Bite Wounds

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. http://accesspharmacy.com/content.aspx?aid=8002378. 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

Imaging

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

• Resolution of infection

• Animal bite: obtain immunization history ...