Methicillin-Resistant Staphylococcus Aureus (MRSA)
MRSA is a type of Staphylococcus aureus bacteria that has developed resistance to methicillin and other beta-lactam antibiotics, causing infections that range from skin and soft tissue infections to life-threatening invasive disease. 1, 2
Definition and Characteristics
MRSA is characterized by:
- A strain of Staphylococcus aureus that has acquired resistance to methicillin and other beta-lactam antibiotics (penicillins, cephalosporins)
- Resistance mediated by the mecA gene, which is often associated with the Panton-Valentine leukocidin (PVL) toxin in community-acquired strains 1
- Classification into two main types:
- Healthcare-associated MRSA (HA-MRSA): Typically multi-drug resistant
- Community-acquired MRSA (CA-MRSA): Generally susceptible to more non-beta-lactam antibiotics 2
Epidemiology
- MRSA has become a major nosocomial pathogen worldwide 3
- In 2005, an estimated 94,360 cases of invasive MRSA disease occurred in the United States 1
- Initially almost exclusively healthcare-associated, MRSA began emerging in community settings in the mid-1990s 1
- Transmission occurs primarily through:
- Direct skin-to-skin contact
- Contact with contaminated surfaces
- Breaks in the skin barrier
- Poor hygiene practices 2
Clinical Presentations
MRSA can cause a wide spectrum of infections:
Skin and Soft Tissue Infections (most common)
- Impetigo, folliculitis, furuncles/boils, carbuncles, cellulitis, abscesses 2
Invasive Infections
Complications
- Sepsis with purpura fulminans
- Waterhouse-Friderichsen syndrome
- Necrotizing fasciitis
- Pyomyositis 1
Diagnosis
- Clinical presentation with appropriate risk factors
- Culture and susceptibility testing from infected sites
- Rapid diagnostic tests for MRSA detection
- Screening of high-risk individuals or during outbreaks 2
Treatment
Treatment depends on the type and severity of infection:
Skin and Soft Tissue Infections
- Incision and drainage for abscesses (primary treatment)
- Antibiotic therapy based on local MRSA prevalence:
Invasive Infections
- Serious MRSA infections should be treated with parenteral vancomycin 4
- For vancomycin allergic patients, teicoplanin is an alternative 4
- For multi-resistant MRSA (mrMRSA), combination therapy with rifampicin and fusidic acid is recommended 4
- Alternative agents for resistant strains or treatment failures:
Prevention
Personal hygiene practices:
- Regular handwashing
- Immediate showering after sports/activities
- Avoiding sharing personal items 2
Wound management:
- Keeping wounds covered with clean, dry bandages
- Proper care for skin breaks 2
Environmental measures:
- Regular cleaning of high-touch surfaces
- Disinfection of shared equipment
- Proper laundering of clothing and linens 2
Decolonization strategies for recurrent infections:
- Nasal mupirocin
- Chlorhexidine body washes or dilute bleach baths 2
Special Considerations
Children: Avoid doxycycline in children under 8 years; vancomycin or clindamycin for hospitalized children with complicated infections 2
Athletes: Can return to play after completing at least 72 hours of antibiotic therapy and meeting specific criteria (no new lesions for 48 hours, no draining lesions) 2
Vancomycin-resistant strains: VISA/VRSA infections may require combination therapy or newer agents 2
MRSA remains a significant clinical challenge requiring prompt identification, appropriate antimicrobial therapy, and comprehensive prevention strategies to reduce its impact on morbidity and mortality.