Human & Animal Bites

Causative organisms

Human bites (including clenched-fist injuries) — Staphylococcus aureus, Eikenella corrodens, Streptococcus species, and beta-lactamase-producing anaerobes.

Animal bites — Pasteurella species, S. aureus, Capnocytophaga canimorsus, Streptococcus species, and anaerobes. Cat bites carry a higher risk of deep infection than dog bites.

Management

• Thorough cleaning, irrigation, debridement, elevation and immobilisation.
• Assess for deeper injury, devitalised tissue and retained foreign bodies — particularly important for bites from animals with small teeth.
• Post-exposure rabies/lyssavirus prophylaxis is required for some bites (e.g. bat bites).
• For human bites with blood exposure, consider blood-borne virus PEP (hepatitis B, HIV).
• Ensure tetanus immunisation is up to date — see the prophylaxis table in Wound Assessment & Laceration Repair.
• Swab the wound before starting antibiotics if it’s already infected.

Antibiotics for an infected wound

Line	Regimen
First	Oral amoxicillin-clavulanate
Penicillin hypersensitivity/MRSA	Oral metronidazole + oral doxycycline or trimethoprim-sulfamethoxazole
MRSA	Oral ciprofloxacin + oral clindamycin
Delayed access to oral antibiotics	IM procaine benzylpenicillin
Deeper tissue/systemic features	IV amoxicillin-clavulanate or piperacillin-tazobactam + vancomycin (if MRSA)
Deeper tissue, hypersensitivity	Oral/IV ciprofloxacin + clindamycin
Deeper tissue, hypersensitivity + MRSA	IV ciprofloxacin + vancomycin + metronidazole

When to give presumptive (prophylactic) antibiotics

For a non-infected wound, antibiotics are usually unnecessary in otherwise healthy patients with low infection risk (small wounds not involving deeper tissue, presenting within 8 hours, that can be adequately debrided/irrigated).

Give presumptive antibiotics if the risk of infection is high:

• Presentation delayed ≥8 hours
• A puncture wound that can’t be adequately debrided
• Wound on the hands, feet or face
• Involves deeper tissue (bone, joint, tendon) or an open fracture
• Patient is immunocompromised (e.g. asplenia, immunosuppressive medication), or has alcoholic liver disease or diabetes
• Cat bite

Referral

Consider surgical consultation for wounds on the hands, feet or face, or if infection progresses despite antibiotics. Surgical advice may also guide primary vs delayed wound closure.

From eTG.