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Bites - human and animal - Management
Which antibiotic should I use for someone with an animal bite?

  • For prophylaxis and treatment of an infected animal bite prescribe a 7–day course of co-amoxiclav.
  • For people who are allergic to penicillin prescribe:
    • Metronidazole plus doxycycline, or
    • Metronidazole plus oxytetracycline.
  • For children under 12 years old who are allergic to penicillin seek advice from a microbiologist.
  • Do not use erythromycin alone for prophylaxis or treatment of bite wounds.
  • For animal not covered in this guidance (e.g. pigs) seek specialist advice for the most appropriate antibiotic.
Basis for recommendation
  • These recommendations are based on published expert opinion from the Health Protection Agency [HPA, 2006a].
  • Co-amoxiclav is recommended as it is a broad-spectrum antibiotic and effective against most bacteria isolated from domestic animal bites.
  • Doxycycline/oxytetracycline plus metronidazole are recommended as:
    • Doxycycline and oxytetracycline have good activity against Pasteurella species (the most common pathogen), staphylococci, and streptococci [Smith et al, 2000; Talan et al, 2003].
    • Metronidazole is active against beta-lactamase-producing anaerobes.
  • Most infections that develop from dog and cat bites are caused by several organisms, with a mean of 2.8 to 3.6 bacterial species per wound culture, including an average of one anaerobic species per wound [Griego et al, 1995].
  • One study of infected cat and dog bites found that the most commonly isolated bacteria was Pasteurella (57% of dog bites and 75% of cat bites). Other common aerobes included streptococci, staphylococci, moraxella, and neisseria. Common anaerobes included fusobacterium, bacteroides, porphyromonas, and prevotella [Talan et al, 1999].
    • Pasteurella multocida is a Gram-negative pathogen that causes a rapid intense inflammatory response [Morgan, 2005; HPA, 2006b; Morgan and Palmer, 2007]:
      • It is found in dogs, cats, rabbits, chickens, turkeys, cattle, swine, and rodents.
      • It is is the most likely pathogen in an infected bite by a dog or cat presenting within 12 hours of the bite.
      • Complications include abscesses, cellulitis, and joint infections.
      • If septicaemia develops, the mortality may be as high a 30%.
      • Rarely it may cause pneumonic or lung abscesses in people with underlying pulmonary disease.
      • It is resistant to erythromycin and flucloxacillin.
      • It may cause tenosynovitis in hand bites and may lead to irreparable damage and amputation.
  • Co-amoxiclav is recommended because it is effective against most bacteria isolated from domestic animal bites. Penicillin will not cover all Staphylococcus aureus infections, or infections caused by anaerobes.
  • Metronidazole (in addition to tetracyclines) covers beta-lactamase-producing anaerobes.
  • Erythromycin should never be used alone in treating bite wounds — more than 80% of P. multocida are resistant, and serious clinical failures including meningitis have been documented following erythromycin treatment.

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