Diabetic Foot Infections

Causative Pathogens

• Beta-hemolytic streptococci and Staphylococcus aureus are common causes of cellulitis without an open wound, while S. aureus and beta-hemolytic streptococci are common causes of infected ulcers in antibiotic-naïve patients 1
• S. aureus, beta-hemolytic streptococci, and Enterobacteriaceae are common causes of chronic or previously treated infected ulcers, and Pseudomonas aeruginosa is a common cause of macerated wounds due to soaking 1
• Aerobic gram-positive cocci, diphtheroids, Enterobacteriaceae, Pseudomonas species, nonfermentative gram-negative rods, and possibly fungi are common causes of long-duration nonhealing wounds with prolonged antibiotic therapy 1
• Mixed aerobic gram-positive cocci, Enterobacteriaceae, nonfermentative gram-negative rods, and obligate anaerobes are common causes of "fetid foot" with extensive necrosis/gangrene 1
• The clinical presentation of diabetic foot infections can be categorized based on the predominant pathogens, as shown in the following table:

Risk Factors and Complications

• Peripheral neuropathy, vascular insufficiency, and immunological dysfunction are risk factors for diabetic foot infections, which can lead to skin breaks, impaired tissue viability, and compromised defense against pathogens 1, 3
• Skin barrier disruption, such as autonomic neuropathy leading to dry, cracking skin, creates entry points for bacteria, and chronic wounds are characterized by hyperglycemia-induced advanced glycation end products, persistent inflammation, and apoptosis 1, 3
• Systemic symptoms may be minimal even in severe infections, leading to underestimation of severity, and failure to address predisposing factors can lead to recurrence 3, 4
• Prior hospitalization, surgical procedures, prolonged or broad-spectrum antibiotic therapy, and chronic wounds are risk factors for the development of resistant organisms in diabetic foot infections 1
• Diabetic patients are at higher risk of developing complicated abscesses due to concomitant chronic renal failure, and abscesses can present atypically with less evident systemic symptoms due to altered immune response 3, 1

Diagnosis and Evaluation

• Evaluation should include a detailed physical examination, deep tissue cultures, and imaging studies such as ultrasound or computed tomography to detect deep abscesses, as recommended by the Infectious Diseases Society of America and the American College of Radiology 1
• Early evaluation of any skin lesion or infection is crucial to prevent progression and improve outcomes, according to the Infectious Diseases Society of America 5

Treatment and Management

• For uncomplicated cellulitis in diabetics, antibiotics should primarily target streptococci, and many clinicians also choose agents effective against S. aureus as a precaution, especially in diabetic patients 4
• Empirical initial antibiotic therapy should cover Staphylococcus aureus (including MRSA if locally prevalent) and consider coverage for gram-negative organisms in moderate to severe infections, according to the Infectious Diseases Society of America 3
• The duration of antibiotic treatment should be 1-2 weeks for mild to moderate infections and longer for severe or complicated infections, as recommended by the American Diabetes Association 3
• Treatment of tinea pedis is important in preventing recurrent cellulitis, and patients with diabetes who respond slowly to therapy may have deeper infections requiring more aggressive management 4, 3
• Maintaining optimal glycemic control can improve immune function and prevent complications in diabetic patients, as noted by the American Diabetes Association 5
• Multidisciplinary care, including infectious disease specialists when possible, is essential for optimal management, as recommended by the American Diabetes Association 5
• The management of abscesses in diabetic patients requires urgent surgical intervention in cases of deep abscesses, compartment syndrome, and nearly all necrotizing soft tissue infections, as well as consideration for surgical intervention in cases of osteomyelitis accompanied by spreading soft tissue infection 3
• Strict glycemic control is a fundamental part of treatment for diabetic patients with abscesses, as recommended by the American Diabetes Association 3