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.
Why Amoxicillin–Clavulanate?
Single‑agent cover for Eikenella and anaerobes, plus Staph/Strep
Excellent oral bioavailability; standard first‑line for human‐bite wounds
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
Alternative for Penicillin Allergy
Doxycycline + metronidazole or moxifloxacin monotherapy are guideline‑endorsed alternatives in true β‑lactam allergy
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.
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