What is the most appropriate intravenous (IV) antibiotic for a diabetic patient with a plantar foot ulcer that has failed outpatient therapy?

From the Guidelines

For a diabetic patient with a plantar foot wound that has failed outpatient therapy, empiric IV antibiotic therapy should include coverage for gram-positive organisms (including MRSA), gram-negative bacteria, and anaerobes, with a recommended regimen of piperacillin-tazobactam 4.5g IV every 6-8 hours plus vancomycin dosed at 15-20 mg/kg IV every 8-12 hours. This approach is based on the guidelines from the Infectious Diseases Society of America, as outlined in the 2012 clinical practice guideline for the diagnosis and treatment of diabetic foot infections 1. The chosen regimen provides broad-spectrum coverage, addressing the polymicrobial nature of diabetic foot infections, which commonly involve Staphylococcus aureus, streptococci, enterococci, Pseudomonas, and anaerobes.

Key considerations in selecting an appropriate antibiotic regimen include:

• Coverage for MRSA, given its prevalence in severe infections or in patients with epidemiological risk factors for MRSA infection
• The need for broad-spectrum coverage, including gram-negative bacteria and anaerobes, especially in moderate to severe infections
• The importance of adjusting antibiotic doses based on renal function and monitoring levels to minimize toxicity

Alternative options, such as ertapenem 1g IV daily plus vancomycin, or meropenem 1g IV every 8 hours plus vancomycin, can also be considered, depending on the patient's specific clinical scenario and local antimicrobial resistance patterns 1.

In addition to antibiotic therapy, a comprehensive approach to managing diabetic foot infections should include:

• Surgical debridement to remove necrotic tissue
• Optimal glycemic control
• Pressure offloading
• Appropriate wound care

Duration of therapy typically ranges from 1-3 weeks, depending on clinical response, with consideration for transition to oral antibiotics once the infection shows significant improvement 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 Adult diabetic patients with clinically documented complicated skin and skin structure infections ("diabetic foot infections") were enrolled in a randomized (2:1 ratio), multi-center, open-label trial comparing study medications administered IV or orally for a total of 14 to 28 days of treatment One group of patients received ZYVOX 600 mg q12h IV or orally; the other group received ampicillin/sulbactam 1.5 to 3 g IV or amoxicillin/clavulanate 500 to 875 mg every 8 to 12 hours (q8–12h) orally. Patients in the comparator group could also be treated with vancomycin 1 g q12h IV if MRSA was isolated from the foot infection The cure rates in the ITT population, were 68.5% (165/241) in linezolid-treated patients and 64% (77/120) in comparator-treated patients

The most appropriate IV antibiotic for a diabetic patient with a plantar foot wound that failed outpatient therapy is vancomycin.

• Key points:
  • Vancomycin is effective against MRSA, which is a common cause of diabetic foot infections.
  • The cure rate for vancomycin-treated patients with diabetic foot infections was 64% in the ITT population.
  • Linezolid is also an option, with a cure rate of 68.5% in the ITT population, but vancomycin is a more traditional choice for MRSA infections 2.

From the Research

IV Antibiotic Options for Diabetic Patients with Plantar Foot Wounds

• The most appropriate IV antibiotic for a diabetic patient with a plantar foot wound that failed outpatient therapy can be determined based on the severity of the infection and the causative pathogens.
• A study comparing ertapenem and piperacillin/tazobactam for diabetic foot infections found that both antibiotics had similar efficacy and safety profiles 3.
• Ertapenem, a once-daily antibiotic, may be considered for parenteral therapy of diabetic foot infections, especially when deemed appropriate 3.
• Piperacillin/tazobactam has also been shown to be effective in treating diabetic foot infections, including those with polymicrobial infections 4.

Considerations for Antibiotic Selection

• The choice of antibiotic should be based on the severity of the infection, the presence of any underlying conditions, and the potential for antibiotic resistance.
• A study on outpatient parenteral antibiotic therapy (OPAT) for diabetic foot infections found that piperacillin/tazobactam was effective in treating infections of varying severity 4.
• The use of broad-spectrum antibiotics, including those effective against Gram-positive, Gram-negative, and anaerobic bacteria, may be necessary for the treatment of diabetic foot infections 4.

Additional Treatment Considerations

• Offloading and wound care are crucial components of the treatment of diabetic foot wounds, in addition to antibiotic therapy.
• A study on sensor-assisted wound therapy found that this approach may allow for rapid closure of plantar foot ulcers while maintaining patient mobility 5.
• Surgical interventions, such as percutaneous tendon-Achilles lengthening and proximal metatarsal osteotomy, may be necessary for the treatment of persistent or recurrent ulcers 6.