Methicillin-resistant Staphylococcus aureus infection
Methicillin-resistant Staphylococcus aureus (MRSA) is a mutation of very common bacterium spread easily by direct person-to-person contact. Once limited to large teaching hospitals and tertiary care centers, MRSA infection is now endemic in nursing homes, long-term care facilities, and community hospitals. It's also seen in patients who haven’t been hospitalized, as community-acquired MRSA infections are increasing.
Patients most at risk for MRSA infection include immunosuppressed patients, burn patients, intubated patients, and those with central venous catheters, surgical wounds, or dermatitis. Others at risk include those with prosthetic devices, heart valves, and postoperative wound infections. Other risk factors include prolonged hospital stays; extended therapy with multiple or broad-spectrum antibiotics; and close proximity to those colonized or infected with MRSA. Also at risk are patients with acute endocarditis, bacteremia, cervicitis, meningitis, pericarditis, and pneumonia.
Causes
MRSA enters health care facilities through an infected or colonized patient or a colonized health care worker. Although MRSA has been recovered from environmental surfaces, it's transmitted mainly by health care workers’ hands. Many colonized individuals become silent carriers. The most frequent site of colonization is the anterior nares (40% of adults and most children become transient nasal carriers). Other, less common sites are the groin, axilla, and the gut. Typically, MRSA colonization is diagnosed by isolating bacteria from nasal secretions.
In individuals where the natural defense system breaks down, such as after an invasive procedure, trauma, or chemotherapy, the normally benign bacteria can invade tissue, proliferate, and cause infection. Today, up to 90% of S. aureus isolates or strains are penicillin resistant, and about 50% of all S. aureus isolates are resistant to methicillin, a penicillin derivative, as well as to nafcillin and oxacillin. These strains may also resist cephalosporins, aminoglycosides, erythromycin, tetracycline, and clindamycin.
MRSA infection has become prevalent with the overuse of antibiotics. Over the years, this has given once-susceptible bacteria the chance to develop defenses against antibiotics. This new capability allows resistant strains to flourish when antibiotics kill their more-sensitive cousins.
Signs and symptoms
There are no signs and symptoms specifically for MRSA infection. It's often found incidently during culture.
Diagnosis
MRSA can be cultured from the suspected site with the appropriate method. For example, a wound can be swabbed for culture. Cultures of blood, urine, and sputum specimens will reveal sources of MRSA. Many laboratories use oxacillin disks to check for staphylococcus sensitivity when testing culture specimens; resistance to oxacillin indicates MRSA.
Treatment
To eradicate MRSA colonization in the nares, the physician may order topical mupirocin to be applied inside the nostrils. Other protocols involve combining a topical agent and an oral antibiotic. Most facilities keep patients in isolation until surveillance cultures are negative.
To attack MRSA infection, vancomycin is the drug of choice (see Vancomycin-resistant infections). A serious adverse effect (mostly caused by histamine release) is itching, which can progress to anaphylaxis. Some physicians also add rifampin, but whether rifampin acts synergistically or antagonistically when given with vancomycin is controversial.
Special considerations
❑People in contact with the patient should perform hand-hygiene before and after patient care.
❑Good hand-hygiene is the most effective way to prevent MRSA infection from spreading.
❑Use an antiseptic soap such as chlorhexidine. Bacteria have been cultured from worker's hands washed with milder soap. One study showed that, without proper hand-hygiene, MRSA could survive on health care workers’ hands for up to 3 hours. Chlorhexidine has a residual antimicrobial effect on the skin.
❑Contact isolation precautions should be used when in contact with the patient. A disinfected private room should be made available with dedicated equipment.
❑Change gloves when contaminated or when moving from a “dirty” area of the body to a clean one.
❑Instruct the patient's family and friends to wear protective clothing when they visit him, and show them how to dispose of it.
❑Provide teaching and emotional support to the patient and his family members.
❑Consider grouping infected patients together and having the same nursing staff care for them.
❑Don’t lay equipment used on the patient on the bed or bed stand. Be sure to wipe it with appropriate disinfectant before leaving the room.
❑Ensure judicious and careful use of antibiotics. Encourage physicians to limit their use.
❑Instruct the patient to take antibiotics for the full period prescribed, even if he begins to feel better.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
Other Book Chapters Related to Infection
Read excerpts from these other book chapters related to Infection:
Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2008 Williams & Wilkins.
More About Causes of Infection
» Next page: Puerperal infection (Professional Guide to Diseases (Eighth Edition))
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