What is the oral (PO) coverage of Methicillin-resistant Staphylococcus aureus (MRSA)?

From the Guidelines

For MRSA infections requiring oral (PO) coverage, the first-line treatment is typically linezolid at a dose of 600mg twice daily, as recommended by the most recent guidelines 1. This recommendation is based on the latest evidence from the 2018 WSES/SIS-E consensus conference, which suggests linezolid as a first-line option for oral antibiotic coverage of MRSA in patients with skin and soft-tissue infections (SSTIs) 1. Alternatives include trimethoprim-sulfamethoxazole (TMP-SMX) at a dose of 1-2 double-strength tablets (160mg/800mg) twice daily, a tetracycline such as doxycycline 100mg twice daily, or tedizolid, as recommended by the guidelines 1. For complicated or severe infections, linezolid is often preferred but requires monitoring for myelosuppression with prolonged use. Treatment duration should be tailored to the specific infection type, with skin and soft tissue infections typically requiring 7-10 days and more invasive infections needing 14 days or longer. MRSA has developed resistance to many antibiotics, including all beta-lactams (penicillins and cephalosporins), which is why these specialized antibiotics that target different bacterial mechanisms are necessary for effective treatment. Some key points to consider when choosing an antibiotic for MRSA infections include:

• The severity of the infection
• The presence of any underlying medical conditions
• The potential for antibiotic resistance
• The need for monitoring and follow-up care It is essential to consult the latest guidelines and evidence-based recommendations when treating MRSA infections, as the most effective treatment options may change over time. In addition to antibiotic treatment, other measures such as wound care, pain management, and prevention of further infection should also be considered. Overall, the goal of treatment is to effectively manage the infection, prevent complications, and improve patient outcomes.

From the FDA Drug Label

The cure rates by pathogen for microbiologically evaluable patients are presented in Table 18. Table 18 Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Adult Patients with Complicated Skin and Skin Structure Infections Pathogen Cured ZYVOX n/N (%) Oxacillin/Dicloxacillinn/N (%) Methicillin-resistant S aureus 2/3 (67) 0/0 (-)

A separate study provided additional experience with the use of ZYVOX in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. 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

Table 19 Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Adult Patients with Diabetic Foot Infections Pathogen Cured ZYVOX n/N (%) Comparatorn/N (%) Methicillin-resistant S aureus 12/17 (71) 2/3 (67)

PO coverage of MRSA:

• The cure rates for MRSA in patients treated with linezolid were 79% in one study and 71% in another study.
• These cure rates suggest that linezolid is effective against MRSA infections.
• The dosage recommended for adult patients with MRSA infections is 600 mg q12h 2.

From the Research

PO Coverage of MRSA

• The effectiveness of various antibiotics against Methicillin-Resistant Staphylococcus aureus (MRSA) has been studied in several research papers 3, 4, 5, 6, 7.
• According to a 2014 study, linezolid is probably the drug of choice for the treatment of complicated MRSA skin and soft tissue infections (SSTIs) 3.
• A 2007 study found that vancomycin, quinupristin-dalfopristin, linezolid, tigecycline, and daptomycin are effective drugs for treating MRSA infections, with little resistance observed 4.
• A 2019 review of the evidence for trimethoprim-sulfamethoxazole (TMP-SMX), clindamycin, doxycycline, and minocycline in the treatment of MRSA pneumonia found limited data to support their use, and randomized controlled trials are required to determine their effectiveness 5.
• A 2010 study compared the use of TMP-SMX and clindamycin for community-associated MRSA (CA-MRSA) skin infections and found similar rates of treatment failure between the two antibiotics 6.
• A 2008 study evaluated the activities of clindamycin, daptomycin, doxycycline, linezolid, trimethoprim-sulfamethoxazole, and vancomycin against CA-MRSA with inducible clindamycin resistance and found that daptomycin and vancomycin demonstrated the most significant kill against all strains in both in vitro and in vivo models 7.

Antibiotic Options for MRSA

• Vancomycin: effective against MRSA, but less effective for infections with MRSA isolates that have a higher minimum inhibitory concentration (MIC) within the susceptible range 3, 4.
• Linezolid: probably the drug of choice for complicated MRSA SSTIs, but its use in pneumonia remains debatable 3.
• Clindamycin: may be used as monotherapy or in combination with other anti-MRSA antibiotics, but its activity against MRSA with inducible resistance is partially impacted by inoculum size 3, 6, 7.
• Daptomycin: non-inferior to vancomycin or β-lactams in the treatment of staphylococcal SSTIs, bacteremia, and right-sided endocarditis 3.
• Tigecycline: non-inferior to comparator drugs in the treatment of SSTIs, but its effectiveness in more serious infections is controversial 3, 4.
• Trimethoprim-sulfamethoxazole (TMP-SMX): limited data to support its use in MRSA pneumonia, and randomized controlled trials are required to determine its effectiveness 5.