II. Pathophysiology
- Most common organisms are still aerobic Gram Positive Cocci
- Staphylococcus aureus is most common cause
- Methicillin-Resistant Staphylococcus aureus (MRSA) is present in 10-32% of diabetic infections
- Risk factors for polymicrobial infections and especially Gram Negative infections (30-40%)
- More common in Chronic Wounds or recent antibiotics
- Requires broader spectrum antibiotic use
- Risk factors for anaerobic infections
- Necrotic wounds
- Ischemic foot infections
III. Examination
- Evaluate severity of infection
- Distribution of infection
- Depth of infection
- See Probe-to-Bone Test (evaluation for Osteomyelitis)
- Associated systemic signs and symptoms
- Neurovascular examination
- Evaluate for limb ischemia (Peripheral Arterial Disease)
- Consider Ankle-Brachial Index
- Evaluate distal pulses
- Evaluate for pale or cold extremeties
- Evaluate for Diabetic Neuropathy
- Evaluate for limb ischemia (Peripheral Arterial Disease)
- Diabetic control
- Metabolic abnormalities
IV. Differential Diagnosis
- Local Trauma
- Gouty Arthritis
- Acute Charcot Neuroarthropathy
- Fracture
- Deep Venous Thrombosis
- Limb Ischemia
- Venous Stasis
V. Diagnosis: Local Infection (requires 2 classic findings of inflammation or purulence)
- Local redness, warmth, induration, swelling, pain or tenderness
- Erythema >0.5 cm around an ulcer in any direction
- Purulent drainage
- Other findings suggestive of infection
- Local wound refractory to standard therapy
- Non-purulence persistent drainage
- Malodor or friable tissue
VI. Grading: Diabetic Wound Severity (IWGDF Grade or IDSA classification)
- Grade 1: Not infected
- See diagnostic criteria above
- Grade 2: Mild infection
- Local infection of skin or subcutaneous tissue or
- Erythema around wound site measuring 0.5 to 2 cm
- Grade 3: Moderate infection
- Local infection extending deeper than subcutaneous tissue (Abscess, Osteomyelitis, Septic Arthritis or fasciitis) or
- Erythema around wound site measuring >2 cm
- Grade 4: Severe infection
- Local infection AND
- Systemic Inflammatory Response Syndrome (SIRS)
- References
VII. Labs
-
Complete Blood Count
- Leukocytosis is absent in 50% of cases of Diabetic Foot Infection
- Neutrophil Count is normal in over 80% of Diabetic Foot Infections
-
Erythrocyte Sedimentation Rate or C-Reactive Protein
- Erythrocyte Sedimentation Rate >70 mm/hour correlates with Diabetic Foot Infection
-
Wound culture
- Avoid superficial culture swabs due to inaccuracy from contamination
- Currettage from debrided ulcer base or obtain deep specimen tissue biopsy
VIII. Imaging: Suspected Osteomyelitis
- See Diabetic Foot Osteomyelitis
- XRay extremity
- See Osteomyelitis XRay
- Baseline study observing for local bone destruction, gas formation or foreign body
- Poor Test Sensitivity (as low as 25%), especially in early diabetic ulcers or mild infections (under a few weeks in duration)
- Bone Scan
- See Osteomyelitis Bone Scan
- Triple Phase Bone Scan Test Sensitivity for Osteomyelitis 90%, but Specificity is only 46%
- White Blood Cell scans increase sensitivity
- MRI (preferred)
- See Osteomyelitis MRI
- Characterizes deep infection involvement
- Detects Osteomyelitis (Test Sensitivity 90%)
IX. Management: Cellulitis in comorbid Diabetes Mellitus
- Coverage
- Early or Mild disease (2 agent protocol)
- Course: 1-2 weeks
- Agent 1: MRSA Coverage (choose one)
- Trimethoprim-Sulfamethoxazole (Septra, Bactrim) DS one to two tabs orally twice daily (preferred)
- Alternative agents in Sulfa Allergy
- Minocycline 100 mg orally twice daily
- Doxycycline 100 mg orally twice daily
- Clindamycin (risk of induced resistance)
- Agent 2: Streptococcus coverage (choose one)
- Dicloxacillin 50 mg orally four times daily or
- Cephalexin 500 mg orally four times daily or
- Penicillin VK 500 mg orally four times daily
- Severe disease (e.g. fever, systemic symptoms or signs)
- Course: 2-3 weeks with initial inpatient parenteral antibiotics
- Agent 1: Streptococcus and Enterobacteriaceae (choose one)
- Carbapenem (preferred)
- Imipenem/Cilastin (Primaxin) 500 mg IV every 6 hours (preferred) or
- Ertapenem (Invanz) 1 gram IV q24 hours or
- Doripenem 500 mg IV q8 hours or
- Meropenem 1 gram IV q8 hours
- Alternative agents
- Levofloxacin (not recommended due to growing resistance)
- Piperacillin-Tazobactam (Zosyn)
- Ticarcillin-Clavulanate (Timentin)
- Carbapenem (preferred)
- Agent 2: MRSA coverage (choose one)
- Vancomycin 30 mg/kg IV every 12 hours (first-line for MRSA)
- Daptomycin 4 mg/kg IV q24 hours or
- Linezolid 600 mg IV or PO every 12 hours or
- Tigecycline (Tygacil) 100 mg IV load and then 50 mg IV every 12 hours
X. Management: Diabetic Foot Ulcer
- See Suspected Osteomyelitis in Diabetes Mellitus
-
Wound care
- Clense and debride wounds
- Probe-to-Bone Test
- Antibiotic Course: 7-14 days for mild infections (longer course may be needed in more severe infections)
- Isolated Skin Ulcer without inflammation
- No antibiotics required
- See Diabetic Foot Ulcer for wound management
- Ulcer with superficial inflammation (2 agent protocol to cover for Streptococcus and Staphylococcus aureus)
- Agent 1: MRSA Coverage (choose one)
- Agent 2: Streptococcus coverage (choose one)
- Augmentin XR 2000/125 orally twice daily or
- Cephalexin 500 mg orally every 6 hours or
- Cefprozil 500 mg orally every 12 hours or
- Cefpodoxime 200 mg every 12 hours or
- Cefuroxime 500 mg orally every 12 hours or
- Levofloxacin 750 mg orally daily
- Ulcer with >2 cm inflammation and fascia extension (to additionally cover for Gram Negative Bacteria; risk of Osteomyelitis)
- Oral Protocol 1
- Trimethoprim-Sulfamethoxazole (Septra, Bactrim) DS one to two tabs orally twice daily AND
- Amoxicillin-Clavulanate (Augmentin) XR 2000/125 orally twice daily
- Oral Protocol 2
- Linezolid 600 mg orally twice daily AND
- Fluoroquinolone (Ciprofloxacin 750 mg twice daily or Levofloxacin 750 mg daily)
- Parenteral Protocol (2 agents)
- Agent 1: MRSA Coverage (choose 1)
- Vancomycin 30 mg/kg IV every 12 hours (first-line for MRSA) or
- Linezolid 600 mg orally twice daily or
- Daptomycin 6 mg/kg IV q24 hours
- Agent 2: Based on local susceptibilities (choose 1)
- Unasyn 3 g IV every 6 hours or
- Imipenem 0.5 g IV every 6 hours or
- Ertapenem 1 g IV every 24 hours or
- Agent 1: MRSA Coverage (choose 1)
- Oral Protocol 1
- Ulcer with extensive inflammation, deep space invasion and systemic toxicity (cover for Anaerobes, Pseudomonas)
- Agent 1: MRSA Coverage (choose 1)
- Vancomycin 30 mg/kg IV every 12 hours (first-line for MRSA) or
- Linezolid 600 mg orally twice daily or
- Daptomycin 6 mg/kg IV q24 hours
- Agent 2: Streptococcus, Anaerobe, Pseudomonas coverage
- Zosyn 3.375 g IV every 6 hours or
- Imipenem/Cilastin (Primaxin) 500 mg IV every 6 hours or
- Meropenem 1 g IV every 8 hours or
- Metronidazole 500 mg orally every 6-8 hours AND (Ciprofloxacin or Levofloxacin or Aztreonam)
- Agent 1: MRSA Coverage (choose 1)
- Other adjunctive antibiotic options
- Rifampin
- Consider as adjunctive in Diabetic Foot Osteomyelitis
- Wilson (2019) JAMA Netw Open 2(11):e1916003 +PMID:31755948 [PubMed]
- Rifampin
XI. Management: Intensive Management Indications
- Hospitalization Indications
- Moderate infection hospitalization indications
- Comorbid Peripheral Arterial Disease
- Poor glycemic control
- Unreliable patient for maintaining antibiotic regimen, wound care, off-loading and close-interval follow-up
- Severe infection or systemic infection with signs of toxicity
- Metabolic instability
- Rapidly progressive or deep infection
- Significant wound necrosis
- Gangrene
- Limb-critical ischemia
- Urgent or emergent intervention required
- Moderate infection hospitalization indications
- Surgery Indications
- Deep abscess
- Bone or joint extensively involved
- Crepitation
- Significant wound necrosis
- Gangrene
- Necrotizing Fasciitis
XII. Complications: Diabetic Foot Osteomyelitis
- See Diabetic Foot Osteomyelitis
- Epidemiology
- Present in 20% of mild to moderate Diabetic Foot Infections
- Present in up to 60% of severe Diabetic Foot Infections
- Indications to evaluate for Osteomyelitis
- Foot Ulcers >2 cm in diameter
- Foot Ulcers >3mm deep
- Foot Ulcers overlying a bony prominence
- Chronic Diabetic Foot Ulcers refractory to healing
- Probe-to-Bone Test positive (or bone visible)
XIII. Prevention
- See Diabetic Foot Care
- Avoid foot injuries
- Daily foot care and examination to catch Foot Wounds early (cuts, Blisters)
-
Foot exam at each clinic visit (socks and shoes off!)
- Assess for Diabetic Neuropathy with monofilament test (at least once yearly)
- Careful wound care
- Unload extremity of local pressure sources
- Examples: non-weight bearing, well-fitting shoes
- Keeping pressure off wound is far more important than any particular Wound Dressing choice
- Optimize glycemic control
XIV. References
- (2019) Sanford Guide, accessed on IOS 2/12/2020
- Hellekson (2005) Am Fam Physician 71:1429-33 [PubMed]
- Gemechu (2013) Am Fam Physician 88(3):177-84 [PubMed]
- Lipsky (2012) Clin Infect Dis 54(12): e132-73 [PubMed]
Images: Related links to external sites (from Bing)
Related Studies
Concepts | Disease or Syndrome (T047) |
SnomedCT | 200687002 |
English | diabetes mellitus with complication cellulitis in foot, Cellulitis in diabetic foot (diagnosis), Cellulitis in diabetic foot, Cellulitis in diabetic foot (disorder) |
Spanish | celulitis en el pie diabético (trastorno), celulitis en el pie diabético |
Ontology: Infection of foot associated with diabetes (C1642836)
Concepts | Pathologic Function (T046) |
SnomedCT | 419100001 |
Spanish | infección del pie asociada con diabetes (trastorno), infección del pie asociada con diabetes |
English | disorder of lower extremity foot infection associated with diabetes, Infection of foot associated with diabetes (diagnosis), Infection of foot associated with diabetes (disorder), Infection of foot associated with diabetes |