Diabetes-Related Foot Infections: Diagnosis and Treatment

 

Am Fam Physician. 2021 Oct ;104(4):386-394.

  Patient information: See related handout on preventing diabetic foot infections.

Author disclosure: No relevant financial affiliations.

Diabetes-related foot infections occur in approximately 40% of diabetes-related foot ulcers and cause significant morbidity. Clinicians should consider patient risk factors (e.g., presence of foot ulcers greater than 2 cm, uncontrolled diabetes mellitus, poor vascular perfusion, comorbid illness) when evaluating for a foot infection or osteomyelitis. Indicators of infection include erythema, induration, tenderness, warmth, and drainage. Superficial wound cultures should be avoided because of the high rate of contaminants. Deep cultures obtained through aseptic procedures (e.g., incision and drainage, debridement, bone culture) help guide treatment. Plain radiography is used for initial imaging if osteomyelitis is suspected; however, magnetic resonance imaging or computed tomography may help if radiography is inconclusive, the extent of infection is unknown, or if the infection orientation needs to be determined to help in surgical planning. Staphylococcus aureus and Streptococcus agalactiae are the most commonly isolated pathogens, although polymicrobial infections are common. Antibiotic therapy should cover commonly isolated organisms and reflect local resistance patterns, patient preference, and the severity of the foot infection. Mild and some moderate infections may be treated with oral antibiotics. Severe infections require intravenous antibiotics. Treatment duration is typically one to two weeks and is longer for slowly resolving infections or osteomyelitis. Severe or persistent infections may require surgery and specialized team-based wound care. Although widely recommended, there is little evidence on the effectiveness of primary prevention strategies. Systematic assessment, counseling, and comorbidity management are hallmarks of effective secondary prevention for diabetes-related foot infections.

Diabetes-related foot infections form in approximately 40% of foot ulcers in patients with diabetes mellitus.1 Infections can rapidly progress to cellulitis, abscess formation, osteomyelitis, and necrotizing fasciitis. In 2016, diabetes-related foot infections contributed to more than 130,000 lower-extremity amputations in the United States.2 The five-year mortality rate following amputation is approximately 50%, exceeding the mortality rate of many cancers.3

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingComments

Routine superficial wound cultures should not be performed because the results have poor sensitivity and specificity for identifying a pathogenic organism compared with deep tissue cultures.6,12

B

Systematic review and meta-analysis of lower quality diagnostic cohort studies

Initial testing in patients with diabetes mellitus and suspected osteomyelitis should include plain radiography, a C-reactive protein test, and probe-to-bone testing.6,11,15

B

Lower quality diagnostic cohort studies

Empiric antibiotic therapy should target Streptococcus agalactiae and Staphylococcus aureus; however, additional coverage should be considered based on local antimicrobial sensitivities, the severity of infection, and patient factors.69

C

Consensus guidelines and inconsistent diagnostic cohort studies

Antibiotic coverage for methicillin-resistant S. aureus may be discontinued in a patient with a diabetes-related foot infection and a negative methicillin-resistant S. aureus nares culture considering the high negative predictive value of this test.13,14

B

Lower quality diagnostic cohort studies

Secondary prevention of a foot infection in a patient with diabetes should include systematic foot assessment, foot care counseling, use of appropriate footwear, and comorbidity management.4244

B

Systematic review of lower quality clinical trials and studies with inconsistent findings


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

The Authors

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ERIC M. MATHESON, MD, MS, is the transitional year residency director and associate professor in the Department of Family Medicine at the Medical University of South Carolina, Charleston....

SCOTT W. BRAGG, PharmD, BCPS, is an associate professor in the Department of Family Medicine and the Department of Clinical Pharmacy and Outcomes Sciences at the Medical University of South Carolina.

RUSSELL S. BLACKWELDER, MD, MDiv, CMD, is the director of Geriatric Education and assistant professor in the Department of Family Medicine at the Medical University of South Carolina.

Address correspondence to Eric M. Matheson, MD, MS, 9228 Medical Plaza Dr., Charleston, SC 29406 (email: matheson@musc.edu). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


Data Sources: A PubMed search was completed in Clinical Queries using the key terms diabetic foot ulcers, infections, antibiotics, statistics, pharmacological, and prevention. The search included meta-analyses, randomized controlled trials, clinical trials, and reviews. Also searched were Access Medicine, the Cochrane Library, Lexicomp, the National Guideline Clearing-house database, and UpToDate. Search dates: October 27, 2020 to November 4, 2020, and April 26, 2021.

Figure 1 and Figure 2 provided courtesy of Joshua Visserman, MD.

References

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