Does vancomycin cover Methicillin-susceptible Staphylococcus aureus (MSSA) in cellulitis treatment?

From the Guidelines

Vancomycin is effective against Methicillin-susceptible Staphylococcus aureus (MSSA) in the treatment of cellulitis, but it is generally reserved for more severe infections or cases where methicillin-resistant strains (MRSA) are suspected. When treating cellulitis, vancomycin can be used to cover MSSA, especially in cases where the specific strain of Staphylococcus aureus is unknown or when MRSA is a concern 1. The typical dosing for vancomycin in adults with normal renal function is 15-20 mg/kg IV every 8-12 hours, with a duration of treatment usually ranging from 5-10 days, depending on the severity and clinical response 1. Key considerations when using vancomycin include monitoring renal function and drug levels to ensure effective and safe treatment, with therapeutic drug monitoring using trough levels typically recommended to achieve optimal dosing 1. It's also important to note that for known MSSA infections, narrower-spectrum antibiotics like cefazolin or nafcillin are often preferred as first-line treatments due to their targeted activity and lower risk of promoting antibiotic resistance 1. Some of the key points to consider when treating cellulitis with vancomycin include:

• Vancomycin's broad spectrum of activity against gram-positive organisms makes it a reliable choice when the specific strain of Staphylococcus aureus is unknown or when MRSA is a concern 1
• The importance of monitoring renal function and drug levels to ensure effective and safe treatment 1
• The recommendation to use vancomycin in combination with other antibiotics, such as piperacillin-tazobactam or imipenem-meropenem, in severely compromised patients or in cases of severe infection 1
• The general guideline to treat cellulitis for 5 days, but to extend treatment if the infection has not improved within this time period 1

From the FDA Drug Label

The comparator: vancomycin (1 g IV q12h) or an anti-staphylococcal semi-synthetic penicillin (i.e., nafcillin, oxacillin, cloxacillin, or flucloxacillin; 2 g IV q4h), each with initial low-dose gentamicin. Baseline Pathogen Methicillin-susceptible S. aureus 33/74 (45%) 34/70 (49%) −4.0% (−22.6,14.6 )‡ Among patients with persisting or relapsing S. aureus infections, 8/19 daptomycin for injection-treated patients and 7/11 comparator-treated patients died Failure of treatment due to persisting or relapsing S aureus infections was assessed by the Adjudication Committee in 19/120 (16%) daptomycin for injection-treated patients (12 with MRSA and 7 with MSSA) and 11/115 (10%) comparator-treated patients (9 with MRSA treated with vancomycin and 2 with MSSA treated with an anti-staphylococcal semi-synthetic penicillin)

Vancomycin coverage for MSSA:

• The drug label provides information on vancomycin as a comparator for treating Methicillin-susceptible S. aureus (MSSA).
• The label shows that vancomycin was used to treat MSSA with a success rate of 49%.
• However, this information is in the context of bacteremia/endocarditis, not specifically cellulitis.
• No direct information is provided about vancomycin's effectiveness in treating cellulitis caused by MSSA.
• Therefore, based on the provided label, no conclusion can be drawn about vancomycin's coverage for MSSA in cellulitis treatment 2.

From the Research

Vancomycin Coverage for Methicillin-Susceptible Staphylococcus aureus (MSSA) in Cellulitis Treatment

• Vancomycin is effective against MSSA, but its use may not always be the most appropriate choice for empiric treatment of cellulitis due to MSSA 3.
• The study by 3 found that vancomycin may be inferior to β-lactams for the empiric treatment of MSSA bacteremia, with a longer duration of bacteremia in the vancomycin group.
• Another study 4 compared the efficacy and cost of linezolid, flucloxacillin, and vancomycin in the empirical treatment of cellulitis, and found that linezolid was predicted to result in higher overall success rates and be less costly than vancomycin across the entire spectrum of patients' risk of being infected by a resistant pathogen.
• However, it is essential to note that vancomycin is still effective against MSSA, and its use may be justified in certain clinical scenarios, such as when the risk of MRSA is high or when other antibiotics are not suitable 5, 6.
• Other antibiotics, such as ceftaroline, have also shown efficacy against MSSA and may be considered as alternative treatment options 7.

Key Findings

• Vancomycin is effective against MSSA, but may not always be the best choice for empiric treatment of cellulitis due to MSSA 3.
• Linezolid may be a more effective and cost-effective option for the empirical treatment of cellulitis, especially in patients at high risk of resistant pathogens 4.
• Ceftaroline is a broad-spectrum cephalosporin with activity against MSSA and may be considered as an alternative treatment option 7.

Clinical Implications

• The choice of antibiotic for the treatment of cellulitis due to MSSA should be based on individual patient factors, such as the risk of resistant pathogens, allergy history, and renal function 5, 3.
• Vancomycin may still be a suitable option for the treatment of MSSA infections, especially in cases where other antibiotics are not effective or suitable 5, 6.