Chapter 15: Infectious Diseases

SYNDROMES AND COMPLEXES: BITE-WOUND INFECTIONS

Infections usually localized to the site of a bite. Rare sequelae include meningitis, brain abscess, endocarditis, and septic arthritis.

Epidemiology

• Infection in 10–15% of dog bites and approximately 50% of cat bites

• Greatest rate of infection after bites to the hands (28–63%)

  • ✓ Other common sites: Face/head/neck (6–16%), arm/leg (10–32%), and trunk (2–10%)

Etiology

• Usually polymicrobial; derived from oral flora of biting animal

• Cat and dog bite infections: Pasteurella canis (dog), Pasteurella multocida (cat), Capnocytophaga spp (dog) streptococci, Staphylococcus aureus, Moraxella spp., Neisseria spp., and anaerobes

• Human bites: S. aureus, viridans group Streptococci, Streptococcus pyogenes, Eikenella corrodens, Streptococcus intermedius, Neisseria spp., Haemophilus spp.

• Horse/sheep bite: Actinobacillus spp, Streptococcus equisimilis

• Marine settings/fish bite: Halomonas venusta, Vibrio spp, Aeromonas hydrophila, Plesiomonas shigelloides, Pseudomonas spp., Mycobacterium marinum

• Monkey bite: B virus

Pathophysiology

• Infection follows direct inoculation of bacteria into tissues.

• Hematogenous dissemination may occur.

Clinical Manifestations

• Note wound type (puncture, laceration, avulsion), edema, erythema, tenderness, drainage, depth of penetration, bruising, deformity, involvement of underlying structure, sensation, regional lymphadenopathy.

• Look for signs of systemic infection (e.g., fever, hypotension).

• Animal: Record type of animal, health of animal, provoked or unprovoked attack; observe for signs of rabies if applicable.

• Patient: History of asplenia (increased risk of Capnocytophaga spp.); immunosuppression or other illnesses; last tetanus immunization

Diagnostics

• Gram stain and culture of wound if time from injury is longer than 8 hours or if signs and symptoms of infection exist.

• Consider blood culture if fever present.

• Radiography indicated for penetrating injuries overlying bones or joints, suspected foreign body, or fracture.

Management

Immediate Management

• Examine for foreign body, irrigate with copious amounts of normal saline, and debride devitalized tissue.

• Suturing is controversial. Leave wound open if greater than 8 hours old or a puncture wound; primary wound closure for injuries to face and when cosmetic outcome is important

• Indications for operative exploration and debridement: Extensive tissue damage; involvement of metacarpophalangeal joint from clenched fist injury; cranial bites by large animals

Tetanus Prophylaxis

• Clean minor wounds: Administer tetanus toxoid if >10 years since last tetanus-containing vaccine dose, if vaccine history is unknown, or if fewer than three doses received.

• Puncture or severe wounds: If fewer than three doses received, administer tetanus toxoid and tetanus immunoglobulin. If patient has completed primary immunization but it has been ≥5 years since last tetanus-containing vaccine dose, administer tetanus toxoid.

Rabies Postexposure Prophylaxis

• Prophylaxis:

  • ✓ Active: Four doses of rabies vaccine on days 0, 3, 7, and 14 (five doses for immunocompromised hosts)

  • ✓ ...