What is the management plan for a diabetic patient with a 2x2 cm ulcer on the second toe, bitten by a rat 1 week ago, with bilateral inguinal lymphadenopathy (lymph node enlargement) and no history of rabies vaccination?

Management of Rat Bite with Diabetic Foot Ulcer and Lymphadenopathy

This diabetic patient requires immediate hospitalization for intravenous antibiotics, surgical debridement, wound cultures, imaging to assess for osteomyelitis, glycemic optimization, and rabies post-exposure prophylaxis given the rat bite occurred one week ago with no prior vaccination. 1, 2

Immediate Assessment and Hospitalization

Hospitalize this patient immediately given the presence of bilateral inguinal lymphadenopathy (indicating systemic spread), diabetes with likely poor glycemic control, and a moderate-to-severe infection based on ulcer size and lymph node involvement. 1 The bilateral lymphadenopathy suggests this has progressed beyond a simple local infection and warrants urgent inpatient management. 1

Critical Initial Steps

• Obtain wound cultures before antibiotics: Collect deep tissue specimens via curettage or biopsy from the debrided ulcer base, not superficial swabs, as tissue specimens provide more accurate microbiology. 1

• Blood cultures: Obtain given the systemic signs (bilateral lymphadenopathy) even without fever, as diabetic patients often lack typical inflammatory markers despite serious infection. 1

• Probe the wound: Use a sterile blunt metal probe to assess depth and determine if bone is palpable, which would indicate likely osteomyelitis. 1 Any ulcer where bone is visible or palpable has high probability of bone infection. 1

• Plain radiographs immediately: Obtain weight-bearing X-rays of the left foot to evaluate for osteomyelitis, gas in soft tissues, or foreign bodies. 1

Surgical Management

Urgent surgical consultation is mandatory for this moderate-to-severe infection with a 2x2 cm ulcer. 1

• Surgical debridement required: Remove all necrotic, infected, and non-viable tissue down to healthy bleeding tissue. 1 The wound must be thoroughly debrided before definitive cultures are obtained. 1

• Assess for deep abscess or compartment involvement: The presence of lymphadenopathy raises concern for deeper infection that may require incision and drainage. 1

• Send intraoperative tissue for culture and histopathology: If bone is encountered during debridement, send bone specimens for both aerobic/anaerobic culture and histopathology. 1

Antibiotic Therapy

Start empirical broad-spectrum intravenous antibiotics immediately after cultures are obtained. 1

Empirical Regimen

For this moderate-to-severe diabetic foot infection with systemic signs:

• Intravenous amoxicillin-clavulanate is appropriate initial therapy, as demonstrated in the case example where it successfully treated a severe diabetic foot infection. 1 This covers Staphylococcus aureus (the predominant pathogen), streptococci, and gram-negative organisms. 1

• Alternative regimens if MRSA is suspected or patient has risk factors: vancomycin plus ceftazidime (with or without metronidazole for anaerobic coverage if ischemia or gangrene present). 1

Duration and Definitive Therapy

• Continue IV antibiotics until clinical improvement: Typically 24-48 hours of clinical stability, resolution of systemic signs, and normalization of inflammatory markers. 1

• Transition to oral antibiotics: Once improved, switch to oral therapy (e.g., amoxicillin-clavulanate 875/125 mg twice daily or flucloxacillin 1g four times daily if S. aureus confirmed). 1, 3

• Total antibiotic duration:

  • 1-2 weeks for mild-moderate soft tissue infection without bone involvement. 1
  • 3 weeks for severe soft tissue infection. 1
  • 6 weeks if osteomyelitis present and bone not completely resected. 1
  • Less than 1 week if all infected bone surgically removed. 1

Rabies Post-Exposure Prophylaxis

Rabies prophylaxis is REQUIRED despite the one-week delay, as the patient has no prior rabies vaccination and rat bites can transmit rabies. 2

Specific Rabies Protocol

• Wound cleansing: Thoroughly wash and flush the wound with soap and copious water for 15 minutes (should have been done immediately but do now). 2

• Rabies Immune Globulin (RIG): Administer 20 IU/kg body weight. 2 Infiltrate the full dose around and into the wound if anatomically feasible; inject any remaining dose intramuscularly at a site distant from vaccine administration. 2

• Rabies vaccine series: Administer human diploid cell rabies vaccine (e.g., Imovax Rabies) at a different anatomical site than RIG on days 0,3,7, and 14. 2 Never administer RIG and vaccine in the same syringe or same site. 2

• Tetanus prophylaxis: Update tetanus immunization as indicated. 2

Glycemic Control and Metabolic Optimization

Optimize blood glucose immediately as hyperglycemia impairs neutrophil function and wound healing. 1

• Insulin therapy: Start or intensify insulin regimen (long-acting plus correctional short-acting subcutaneous insulin). 1

• Target glucose control: Aim for blood glucose <180 mg/dL during acute infection, though perfect control should not delay discharge. 1

• Monitor for diabetic ketoacidosis: Check electrolytes, renal function, and consider arterial blood gas if metabolically unstable. 1

Vascular Assessment

Evaluate arterial perfusion as peripheral vascular disease significantly impacts healing and infection outcomes. 1

• Palpate pulses: Document dorsalis pedis and posterior tibial pulses bilaterally. 1

• Ankle-brachial index (ABI) and toe pressures: If pulses diminished or absent, obtain ABI and toe-brachial index (TBI should be >0.7). 1

• Arterial duplex ultrasound: If ischemia suspected (absent pulses, abnormal TBI), obtain vascular imaging to assess for significant stenosis requiring revascularization. 1

Wound Care and Off-Loading

Strict off-loading is essential to prevent further trauma and promote healing. 1

• Total contact cast or removable knee-high offloading device: Once infection controlled and no need for frequent wound inspection, prescribe appropriate off-loading (e.g., DH Offloading Walker). 1

• Daily wound inspection initially: During active infection, wounds need daily assessment, making total contact casts inappropriate. 1

• Dressing selection: No specific dressing type has proven superior; use simple gauze or moisture-appropriate dressings changed at least daily. 1

Monitoring and Follow-Up

Re-evaluate within 3-5 days (or sooner if worsening) to assess response to therapy. 1

• Clinical improvement markers: Decreasing erythema, edema, purulent drainage; resolution of fever and lymphadenopathy; improving wound appearance. 1

• Laboratory monitoring: Expect decreasing white blood cell count and C-reactive protein, though these are not required for routine monitoring. 1

• If not improving: Reassess for undiagnosed osteomyelitis (obtain MRI if X-ray negative but clinical suspicion high), deep abscess, antibiotic resistance, or critical ischemia. 1

Common Pitfalls to Avoid

• Do NOT delay rabies prophylaxis: Even at one week post-bite, rabies prophylaxis is still indicated and potentially life-saving. 2

• Do NOT use superficial wound swabs: These yield inaccurate microbiology with more contaminants and fewer true pathogens. 1

• Do NOT give antibiotics for longer than infection persists: Antibiotics treat infection, not open wounds; discontinue when signs of infection resolve even if wound not healed. 1

• Do NOT exceed recommended RIG dose: Excessive rabies immune globulin may suppress active antibody production. 2

• Do NOT assume absence of fever means mild infection: Diabetic patients with severe infections often lack typical inflammatory signs. 1