Bite Wounds

SOURCE

Source: Fish DN. Skin and soft-tissue infections. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146071658. Accessed March 23, 2017.

DEFINITION

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

ETIOLOGY

• 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 Pasteurella 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.

PATHOPHYSIOLOGY

• 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.

EPIDEMIOLOGY

• Animal bites.

  • Dog bites more common than cat bites.

    • 60% of all animal bite wounds requiring medical attention.

    • Most commonly seen in children aged 5–9 years of age.

    • Locations:

      • Extremities.

      • Facial and neck bites in children <5 years of age.

  • Infection rates with cat bites more than double those seen with dog bites.

    • Mostly reported in women and the elderly.

    • Locations:

      • Upper extremities and face.

      • Facial and neck bites in children <5 years of age.

CLINICAL PRESENTATION

• 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

• All bites:

  • Pain.

  • Swelling.

  • Clear or purulent discharge.

• Animal bite:

  • Fever uncommon.

  • Concomitant adenopathy or lymphangitis is uncommon.

• Human bite:

  • Lymphadenopathy.

DIAGNOSIS

MEANS OF CONFIRMATION AND DIAGNOSIS

• Patient report of attack and/or injury.

LABORATORY TESTS

• Culture for aerobic and anaerobic bacteria; not needed if <8 hours or >24 hours elapsed since bite and no signs of infection.

• White blood counts should be monitored for resolution of infection if initially elevated.

IMAGING

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

DESIRED OUTCOMES