Methicillin Resistant Staphylococcus Aureus

Aka: Methicillin Resistant Staphylococcus Aureus, Methicillin Resistant Staph Aureus, MRSA, MRSA Infection, MRSA Encounter, Vancomycin intermediate Staphylococcus aureus, Vancomycin resistant Staphylococcus aureus

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II. Risk Factors: Community acquired MRSA (unique from hospital acquired cases)

  1. Athletes (Contact Sports with frequent abrasions)
  2. Crowded living 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

III. Risk Factors: Comorbidy or medical environment exposure

  1. Recent hospitalization (especially if Antibiotics administered during hospitalization)
  2. Nursing facility residents
  3. Recent Corticosteroid therapy
  4. Injection drug use (Intravenous drug use)
  5. HIV positive patients (especially if CD4<500 cells/mm3)
  6. Hemodialysis patients
  7. Diabetes Mellitus
  8. Pressure Ulcer history
  9. Prior MRSA history
  10. Close contact with MRSA colonized person

IV. Evaluation

  1. Base treatment on culture and sensitivity

V. Characteristics

  1. Typically involves Skin and Soft Tissue Infections
    1. Consider in delayed Wound Healing or refractory Cellulitis
    2. Now MRSA appears to be most common organism
  2. Consider as respiratory superinfection following Influenza

VI. Labs

  1. Rapid MRSA assay (e.g. nasal PCR for MRSA)

VII. Management: Outpatient

  1. Avoid Antibiotics for abscess <5 cm without signs of Cellulitis
  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 to 2 DS tabs orally twice daily
        1. May use double the standard dose for MRSA (two DS tabs twice daily)
      2. Child: 8 to 12 mg/kg of trimethoprim divided bid
    2. Doxycycline
      1. Adults: 100 mg orally twice daily
    3. Clindamycin (Cleocin)
      1. Resistance rates in MRSA Infection have risen in U.S. (Septra and Doxycycline are preferred)
      2. Risk of induced resistance (identified with the D-Zone Test)
      3. Adult: 300 to 450 mg orally every 6 hours (or IV 600 mg every 8 hours)
      4. Child: 10 to 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
      1. Risk of rapid development of induced resistance if used alone
      2. Used in combination with above agents or with Vancomycin to increase efficacy
      3. No additional benefit in MRSA bacteremia when added to MRSA effective agents
      4. Tremblay (2013) Ann Pharmacother 47:1045-54 [PubMed]
      5. Thwaites (2018) Lancet 391(10121): 668-78 [PubMed]

VIII. Management: Inpatient

  1. Vancomycin
    1. Preferred agent for inpatient treatment
    2. Adult: 15 mg/kg IV every 12 hours
    3. Child: 40 mg/kg IV divided every 6 hours
    4. Adjust for Chronic Kidney Disease
    5. Increasing Vancomycin resistant Staphylococcus aureus
      1. Try other Antibiotics above prior to Vancomycin (Decreases Vancomycin resistance risk)
      2. Vancomycin intermediate Staphylococcus aureus (1 mcg/ml or more)
      3. Vancomycin resistant Staphylococcus aureus (MIC 16 mcg/ml or more)
  2. New agents with MRSA activity (only for severe cases or in Vancomycin resistance, e.g. Vancomycin MIC >1 mcg/ml)
    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. May be preferred over Vancomycin (toxin suppression, no nephrotoxicity) in Skin and Soft Tissue Infections
        1. Yue (2013) Cochrane Database Syst Rev (1):CD008056 [PubMed]
    4. Tygacil (Tigecycline)
      1. Adult: 100 mg IV load, then 50 mg IV every 12 hours
    5. Teflaro (Ceftaroline)
      1. Adult: 600 mg IV every 12 hours (lower dosing for Renal Insufficiency)
  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)
    3. Clindamycin (risk of induced resistance)

IX. Complications

  1. MRSA colonized patients
    1. Higher risk of infection
    2. Higher risk of death due to Antibiotic Resistance

X. 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. Wash sheets, towels and clothing in hot water
    5. Remove colonized catheters
    6. Clean under Fingernails and keep nails short
    7. Do not share towels, razors, linens
    8. All contacts should frequently wash hands after touching patient's personal items (e.g. laundry)
    9. Consider disinfecting commonly touched surfaces (e.g. door knobs) twice weekly with bleach or lysol
  3. Identify source case of infection
    1. Swab nasopharynx of patients and staff near outbreak
  4. Decolonization Indications and Approach
    1. Indications
      1. Two MRSA Skin Infections at different sites over a six month period despite wound care, hygiene
      2. Decolonization of close contacts of these patients may be considered (e.g. household)
    2. Primary Strategy
      1. Bactroban applied twice daily to nares and wounds for 5-10 days
        1. Apply blueberry sized ointment in each nostril with cotton swab
        2. Press nostrils together with fingers and massage gently
    3. Other Methods
      1. Chlorhexidine (Hibiclens) showers for 5-14 days
      2. Dilute bleach baths (1/4 cup per 13 gallons water) for 15 minutes twice weekly for 3 months
  5. References
    1. (2016) Presc Lett 23(8)
    2. (2019) Presc Lett 26(1)

XI. References

  1. (2005) Lexi-comp Drug Database
  2. Carvey and Glauser (2023) Crit Dec Emerg Med 37(11): 23-9
  3. Glauser (2014) Crit Dec Emerg Med 28(11): 2-10
  4. Bamberger (2005) Am Fam Physician 72:2474-81 [PubMed]
  5. Breen (2010) Am Fam Physician 81(7): 893-9 [PubMed]
  6. Michel (1997) Lancet 349:1901-6 [PubMed]
  7. Kauffman (1993) Am J Med 94:371-8 [PubMed]
  8. Stevens (2009) Ann Intern Med 150(1): 11 [PubMed]

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