From the Guidelines
Vancomycin is the first-line antibiotic for treating serious MRSA infections, typically administered intravenously at 15-20 mg/kg every 8-12 hours. Alternative options include linezolid (600 mg IV/oral twice daily), daptomycin (4-6 mg/kg IV once daily), and trimethoprim-sulfamethoxazole (TMP-SMX) for less severe infections 1. For complicated skin infections, tedizolid (200 mg daily) or ceftaroline (600 mg IV every 12 hours) may be used. Treatment duration typically ranges from 7-14 days, depending on infection severity and site. For minor skin infections, clindamycin (300-450 mg oral four times daily) may be sufficient.
Key Considerations
- Antibiotic selection should be guided by susceptibility testing, infection site, and patient factors like kidney function and drug allergies 1.
- MRSA's resistance to beta-lactam antibiotics (including methicillin, oxacillin, and cephalosporins) occurs due to the mecA gene, which produces modified penicillin-binding proteins that prevent these antibiotics from disrupting cell wall synthesis.
- Treatment should include proper wound care for skin infections, drainage of abscesses when present, and removal of infected devices if applicable.
Oral Antibiotic Options
- Linezolid (600 mg oral twice daily) 1
- Trimethoprim-sulfamethoxazole (TMP-SMX) 1
- A tetracycline (doxycycline or minocycline) 1
- Tedizolid (200 mg daily) 1
Intravenous Antibiotic Options
- Daptomycin (10 mg/kg/dose IV once daily) 1
- IV linezolid (600 mg twice daily) 1
- IV ceftaroline (600 mg IV every 12 hours) 1
- IV vancomycin (15-20 mg/kg every 8-12 hours) 1
From the FDA Drug Label
The cure rates in microbiologically evaluable patients with MRSA skin and skin structure infection were 26/33 (79%) for linezolid-treated patients and 24/33 (73%) for vancomycin-treated patients Adjudication Committee success rates are shown in Table 17. Methicillin-resistant S. aureus 20/45 (44%) 14/44 (32%) 12.6% (−10.2,35.5)
Antibiotic coverage for MRSA:
- Linezolid and vancomycin are recommended antibiotics for MRSA infections, with cure rates of 79% and 73%, respectively, in microbiologically evaluable patients with MRSA skin and skin structure infection 2.
- Daptomycin also shows effectiveness against MRSA, with a success rate of 44% in patients with MRSA bacteremia, compared to 32% for the comparator (vancomycin or an anti-staphylococcal semi-synthetic penicillin) 3.
- Key points to consider when choosing an antibiotic for MRSA infections include:
- Efficacy: Linezolid and vancomycin have shown high cure rates in MRSA skin and skin structure infections.
- Resistance: Daptomycin has been effective against MRSA, but resistance can develop.
- Patient population: Pediatric patients with MRSA bacteremia have been treated with daptomycin, with a clinical success rate of 88% 3.
From the Research
Antibiotic Coverage for MRSA
The recommended antibiotics for Methicillin-resistant Staphylococcus aureus (MRSA) infections include:
- Vancomycin, which is considered the treatment of choice for MRSA bacteremia 4, 5, 6, 7, 8
- Ceftaroline fosamil, which has been shown to have comparable clinical outcomes to vancomycin and daptomycin in MRSA bacteremia patients 4
- Daptomycin, which is used as an alternative to vancomycin, especially in cases of severe infections or when vancomycin is not effective 4, 7, 8
- Linezolid, which has been shown to be effective against MRSA bacteremia, especially in cases with pulmonary complications, and may be considered as a first-line drug 7, 8
Dosage and Administration
- Vancomycin dosing for MRSA pneumonia in critically ill trauma patients should be at least 1 g intravenously every 8 hours to achieve trough concentrations of 15 to 20 mg/L 5
- Weight-based loading doses of vancomycin (25-30 mg/kg) are recommended in critically ill patients to achieve therapeutic concentrations rapidly 6
- Daptomycin and linezolid may be used in combination for severe MRSA infections, such as psoas abscess and bacteremia 7
Efficacy and Safety
- Linezolid has been shown to have comparable effectiveness and safety to vancomycin, teicoplanin, and daptomycin in patients with MRSA bacteremia 8
- Ceftaroline fosamil has been shown to have comparable clinical outcomes to vancomycin and daptomycin in MRSA bacteremia patients, with a lower 30-day mortality rate compared to daptomycin 4