How should a rat bite be managed, including wound care, tetanus prophylaxis, and appropriate antibiotic therapy?

Management of Rat Bite Wounds

Rat bites should be managed with thorough wound irrigation, tetanus prophylaxis if indicated, and consideration of prophylactic antibiotics for high-risk wounds, particularly deep puncture wounds which carry significant infection risk from polymicrobial flora including Staphylococcus aureus and anaerobes. 1, 2

Immediate Wound Care

• Irrigate the wound copiously with sterile normal saline or running tap water until all visible debris is removed, using mechanical pressure to flush out bacteria 1, 3
• Perform gentle debridement of only superficial debris and any devitalized tissue, avoiding aggressive manipulation that could drive bacteria deeper 3, 4
• Do not close rat bite wounds with sutures—these puncture wounds should heal by secondary intention to allow drainage and prevent trapping bacteria 1
• Facial wounds are the only exception and may be closed primarily after meticulous irrigation and with prophylactic antibiotics 1

Tetanus Prophylaxis

Administer tetanus toxoid if the patient has not received vaccination within the past 10 years for clean wounds, or within 5 years for contaminated wounds (which rat bites are). 1

• Tdap (tetanus, diphtheria, pertussis) is preferred over Td if the patient has not previously received Tdap 1
• If immunization history is unknown or incomplete, treat as unvaccinated: give both tetanus toxoid and tetanus immune globulin (TIG) at separate sites 1, 3
• Patients with complete primary series who received their last dose >5 years ago should receive a booster 1

Antibiotic Therapy

Indications for Prophylactic Antibiotics

Given the deep puncturing nature of rodent bites and polymicrobial flora, prophylactic antibiotics should be strongly considered, particularly for: 2

• Deep puncture wounds (most rat bites fall into this category) 2, 4
• Wounds involving the hand, face, feet, or near joints 1, 3
• Immunocompromised patients or those with prosthetic devices 1, 3
• Wounds with signs of infection (Type II or III injuries with ulceration or tissue loss) 4

Antibiotic Selection

Amoxicillin-clavulanate is the first-line oral antibiotic for rat bite wounds, providing coverage for the broad range of aerobic and anaerobic bacteria including Staphylococcus aureus (the most common isolate), streptococci, and anaerobes 1, 3, 2

• Adult dosing: Amoxicillin-clavulanate 875-125 mg orally twice daily 1
• Duration: 3-5 days for prophylaxis; 7-10 days if infection is present 1, 3

Alternative Regimens (for penicillin allergy):

• Moxifloxacin alone (covers both aerobes and anaerobes) 1
• Ciprofloxacin or levofloxacin PLUS metronidazole (to ensure anaerobic coverage) 1
• Doxycycline may be used but should be combined with metronidazole for anaerobic coverage 3

Avoid monotherapy with first-generation cephalosporins, macrolides, or clindamycin alone—these lack adequate coverage for the polymicrobial flora of rat bites 3, 2

Special Considerations

Rat Bite Fever (Streptobacillus moniliformis)

• This serious complication presents 5-10 days post-bite with fever, rash, myalgia, and potentially septic arthritis 5, 6
• Penicillin is the treatment of choice; tetracycline is an alternative for penicillin-allergic patients 5, 6
• Diagnosis requires blood culture or wound culture, though the organism is fastidious and difficult to grow 5, 6
• Complications can include endocarditis and osteomyelitis if untreated 6

Wound Classification and Management

Research suggests three types of rat bite wounds: 4

• Type I (superficial scratches): Conservative wound care, typically no antibiotics or admission needed 4
• Type II (deeper bites with infection/ulceration): May require drainage and debridement; antibiotics indicated 4
• Type III (full-thickness with tissue loss): May require skin grafting; antibiotics and surgical consultation 4

Follow-up and Monitoring

• Arrange follow-up within 24 hours (phone or office visit) to assess for early infection signs 3
• Instruct patients to return immediately for increasing pain, redness, swelling, warmth, fever, or systemic symptoms 3
• Elevate the injured extremity to reduce edema and promote healing 3

Critical Pitfalls to Avoid

• Do not underestimate infection risk—rat bites are polymicrobial with approximately 72.5% of infections involving multiple organisms 2
• Do not delay initial evaluation—early intervention prevents serious complications including septic arthritis and osteomyelitis 3, 6
• Do not close puncture wounds—this traps bacteria and dramatically increases infection risk 1
• Do not use inadequate antibiotic coverage—ensure both aerobic and anaerobic coverage given the polymicrobial nature 1, 2
• Do not forget tetanus prophylaxis—rat bites are contaminated wounds requiring assessment of immunization status 1