Diabetic Foot Infections Treatment & Management

Cellulitis is the easiest diabetic foot infection to cure, because it does not pose the same circulatory limitations that the more serious infections do, making it easier for medications to reach the infection site. In contrast, chronic osteomyelitis, which is the most difficult diabetic foot infection to cure, requires surgical debridement before antibiotic therapy can be effective. The patient may participate in activities as tolerated. However, weight bearing may be contraindicated. Glycemic control must be achieved to favorably affect outcome; it is important for microbial eradication and tissue healing. 

Collaborative clinical practice guidelines for treating diabetic foot have been published by the Society for Vascular Surgery, the American Podiatric Medical Association, and the Society for Vascular Medicine. ^[15] Guideline developers highlighted the strong evidence for total contact casting in the treatment of plantar diabetic foot ulcers, which they indicated was not a new treatment, but one that is underutilized. Other important aspects in the guidelines are as follows:

• Help in identifying high-risk patients
• Periodic updates required based on the emergence of new evidence
• Identification of, grading of, and protocols for various wound care treatments in diabetic foot
• Implementation of guidelines into training programs

A literature review by Matos et al suggested that exercise and physical activity are effective against the complications of diabetic foot. The investigators found that patients involved in physical activity and exercise had a lower annual incidence of ulcers than other patients in the study (0.02 vs 0.12, respectively). Moreover, nerve velocity conduction, peripheral sensory function, and foot peak pressure distribution significantly improved in the physical activity/exercise group. ^[16]

A prospective observational study by Hwang et al indicated that treatment with allogeneic keratinocyte dressings is effective in patients with chronic, intractable diabetic foot ulcers. Of the 71 patients in the study, all of whom underwent weekly keratinocyte therapy, 56 (78.9%) experienced complete wound healing, including 46 (64.8%) in whom complete healing occurred within an average of 6.1 weeks. ^[17]

Go to Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Foot; and Diabetic Ulcers to see more complete information on these topics.

Guidelines

The aforementioned 2019 update to evidenced-based guidelines by the International Working Group on the Diabetic Foot (IWGDF) included the following recommendations with regard to the treatment of diabetic foot infection ^[14] :

• A patient with a diabetic foot infection should be treated with an antibiotic agent whose efficacy has been demonstrated in a published randomized, controlled trial and that is appropriate for the specific individual; among the agents to consider are penicillins, cephalosporins, carbapenems, metronidazole (in combination with one or more other antibiotics), clindamycin, linezolid, daptomycin, fluoroquinolones, and vancomycin; tigecycline should not be considered
• Factors that should be taken into account in the selection of an antibiotic agent for the treatment of a diabetic foot infection include the following: the likely or proven causative pathogen(s) and their antibiotic susceptibilities; the infection’s clinical severity; published evidence of the agent’s efficacy against diabetic foot infections; risk of collateral damage to the commensal flora and other adverse events; drug interaction risk; agent availability; and cost
• Patients with a skin or soft tissue diabetic foot infection should undergo 1-2 weeks of antibiotic therapy
• When no other indication for surgery exists, consider managing a patient with diabetes and uncomplicated forefoot osteomyelitis via antibiotic therapy, with no bone resection
• Urgent evaluation is necessary with regard to the need for surgery, as well as intensive postoperative medical and surgical follow-up, when probable diabetic foot osteomyelitis exists with concomitant soft tissue infection
• Patients with diabetic foot osteomyelitis should undergo antibiotic therapy for no more than 6 weeks; failure to see clinical improvement of the infection within the first 2-4 weeks should prompt reconsideration of bone specimen collection (for culture), surgical resection, or selection of an alternative antibiotic regimen
• If one or more pathogens grow from an aseptically collected culture specimen obtained during bone resection surgery for diabetic foot osteomyelitis, or if osteomyelitis is revealed histologically, appropriate antibiotic treatment should be administered for up to 6 weeks

A 9-member panel of podiatrists, surgeons, and other experts in diabetic foot care provided the following new guidelines based on the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system: ^{[18, 19]}

• Vascular management, infection management and prevention, and pressure relief are essential to diabetic foot ulcer healing. Often denoted in the wound-care literature as VIP, this is the overall aggressive approach the panel deems necessary for foot ulcer healing.

• Vascular assessment requires a combination of physical examination and laboratory tests. Blood pressure indices such as the ankle-brachial index have poor reliability in patients with diabetes, so they should not be used as the only assessment.

• For infection diagnosis and treatment, the panel endorses the clinical practice guidelines of the Infectious Diseases Society of America.

• Adequate offloading increases the likelihood of diabetic foot ulcer healing. Several studies suggest that offloading facilitates healing by reducing both pressure on the foot and strain rate.

• For guidance on offloading the Charcot foot, the panel endorses the Charcot Foot in Diabetes Consensus Report. ^[20]

• Total contact casting is the preferred method for offloading plantar diabetic foot ulcers because it has most consistently demonstrated the best healing outcomes and is a cost-effective treatment.

• Advanced therapeutics are unlikely to succeed in improving wound-healing outcomes unless effective offloading is achieved.

• Several studies support the use of advanced therapies, such as cellular or tissue-based wound-healing products, as adjunctive wound care treatments, but only if offloading is also achieved.

Infections in patients with diabetes are difficult to treat because these patients have impaired microvascular circulation, which limits the access of phagocytic cells to the infected area and results in a poor concentration of antibiotics in the infected tissues. For this reason, cellulitis is the most easily treatable and reversible form of foot infections in patients with diabetes. Deep-skin and soft-tissue infections are also usually curable, but they can be life threatening and result in substantial long-term morbidity. ^{[3, 4, 5, 6, 7]}

For specific information concerning the evaluation and management of diabetic foot infections, including choices of antimicrobial agents, the reader is referred to authoritative guidelines published by the Infectious Diseases Society of America. ^[21]

If infection is suspected, the choice of antibiotics should be based on type/severity of the infection and the likelihood that resistant organisms are involved. Ideally, antibiotics should be chosen based on culture and sensitivity data, but these are not always available. Because data are limited, it is often difficult to compare treatment regimens for efficacy.

Patients with mild infections can be treated in outpatient settings with oral antibiotics that cover skin flora including streptococci and Staphylococcus aureus. Agents such as cephalexin, dicloxacillin, amoxicillin-clavulanate, or clindamycin are effective choices. If methicillin-resistant S aureus (MRSA) infection is suspected, then clindamycin, trimethoprim-sulfamethoxazole, minocycline, or linezolid may be used. If gram-negative aerobes and/or anaerobes are suspected, dual drug treatment with trimethoprim-sulfamethoxazole plus amoxicillin-clavulanate or clindamycin plus a fluoroquinolone such as levofloxacin or moxifloxacin may be used.

For moderate-to-severe infections, patients should be hospitalized for parenteral antibiotic therapy. Empiric choices should cover streptococci, MRSA, aerobic gram-negative bacilli, and anaerobes. MRSA is covered by vancomycin, linezolid, or daptomycin. Acceptable choices for gram-negative aerobic organisms and anaerobes include ampicillin-sulbactam, piperacillin-tazobactam, meropenem, or ertapenem. Alternatively, ceftriaxone, cefepime, levofloxacin, moxifloxacin, or aztreonam plus metronidazole would be sufficient to cover aerobic gram-negative and anaerobic organisms. Tigecycline has been studied, but published experience is limited.

Duration of therapy should be individualized. For those treated in outpatient settings with oral antibiotics, duration of treatment is usually 7-14 days. In those treated parenterally but without osteomyelitis, 2-4 weeks is sufficient.

In patients with diabetic foot osteomyelitis, a 6-week course of antibiotics may be sufficient even in the absence of surgery, according to a randomized prospective study of 40 French patients. Current guidelines recommend at least 3 months or more of antibiotic therapy when diabetic foot osteomyelitis is not treated surgically or when residual dead bone remains after surgery. In the study, however, remission occurred in 12 patients (60%) treated for 6 weeks and in 14 patients (70%) treated for 12 weeks (P = 0.50). ^{[22, 23]}

Antibiotics were administered orally for the entire treatment period or intravenously for 5 to 7 days and then orally. Remission was defined as complete and sustained healing of the wound, if present; absence of recurrent infection; and no need for surgical intervention by at least 1 year months after completion of antibiotic treatment. Antibiotic-related adverse events were observed in six (30%) of the patients in the 6-week-treatment group and 10 (50%) of the patients in the 12-week treatment group. ^{[22, 23]}

Duration of treatment may be shortened in those patients who undergo amputation as part of the treatment regimen. Consultation with an infectious diseases expert is recommended.

In terms of the infecting microorganisms and the likelihood of successful treatment with antimicrobial therapy, acute osteomyelitis in patients with diabetes is essentially the same as in those without diabetes.

As previously mentioned, in chronic osteomyelitis, a sequestrum and involucrum form; these represent islands of infected bone. Bone fragments that are isolated have no blood supply; systemic antibiotics do not penetrate these devascularized, infected bone fragments. Therefore, antibiotic therapy alone cannot cure patients with chronic osteomyelitis.

Adequate surgical debridement, in addition to antimicrobial therapy, is necessary to cure chronic osteomyelitis. Immobilization is important in acute or chronic osteomyelitis.

Dry gangrene is usually managed with expectant care, and gross infection is usually not present. Wet gangrene usually has an infectious component and requires surgical debridement and/or antimicrobial therapy to control the infection.

Surgical debridement in diabetic patients with chronic osteomyelitis is the most important therapeutic intervention, as this condition cannot be cured without it. This is because debridement removes the infected, bony fragments that antibiotics cannot reach so that affected areas can be treated with antimicrobial therapy; in some cases, amputation is required. Patients who have fetid foot require extensive surgical debridement and/or amputation. If amputation is performed, physical therapy and rehabilitation may be started on an inpatient basis and completed on an outpatient basis.

Appropriate consultation with a surgeon should be obtained for debridement and/or amputation in chronic osteomyelitis, as well as for debridement or decompression of compartment syndromes in patients with deep-skin and soft-tissue infections. In addition, a vascular surgical evaluation to bypass large-vessel occlusive disease should be considered in patients with diabetic foot infections and peripheral vascular disease. Note, however, that large-vessel bypass does not cure the microvascular component of diabetic foot infections.

An infectious disease specialist should be consulted in the treatment of all patients with diabetic foot infections to optimize the antimicrobial therapy.

Cellulitis

No further care is necessary.

Skin and soft-tissue infection

Additional debridement is generally indicated. The best care plan is aggressive therapy to avoid surgery beyond transmetatarsal amputation (ie, limit surgical extirpation to the forefoot).

Acute osteomyelitis

Monitor the patient's condition to ensure that the infection has resolved.

Chronic osteomyelitis

Ensure that debridement is complete and that no further remnants of infected bone remain.