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MRSA (methicillin resistant staphylococcus aureus) is a type of staphylococcus bacteria (staph) that is resistant to beta-lactam antibiotics. MRSA is contagious and can cause life-threatening infection.
MRSA isn’t found in the natural environment (soil or water). It lives in the nose and on the skin of humans. MRSA is spread by coming in contact with an infected person or by exposure to a MRSA-contaminated object or surface that an infected person touches.
MRSA infections are classified as hospital-acquired (HA-MRSA) or community-acquired (CA-MRSA).
HA-MRSA is associated with exposure to intravenous catheters, surgical procedures like joint replacement, and contact with devices found in a hospital setting.
CA-MRSA is associated with conditions of close personal contact, poor hygiene, and exposure to contaminated objects.
About one in four healthy people are colonized by staphylococcus bacteria. Those who are colonized have the bacteria present in their skin and nasal passages, but the presence of the bacteria doesn’t make them ill. Historically, most staph was sensitive to beta-lactam antibiotics, such as penicillin, methicillin, and ampicillin. Some strains of staph developed resistance to beta-lactam antibiotics.
It is estimated that 2 percent of the population now carry a strain of staph that is resistant to beta-lactam antibiotics. Most of the staph infections that now occur in hospitals are caused by MRSA. Although aggressive infection control measures have decreased the incidence of HA-MRSA, the incidence of CA-MRSA is increasing.
Risks for HA-MRSA include:
Risks for CA-MRSA include:
The majority of MRSA infections remain restricted to the skin. HA-MRSA can cause severe illness, where the bacteria can spread to the blood, bones, and other tissue.
CA-MRSA usually causes skin infections. Areas that have been cut, scratched, or rubbed are vulnerable to infection. Areas of increased body hair—such as the buttocks, armpits, back of the neck, and beard—are more likely to be infected. Infected areas are red, swollen (fluid-filled) and painful to touch. The lesion may resemble an infected spider bite. Typically, there is yellow or white center and a central head. Pus and other fluids may drain from these lesions.
The spectrum of MRSA skin infections includes infection or abscess of hair follicles (furuncles), abscesses, and carbuncles (a mass of infected furuncles).
HA-MRSA can cause severe problems, such as pneumonia, urinary tract infections, sepsis, and bone infections. The symptoms of HA-MRSA include:
Diagnosis begins with health history assessment and physical examination. Cultures should be obtained from the site of infection using antiseptic techniques. Types of cultures obtained to diagnose MRSA include the following methods:
Samples of secretions are obtained with a sterile cotton swab and placed in a container for transport to the lab.
Patients who are able to cough can provide a sputum sample. Patients who are unable to cough, and those on ventilators, may need to have a respiratory lavage or bronchoscopy to obtain a sputum sample. Respiratory lavage and bronchoscopy involve the use of a bronchoscope. Under controlled conditions, the doctor inserts a thin tube called a bronchoscope through your mouth and into your lungs. The bronchoscope has a camera attached, so the doctor is able to see the lungs and collect a sample of secretions for culture.
In the majority of instances, cultures are obtained from a “clean catch” urine specimen. First, the area around the urethra is wiped with a sanitary moist wipe. A sterile container is used to collect urine mid-stream. Sometimes, urine has to be collected directly from the bladder. To do this, the doctor inserts a sterile tube called a Foley catheter into your bladder. Urine then drains from the bladder into a sterile container.
Positive blood cultures are proof of sepsis. Sepsis is the presence of bacteria in the blood. Bacteria can enter the blood from infections located in other parts of your body, such as the lungs, bones, urinary tract, and intravenous catheters.
Results from cultures generally take 48 hours. DNA testing that can identify MRSA within hours is becoming more widely available.
The CDC recommends the following criteria for making a diagnosis of CA-MRSA. All of the following criteria must be met:
MRSA can be sensitive to other antibiotics. Intravenous antibiotics are used to treat severe infections. Not all CA-MRSA infections are treated with antibiotics. The doctor may choose to drain an abscess, rather than treat with antibiotics.
Doctors at the Mayo Clinic recommend the following measures to help prevent CA-MRSA:
This is the first defense against spread of MRSA. Hands should be scrubbed for at least 15 seconds before drying them with a towel. Use another towel to turn off the faucet. Carry hand sanitizer that contains 60 percent alcohol to keep your hands clean when you don’t have access to soap and water.
Covering wounds can prevent pus or other fluids containing MRSA from contaminating surfaces or spreading the bacteria to others.
This includes towels, sheets, razors, clothing, and athletic equipment.
And don’t share towels.
If you have cuts or bruises, wash bed linens and towels in hot water with extra bleach. Dry with high heat. Wash gym and athletic clothes after each use.
People with MRSA in a hospital environment are isolated. Isolation prevents the spread of MRSA. Hospital personnel caring for patients with MRSA have to follow strict hand-washing procedures. Hospital personnel and visitors should wear protective garments and gloves to prevent contact with contaminated surfaces. Linens and contaminated surfaces should be properly disinfected.
Written by: Verneda Lights and Matthew Solan
Published on: Aug 20, 2012
Medically reviewed on: Aug 20, 2012: George Krucik, MD
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