Standard, Appropriate, and Advanced Care and Medical-Legal Considerations: Part One -- Diabetic Foot Ulcerations

Gerit Mulder, DPM, MS, David Armstrong, DPM, Susie Seaman, MSN, NP, CETN

Disclosures

Wounds. 2003;15(4) 

In This Article

Infection Control

The single most frequent cause of amputation in the diabetic foot is the diabetic wound, which becomes the portal of bacterial entry, colonization, and subsequent infection.[18,31] While it is beyond the scope of this paper to discuss management of infection, various measures may be taken to reduce the risks and complications of colonization.

Diabetic ulcers are at high risk of infection secondary to impaired leukocyte chemotaxis and phagocytosis. High glucose levels and poor tissue perfusion may compound this condition. Decreased ability to fight off infection combined with tissue hypoxia creates an ideal environment for a necrotizing infection.[10,45]

Limb-threatening diabetic infections are usually polymicrobial involving multiple aerobic and anaerobic infections. Staphylococcus aureus, beta-hemolytic streptococcus, Enterobacteriaceae, Bacteroides fragilis, Peptococcus, and Peptostreptococcus may be cultured from diabetic ulcers. Malodorous wounds are likely to harbor aerobic and anaerobic organisms.[31]

Choice of antimicrobials in the treatment of a limb-threatening diabetic foot ulcer infection should include those with activity against Gram-positive and Gram-negative organisms and provide aerobic and anaerobic coverage. The patient's overall wound and medical status as well as the patient's medical history determine the choice of oral versus intravenous antibiotics and the need for hospitalization. Clinicians may not have the luxury of awaiting culture or biopsy results prior to determining antibiotic choice. Treatment may be changed when dictated by the culture result or when the patient is not responding to treatment. Cultures are most reliable when a deep tissue specimen is obtained.[32] All organisms recovered from deep tissue cultures should be treated as pathogens unless there is evidence to support that the culture was contaminated from another source. Swab cultures usually grow out numerous surface contaminants and may not provide information on the pathogen(s) causing the deep tissue infection. The rapid deterioration of an infected wound in the diabetic patient necessitates immediate action by a clinician to prevent amputation and other complications.

Topical antibiotics and antimicrobials are not indicated for the treatment of a deep tissue or bone infection. Topical agents may reduce colonization in the wound, thereby reducing the risk of infection. Topical antimicrobials have neither been proven to eradicate an infection nor to be effective in the treatment of an infection. The primary line of therapy for infection is the use of oral or systemic antibiotics. It is the responsibility of the clinician to differentiate between contamination (the presence of organisms in a wound), colonization (the multiplication of organisms), and infection (the presence of greater than 1 x 105 organisms per gram of tissue).[45] Diagnosis of an infection should be based on clinical findings. Cultures are meant to identify organisms and to assist in treatment of an infection rather than be used to diagnose infection. Antibiotics are known to be used indiscriminately and without need resulting in an increased probability of developing resistance.[46,47] The high morbidity and mortality associated with infected diabetic ulcers suggest that the prescription antibiotics may be more appropriate when clinical signs of infection are suspected in a diabetic ulcer than in wounds of other etiologies, with the exception of immunocompromised patients.

Bone detected by probing a pedal ulcer has a sensitivity of 66 percent for osteomyelitis and a specificity of 85 percent.[29] Determining the presence of osteomyelitis may prove difficult when Charcot disease is co-existent.[32] While standard radiographs may be of assistance in diagnosing osteomyelitis, MRI is considered the more sensitive and specific pathologic confirmation of osteomyelitis. Serial radiographs compared with baseline radiographs may be of significant value in determining progressive bone changes resulting from osteomyelitis. Clinicians are advised to use clinical findings and judgment in conjunction with all available test results, including but not limited to radiographs, MRI, and scans, prior to determining the presence of osteomyelitis. Appropriate care may include surgical intervention, bone debridement, infectious disease consultation, extended antibiotic therapy, and hospitalization. In patients with osteomyelitis that has been present for extended periods of time without complications, recurrent ulcerations, or significant progression, the clinician may decide to defer aggressive intervention.

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