What antibiotic is effective for treating Methicillin-resistant Staphylococcus aureus (MRSA) wound infections?

From the Guidelines

For MRSA wound infections, vancomycin is typically the first-line antibiotic treatment, usually administered intravenously at 15-20 mg/kg every 8-12 hours for adults, as recommended by the Infectious Diseases Society of America 1.

Key Considerations

• Alternative options include linezolid (600 mg IV or oral twice daily), daptomycin (4-6 mg/kg IV once daily), or trimethoprim-sulfamethoxazole (1-2 double-strength tablets twice daily) for less severe infections.
• Treatment duration generally ranges from 7-14 days depending on infection severity, with longer courses needed for more serious infections.
• Wound care is essential alongside antibiotic therapy, including regular cleaning, debridement of dead tissue if necessary, and appropriate dressing changes.

MRSA Treatment Guidelines

• The Infectious Diseases Society of America recommends vancomycin, linezolid, daptomycin, telavancin, and clindamycin as treatment options for complicated skin and soft tissue infections (cSSTI) caused by MRSA 1.
• For outpatients with purulent cellulitis, empirical therapy for CA-MRSA is recommended pending culture results, with options including clindamycin, trimethoprim-sulfamethoxazole, doxycycline, and linezolid 1.

Important Notes

• MRSA requires specific antibiotics due to its resistance to standard beta-lactam antibiotics like methicillin, penicillin, and cephalosporins through the acquisition of the mecA gene, which alters the bacterial cell wall binding site that these antibiotics typically target.
• Treatment should always be guided by culture and sensitivity results whenever possible to ensure the most effective antibiotic is selected 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 Methicillin-resistant S aureus2/3 (67)0/0 (-) Methicillin-resistant S aureus12/17 (71)2/3 (67)

Antibiotic options for MRSA wound infection:

• Linezolid (PO) 2: The cure rates for MRSA skin and skin structure infection were 79% for linezolid-treated patients.
• Vancomycin (IV) 2: The cure rates for MRSA skin and skin structure infection were 73% for vancomycin-treated patients.
• Daptomycin (IV) 3: The success rates for MRSA were 44% for daptomycin-treated patients.

From the Research

Antibiotic Treatment Options for MRSA Wound Infections

• The optimal antibiotic regimen for the treatment of MRSA in surgical wounds is not known 4
• Linezolid is superior to vancomycin in the eradication of MRSA SSIs on the basis of evidence from one small trial that was at high risk of bias 4
• Other drugs, such as the new lipoglycopeptides (oritavancin, dalbavancin and telavancin) and fifth-generation cephalosporins (ceftaroline and ceftobiprole), are showing good in vitro potency and in vivo efficacy, especially for patients infected with micro-organisms with higher vancomycin minimum inhibitory concentrations (MICs) 5
• Tedizolid is an attractive agent for use both in hospital and community settings, but the post-marketing data will better clarify its potential 5
• Daptomycin and linezolid have shown non-inferiority to vancomycin in the treatment of MRSA bacteraemia and non-inferiority/superiority to vancomycin in the treatment of hospital-acquired pneumonia 5

Topical and Systemic Antibiotic Treatment

• Topical treatment with retapamulin and mupirocin is significantly more effective than systemic treatment with linezolid and vancomycin in eradicating MRSA in skin wounds 6
• Retapamulin, fusidic acid and mupirocin treatment for 3 days reduced the bacterial loads by 2.5,2.9 and 2.0 log(10) CFU, respectively, and treatment for 6 days by 5.0,4.2 and 5.1 log(10) CFU, respectively, compared with non-treated controls 6
• Systemic treatment with linezolid for 6 days reduced the bacterial loads by 1.6 log(10) CFU compared with non-treated mice, whereas vancomycin treatment showed no effect on reducing the bacterial loads in infected skin lesions 6

Vancomycin Dosing

• The standard one gram dose of vancomycin is not adequate prophylaxis for MRSA, and weight-based dosing of vancomycin at 15 mg/kg is recommended 7
• Out of 216 patients who tested positive for MRSA, 149 patients (69%) were determined to be underdosed and 22 patients (10%) patients were determined to be overdosed with the standard one gram dose of vancomycin 7
• The predicted VAN level at the end of procedure was <15 mg/L in 60% of patients with 1 gram dose compared to 12% with weight base dose 7

Tedizolid for MRSA Infections

• Tedizolid has several potential advantages over linezolid including once-daily dosing, shorter duration of therapy, and increased tolerability 8
• Tedizolid is currently being investigated for its use in other MRSA infections including nosocomial pneumonia as well as diabetic foot, bone, and joint infections and tedizolid's use in these disease states appears more promising 8