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SOURCE

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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.

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DEFINITION

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

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ETIOLOGY

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  • 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.

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PATHOPHYSIOLOGY

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  • 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.

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EPIDEMIOLOGY

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  • 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.

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CLINICAL PRESENTATION

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  • 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.

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SIGNS AND SYMPTOMS
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  • All bites:

    • Pain.

    • Swelling.

    • Clear or purulent discharge.

  • Animal bite:

    • Fever uncommon.

    • Concomitant adenopathy or lymphangitis is uncommon.

  • Human bite:

    • Lymphadenopathy.

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DIAGNOSIS

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MEANS OF CONFIRMATION AND DIAGNOSIS
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  • Patient report of attack and/or injury.

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LABORATORY TESTS
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  • 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.

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

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DESIRED OUTCOMES

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  • Resolution of infection and prevent further complications.

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TREATMENT: GENERAL APPROACH

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  • Animal bite: obtain immunization history ...

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