From the Guidelines
Yes, you should routinely cover anaerobes in diabetic foot infections. Empiric antibiotic therapy for diabetic foot infections should include coverage for both aerobic and anaerobic organisms since these infections are typically polymicrobial, as noted in the 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections 1. For mild to moderate infections, oral options include amoxicillin-clavulanate (875/125 mg twice daily), clindamycin (300-450 mg four times daily), or the combination of metronidazole (500 mg three times daily) with a fluoroquinolone like ciprofloxacin (500-750 mg twice daily).
Key Considerations
- The environment of diabetic foot wounds is often hypoxic, creating ideal conditions for anaerobes like Bacteroides, Peptostreptococcus, and Clostridium species, which contribute significantly to tissue destruction and can lead to complications like gangrene if not adequately treated.
- Proper wound care, debridement of necrotic tissue, and offloading pressure from the wound are critical adjunctive measures to antibiotic therapy.
- Treatment duration typically ranges from 1-2 weeks for mild infections to 2-3 weeks for moderate to severe infections.
Treatment Options
- For severe infections requiring intravenous therapy, options include piperacillin-tazobactam (3.375-4.5 g every 6-8 hours), ertapenem (1 g daily), or a combination of vancomycin (15-20 mg/kg every 8-12 hours) plus either metronidazole (500 mg every 8 hours) or a carbapenem, as suggested by the guidelines 1.
- The choice of antibiotic should be guided by the severity of the infection, the presence of antibiotic-resistant organisms, and the results of aerobic and anaerobic cultures, if available.
From the Research
Diabetic Foot Infections and Anaerobes
- Diabetic foot infections (DFIs) are polymicrobial, involving a complex community of bacteria, including anaerobes 2.
- The presence of anaerobes in DFIs is more commonly detected using molecular techniques such as 16S rRNA gene sequencing, with a weighted average of 83.8% of patients having anaerobes, compared to 17% detected by culture 2.
- Anaerobes are more frequently found in deeper or more chronic wounds, and their detection is associated with fever, malodorous lesions, and ulcer depth and duration 2, 3.
Treatment of Diabetic Foot Infections
- Empiric antibiotic therapy for DFIs is generally broad-spectrum and usually has activity against the most frequently identified anaerobes, such as Peptostreptococcus and Bacteroides species 3.
- Adequate surgical debridement and, when needed, foot revascularization may be at least as important as the choice of antibiotic to achieve a successful treatment outcome 3.
- The use of broad-spectrum antibiotics such as moxifloxacin, which has activity against anaerobes, may be effective in treating moderate-to-severe DFIs 4.
Role of Anaerobes in Diabetic Foot Infections
- The role of anaerobes in DFIs is not fully understood, and it remains unclear whether their presence leads to more severe manifestations or if they are largely colonizers associated with tissue ischemia and necrosis 3.
- However, the high rate of patients with DFIs involving anaerobes, and the increased knowledge on the species identified, their virulence factors, and their potential role in wound evolution, support recommendations combining debridement and antibiotic therapy effective on anaerobes in moderate and severe DFIs 2.