👊Human Bite (“Fight Bite”) to the Hand

Scenario
A 28‑year‑old man presents to the ED 12 hours after punching another person in the face and sustaining a 1 cm laceration over the dorsal aspect of his right third metacarpophalangeal joint. He cleaned it at home but now has:

• Increasing pain, swelling, and erythema over the joint

• Temperature 38.2 °C, pulse 100 bpm

• Mild crepitus when extending the finger

• No obvious abscess, but the wound is tender with a small serosanguineous discharge

He is otherwise healthy, with no penicillin allergy.

---

Question

Which empiric oral antibiotic regimen is most appropriate for this patient?

A) Amoxicillin–clavulanate
B) Clindamycin monotherapy
C) Doxycycline + metronidazole
D) Cephalexin
E) Dicloxacillin

✅ Correct Answer: A) Amoxicillin–Clavulanate

---

📘 Mini‑Lesson & Teaching Points

            Likely Pathogens:

• Eikenella corrodens (Gram‑negative), oral anaerobes

• Staphylococcus aureus, Streptococcus spp.

• Note: Pasteurella multocida (from cat bites) can mimic Eikenella corrodens in terms of rapid onset cellulitis and similar antibiotic susceptibilities, but human‐bite wounds classically involve Eikenella.

1. Why Amoxicillin–Clavulanate?

   • Single‑agent cover for Eikenella and anaerobes, plus Staph/Strep

   • Excellent oral bioavailability; standard first‑line for human‐bite wounds

2. Why the Others Are Less Suitable

   • B) Clindamycin: No reliable Gram‑negative/Eikenella coverage

   • C) Doxycycline + Metronidazole: Covers Eikenella and anaerobes—acceptable second‐line if β‑lactam allergy, but two drugs vs one

   • D) Cephalexin: Good for MSSA/Strep only; misses Gram‑negatives/anaerobes

   • E) Dicloxacillin: Narrow anti‑staph agent; no Gram‑negative or anaerobic activity

3. Alternative for Penicillin Allergy

   • Doxycycline + metronidazole or moxifloxacin monotherapy are guideline‑endorsed alternatives in true β‑lactam allergy 

4. Additional Management

   • I&D or joint washout if septic arthritis is suspected (crepitus, painful ROM)

   • Tetanus prophylaxis and update immunisation if needed

   • Leave the wound open—do not suture human‐bite wounds due to high infection risk

---

Key Take‑Home:
For uncomplicated human‐bite cellulitis in a non‐allergic patient, amoxicillin–clavulanate is the empiric oral antibiotic of choice. In those with penicillin allergy, switch to doxycycline + metronidazole or moxifloxacin.