Methicillin Resistant Staphylococcus Aureus

1. See Also
   1. Staphylococcus aureus
2. Epidemiology
   1. High risk for elderly in institutional settings
   2. MRSA colonized patients
      1. Higher risk of infection
      2. Higher risk of death due to Antibiotic Resistance
   3. Community acquired MRSA
      1. Unique from hospital acquired cases
      2. Higher risk groups
         1. Athletes (contact sports with frequent abrasions)
         2. Crowded ling conditions
         3. Military recruits
         4. Pacific Island residents
         5. Natives of Alaska
         6. Native Americans
         7. Prison inmates
         8. Men who have sex with men
         9. Intravenous drug use
         10. Close contact with MRSA colonized person
      3. Accounts for 60% of staph infections in some states
         1. Alaska
         2. California
         3. Georgia
         4. Texas
      4. Recent outbreaks in midwest community settings
         1. Minnesota
         2. North Dakota
         3. (1999) MMWR Morb Mortal Wkly Rep 48:707-10
3. Evaluation
   1. Base treatment on culture and sensitivity
4. Characteristics
   1. Typically involves Skin and Soft Tissue Infections
      1. Now MRSA appears to be most common organism
   2. Consider as superinfection following Influenza
5. Management: Outpatient
   1. Consider not using antibiotics
      1. Abscess <5 cm
   2. Precautions
      1. Avoid beta lactam antibiotics (not effective)
      2. Dicloxacillin and Cephalexin are not effective for MRSA
      3. Avoid Fluoroquinolones due to resistance
   3. Topical Antibiotics with efficacy against MRSA (Impetigo, Folliculitis)
      1. Mupirocin 2% (Bactroban) Apply three times daily for 5 days
      2. Retapmulin 1% (Atabax) Apply twice daily for 5 days
   4. Oral antibiotics with efficacy against MRSA
      1. Trimethoprim Sulfamethoxazole (Bactrim, Septra)
         1. Adult: 1-2 DS tabs orally twice daily
            1. Use double the standard dose for MRSA (two DS tabs twice daily)
         2. Child: 8-12 mg/kg of trimethoprim divided bid
      2. Doxycycline or Minocycline
         1. Adults: 100 mg orally twice daily
      3. Clindamycin (Cleocin)
         1. Risk of induced resistance (identified with the D-Zone Test)
         2. Adult: 300-450 mg orally every 6 hours (or IV 600 mg every 8 hours)
         3. Child: 10-20 mg/kg orally every 8 hours (or IV 24-40 mg/kg divided q8 hours)
      4. Linezolid (Zyvox)
         1. Adult: 600 mg orally or IV every 12 hours
         2. Child: 10 mg/kg orally or IV every 12 hours
         3. Very expensive, and not first-line
         4. Serious drug interactions with MAO inhibitors and SSRIs
         5. Bioavailability is same for oral and IV
      5. Rifampin (risk of induced resistance)
         1. Used in combination with above agents
6. Management: Inpatient
   1. Vancomycin
      1. Try other antibiotics above prior to Vancomycin
         1. Decreases Vancomycin resistance risk
      2. Preferred agent for inpatient treatment
      3. Adult: 15 mg/kg IV every 12 hours
      4. Child: 40 mg/kg IV divided every 6 hours
      5. Adjust for Chronic Kidney Disease
   2. New agents with MRSA activity (only for severe cases)
      1. Synercid (Quinupristin-Dalfopristin)
      2. Cyclic Lipopeptide: Cubicin (Daptomycin)
         1. Adult: 4 mg/kg IV every 24 hours
         2. Complicated Skin and Soft Tissue Infections
         3. Do not use for Pneumonia
         4. Associated with Myopathy and signficant gastrointestinal symptoms
      3. Zyvox (Linezolid)
         1. See Dosing above
         2. Complicated Skin and Soft Tissue Infections
         3. Complicated Pneumonia
      4. Tigecycline (Tygacil)
         1. Adult: 100 mg IV load, then 50 mg IV every 12 hours
   3. First-line antibiotics
      1. Vancomycin is only first-line agent in many cases
      2. Linezolid is also first-line for MRSA, complicated Pneumonia
   4. Alternative antibiotics
      1. Linezolid
      2. Daptomycin (do not use in Pneumonia)
7. Prevention
   1. MRSA colonization in physicians is common
   2. Control of contagious spread
      1. Careful and frequent hand washing or Alcohol gels
      2. Proper handling of bodily secretions
      3. Isolate infected patients (cover wounds)
      4. Remove colonized catheters
      5. Clean under Fingernails and keep nails short
      6. Do not share towels, razors, linens
   3. Identify source case of infection
      1. Swab nasopharynx of patients and staff near outbreak
      2. Consider treating MRSA carriers
         1. Bactroban applied twice daily to nares and wounds for 5-10 days
         2. Chlorhexidine (Hibiclens) showers for 5-14 days
         3. Dilute bleach baths (1/4 cup per 13 gallons water) for 15 minutes twice weekly for 3 months
8. References
   1. (2005) Lexi-comp Drug Database
   2. Bamberger (2005) Am Fam Physician 72:2474-81
   3. Breen (2010) Am Fam Physician 81(7): 893-9
   4. Michel (1997) Lancet 349:1901-6
   5. Kauffman (1993) Am J Med 94:371-8
   6. Stevens (2009) Ann Intern Med 150(1): 11