reason. Change gloves after contact with infective material. After the removal of gloves, wash hands immediately. Patients in "CONTACT" precautions are not allowed to walk freely within the hospital. Isolation is required for these patients to keep the spread of MRSA at a minimum and to decrease the risk of environmental contamination to other areas or patients. Patients in MRSA isolation are allowed to visit outdoors if approved by Hospital Epidemiology and certain instructions are followed. Disposable food trays are not required.
If a patient needs to leave the nursing unit for a procedure within the hospital, the receiving department must be notified to prepare appropriate precautions prior to the patient’s arrival. The goal while transporting a patient with MRSA is to avoid contamination of the transporting healthcare worker as well as contamination of the hospital environment. At a minimum, a pair of gloves should be brought along during transport in case direct contact with the patient is necessary. A gown should not be needed, unless major contact with the patient is anticipated. The environment should not be contaminated with dirty gloves. Doors and elevator buttons should be touched with clean, ungloved hands.
Very few antibiotics are effective against the MRSA. The most commonly used one is vancomycin. The more it is used, the more chance there is that the MRSA organism will build up resistance to it.
To avoid developing resistant organisms, the following are good guidelines:
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Do not demand antibiotics from your doctor. They will not help some infections.
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When taking antibiotics, do not discontinue the medicine as soon as you feel better - take them as prescribed and contact your doctor if you feel worse or think the medicine is causing side effects.
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Throw out any unused antibiotics.
In the hospital and the community, the most important practice to prevent the spread of any organism, including MRSA, is good handwashing.
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