What is Methicillin-resistant Staphylococcus aureus (MRSA)?

From the Guidelines

For confirmed MRSA infections, vancomycin (30 mg/kg/d in 2 divided doses IV) is the recommended first-line treatment, as stated in the 2014 update by the Infectious Diseases Society of America 1.

Treatment Options

The treatment of MRSA infections depends on the severity of the infection and the patient's overall health.

• For severe infections, vancomycin is the preferred treatment, with a dosage of 30 mg/kg/d in 2 divided doses IV 1.
• For less severe skin infections, oral options include:
  • Trimethoprim-sulfamethoxazole (1-2 double-strength tablets bid po) 1
  • Clindamycin (600 mg every 8 h IV or 300-450 mg qid po) 1
  • Linezolid (600 mg every 12 h IV or 600 mg bid po) 1
  • Doxycycline, minocycline (100 mg bid po) 1

Prevention and Control

To prevent the spread of MRSA, it is essential to practice good hand hygiene, cover wounds, avoid sharing personal items, and complete the full antibiotic course 1.

• Healthcare settings should implement contact precautions for infected patients.
• Proper wound care is essential, including incision and drainage for abscesses. The guidelines for the management of MRSA infections are based on evidence-based recommendations, as stated in the 2011 clinical practice guidelines by the Infectious Diseases Society of America 1.

Key Considerations

• MRSA has evolved resistance through acquiring the mecA gene, which alters penicillin-binding proteins that beta-lactam antibiotics target, necessitating these alternative treatment approaches.
• The treatment of MRSA infections should be guided by the severity of the infection, the patient's overall health, and the susceptibility of the infecting organism to antibiotics.

From the Research

Treatment Options for MRSA

• Vancomycin remains a widely used treatment option for MRSA infections, with a focus on individualized dosing to achieve optimal pharmacokinetic/pharmacodynamic (PK/PD) targets 2
• Alternative treatment options include linezolid, daptomycin, and ceftaroline, which have shown promise in treating MRSA infections, particularly in cases where vancomycin is not effective or is associated with increased risk of resistance 3, 4
• Linezolid has been shown to be a potential first-line treatment for MRSA bacteremia, with comparable effectiveness and safety to vancomycin, teicoplanin, or daptomycin 5
• Daptomycin and linezolid may be advantageous in certain clinical conditions, such as bloodstream infections and pneumonia, respectively, due to their pharmacokinetic/pharmacodynamic properties 6

Considerations for Treatment

• The choice of treatment for MRSA infections depends on various factors, including the type and severity of the infection, patient characteristics, and the presence of resistance or susceptibility to specific antibiotics 2, 3
• Combination therapy with β-lactams and vancomycin or daptomycin is increasing, although further studies are needed to determine its effectiveness in more invasive infections, such as bacteremia and endocarditis 3
• The emergence of resistance to new anti-MRSA antimicrobials, including ceftaroline, highlights the need for continued monitoring and development of new treatment options 3

Pharmacokinetic/Pharmacodynamic Considerations

• Pharmacokinetic/pharmacodynamic (PK/PD) considerations are important in identifying clinical conditions where alternative treatments, such as daptomycin and linezolid, may be advantageous compared to vancomycin 6
• The long half-lives and complex PKs of lipoglycopeptides may preclude their use in critically ill patients, while anti-MRSA cephalosporins, such as ceftaroline, may be reserved for patients with MRSA infections due to concerns about increased resistance 2