A patient who says they have a "spider bite" should make you think of Staphylococcus aureus — including methicillin-resistant S. aureus (MRSA), which CDC classes as a "serious threat." MRSA can be resistant to several antibiotics, and it can cause serious trouble in healthcare facilities: bloodstream infections, pneumonia, surgical site infections, sepsis and death. Finding and treating it quickly helps stop it spreading.
Who carries it, and how it spreads
- About 2 in 100 people carry MRSA, possibly more in certain populations. Most never develop a serious infection.
- About 1 in 3 people (33%) carry S. aureus in the nose, its main site of colonization, usually without illness.
- In healthcare settings, MRSA usually spreads through direct contact with an infected wound or from contaminated hands. People who are colonized — carrying it with no signs of infection — can pass it on.
- Risk is higher for people who have surgery, have medical devices inserted in their body, or inject drugs.
- Outside hospitals, MRSA skin infections are common in the general community.
What infection looks like
Skin and soft tissue infections (SSTIs), carbuncles and abscesses are the most commonly reported presentations. Most S. aureus skin infections, MRSA included, appear as a bump or infected area that may be red, swollen, painful, warm to the touch, full of pus or other drainage, and accompanied by fever.
CDC encourages clinicians to consider MRSA for any SSTI compatible with S. aureus, especially a purulent one: a fluctuant or palpable fluid-filled cavity, a yellow or white center, a central point or "head," draining pus, or pus that can be aspirated with a needle and syringe. MRSA's role in cellulitis without an abscess or purulent drainage is less clear, because cultures are rarely taken.
Testing
| Question | How to answer it |
|---|---|
| Is the patient carrying MRSA? | Rub a cotton-tipped swab in the nose or on the skin |
| Is MRSA causing this infection? | Only laboratory testing for the bacteria can tell |
Treatment
- Incision and drainage is the main treatment for MRSA skin infections; antibiotics may also be needed.
- For severe infections that don't respond to initial treatment, culture and susceptibility testing should guide the choice of antibiotic.
- Decolonization: topical medicines and antiseptics can reduce the amount of S. aureus on a person's body.
- Follow-up: skin infections can become more serious, so discuss a follow-up plan with the patient in case new symptoms appear or theirs do not improve within 48 hours.
The Infectious Diseases Society of America's 2011 clinical practice guidelines cover treatment of MRSA infections in adults and children.
Prevention
Numerous studies show that prevention efforts reduce MRSA infections, and success depends on action at the facility level, from both healthcare providers and leadership. CDC's National Healthcare Safety Network publishes MRSA rates in U.S. hospitals.
Sources
Based on "Clinical Overview of Methicillin-resistant Staphylococcus aureus (MRSA) in Healthcare Settings," Centers for Disease Control and Prevention; a work of the United States government in the public domain. Further guidance: CDC's infection control guidance for MRSA in healthcare facilities and strategies to prevent S. aureus in acute care facilities; the SHEA/IDSA/APIC practice recommendation; and the IDSA treatment guidelines.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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