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Source: Fish DN, Pendland SL, Danziger LH. Skin and Soft-Tissue Infections. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th edition. Accessed July 22, 2012.

  • Soft-tissue injury from cat, dog, or human bite.

  • Animal bite
    • Dogs: Most infections polymicrobial; most frequently isolated organisms Pasteurella spp., streptococci, staphylococci, Moraxella, and Neisseria. Most common anaerobes Fusobacterium spp., Bacteroides spp., Porphyromonas, and Prevotella.
    • Cats: Infections frequently caused by P. multocida.
  • Human bite
    • Most often caused by normal oral flora, including both aerobic (Streptococcus spp., Staphylococcus spp., and Eikenella corrodens) and anaerobic (Fusobacterium, Prevotella, Porphyromonas, and Peptostreptococcus spp.) microorganisms.

  • Animal bite
    • High risk of infection owing to pressure exerted during bite and large number of potential pathogens.
    • Cat bites: higher incidence of septic arthritis and osteomyelitis
    • Dog bites: crush injuries with much devitalized tissue
  • Human bite
    • More serious and prone to infection than animal bites.
    • Hand (most common): Force of punch to mouth causes breach in capsule of metacarpophalangeal joint, leading to direct inoculation of bacteria into joint or bone.
      • Tendons carry bacteria into deeper spaces of hand, resulting in more extensive infection.

  • Animal bites
    • Dog bites more common than cat bites
      • Most commonly seen in males <20 years of age
      • Locations:
        • 70% to extremities
        • Facial bites in children <5 years of age
    • Infection rates with cat bites more than double those seen with dog bites
  • Human bites
    • Most often involve hands, either self-inflicted or due to traumatic laceration (e.g., “fight bites”)

  • Animal bite
    • 20% of dog bites and 30–50% of cat bites become infected
    • Puncture wound
    • Have not sought medical attention within 12 hours of injury
    • Age >50 years
  • Human bite
    • Infections occur in 10–50% of bites.

  • Animal bite: Patient generally presents either immediately after bite for general wound care or >12 hours after injury due to clinical signs of infection.
  • Human bite: Most clenched-fist injuries are infected by time patients seek medical care and require hospitalization.

Signs and Symptoms

  • Animal bite:
    • Pain
    • Swelling
    • Purulent discharge
    • Localized cellulitis
    • Fever uncommon
    • Concomitant adenopathy or lymphangitis in <20% of cases
  • Human bite:
    • Pain
    • Swelling
    • Purulent discharge
    • Decreased range of motion
    • Adenopathy in adjacent lymph nodes

Means of Confirmation and Diagnosis

  • Patient report of attack and/or injury

Laboratory Tests

  • Animal bite:
    • Culture for aerobic and anaerobic bacteria; not needed if <8 hours or >24 hours elapsed since bite and no signs of infection
  • Human bite
    • Complete blood count (CBC): leukocytosis present with severe infection
    • Culture for aerobic and anaerobic bacteria


  • Human bite: radiographic evaluation if damage to bone or joint suspected.

  • Resolution of infection

  • Animal ...

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