Infected Animal Bite

Aka: Infected Animal Bite, Infected Mammalian Bite, Dog Bite Infection, Infected Dog Bite, Infected Cat Bite, Antibiotic Prophylaxis Indications After Animal Bite

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II. Indications: Antibiotic Prophylaxis Indications

  1. See Bite Wound Antibiotic Prophylaxis
  2. Most dog and Human Bites, and all Cat Bites are treated with Antibiotics if the skin has been broken
  3. Moderate to severe bites wounds with crush injury
  4. Puncture Wounds (esp. deep wounds that may have punctured bone, tendon or joint)
  5. Deep wounds (esp. surgically closed)
  6. Hand, foot or genital bite wounds
  7. Immunocompromised patient (including Asplenia)

III. Causes: Bacterial Infection

  1. See Animal Bite
  2. See Human Bite
  3. Pasteurella Multocida (20-50% of all dog and Cat Bite infections)
    1. Typically Cat Bites, but can occur in Dog Bites as well
    2. Infection rapid onset (<24 hours) and progression is typical of P. multocida
  4. Pasteurella canis
    1. Resistant to Dicloxacillin, Cephalexin, Clindamycin and Erythromycin
  5. Streptococcus
  6. Staphylococcus Aureus
  7. Escherichia coli
  8. Moraxella
  9. Corynebacterium
  10. Neisseria
  11. Anaerobic Bacteria
    1. Bacteroides
    2. Fusobacterium
    3. Peptostreptococcus
  12. Capnocytophaga canimorsus (DF-2)
    1. Emerging Infection in dog and Cat Bites with risk of secondary Sepsis, Meningitis, endocarditis, DIC, Acute Renal Failure
    2. Increased risk in Asplenic patients or with Alcohol Abuse (or other Immunocompromised state)
    3. Gram Negative Bacteria responds to Augmentin

IV. Risk Factors: Infection

  1. Wound Location
    1. Face
    2. Foot or Hand Wound
    3. Genitalia
    4. Overlying a prosthetic joint
    5. Penetration of underlying structures (e.g. joint, bone, tendon)
  2. Wound Type
    1. Crush Injury
    2. Puncture Wound
    3. Delayed presentation (>8 to 12 hours)
    4. Heavily contaminated wound or foreign body
  3. Underlying Disease
    1. Chronic Disease
    2. Chronic extremity edema
    3. Vascular Insufficiency (e.g. Peripheral Arterial Disease, Venous Insufficiency, Lymphedema)
    4. Diabetes Mellitus
    5. Immunosuppression
    6. Liver disease
    7. Prior Mastectomy
    8. Prosthetic Valve
    9. Prosthetic Joint
    10. Asplenia (post-splenectomy)
    11. Systemic Lupus Erythematosus (SLE)

V. Management: Outpatient Antibiotics

  1. Close interval follow-up in first 24 to 48 hours
  2. Other concerns
    1. See Animal Bite
    2. Tetanus Prophylaxis
    3. Rabies Postexposure Prophylaxis
    4. Perform wound cleaning, copious Wound Irrigation, and foreign body and devitalized tissue Debridement
    5. Wound closure if indicated
  3. Antibiotic duration guidelines
    1. Prophylaxis after Dog Bite: 3 to 5 days (up to 7 days in some guidelines)
    2. Cellulitis Present: 10 to 14 days
    3. Bone or Joint Infection: Typically 4 to 6 weeks
  4. First Line Antibiotics (adults and children)
    1. Amoxicillin-Clavulanate (Augmentin)
      1. Child: 45 mg/kg/day divided twice daily up to 875 mg twice daily
      2. Adult: 875 mg twice daily
  5. Alternative Antibiotics for Penicillin Allergic
    1. Adults
      1. Combination protocol: Clindamycin with Ciprofloxacin
        1. Clindamycin 300 mg every 8 hours AND
        2. Ciprofloxacin 500 mg twice daily (or other Fluoroquinolone)
      2. Combination protocol: Doxycycline AND Clindamycin (or Metronidazole)
        1. Doxycycline 100 mg orally twice daily (do not use in pregnancy) AND
        2. Clindamycin 300 mg every 8 hours (or Metronidazole)
      3. Combination protocol: Cefuroxime with Metronidazole
        1. Cefuroxime (Ceftin) 500 mg twice daily AND
        2. Metronidazole (Flagyl), 250 to 500 mg four times daily
      4. Combination protocol: Clindamycin with Trimethoprim-Sulfamethoxazole
        1. Clindamycin 300 mg every 8 hours AND
        2. Trimethoprim-Sulfamethoxazole (Bactrim, Septra) DS twice daily
      5. Combination protocol: Penicillin VK with Dicloxacillin
        1. Penicillin VK 500 mg 4 times daily AND
        2. Dicloxacillin 500 mg 4 times daily
    2. Pregnancy
      1. Clindamycin with Trimethoprim-Sulfamethoxazole (see protocol above) OR
      2. Alternatively, Azithromycin (Zithromax), 250 to 500 mg daily
      3. Monitor closely to high risk of treatment failure
    3. Children
      1. Combination protocol
        1. Clindamycin 10 to 25 mg per kg divided every 8 hours AND
        2. Trimethoprim-Sulfamethoxazole (Bactrim, Septra)
          1. Dose: 8 to 10 mg/kg/day (trimethoprim component) divided twice daily
  6. Alternative Antibiotics for questionable compliance
    1. Ceftriaxone (Rocephin) IM daily
  7. Additional Antibiotic coverage considerations
    1. MRSA Coverage
      1. Consider in severe wounds, esp. if prior MRSA Infection
    2. Tularemia coverage
      1. Consider in Cat Bite (esp. outdoor cats)
      2. Cats acquire Tularemia by ingesting infected rodents

VI. Management: Inpatient Antibiotics

  1. Indications
    1. Systemic signs of infection (fever, chills...)
    2. Lymphangitis or Lymphadenitis
    3. Rapidly spreading Cellulitis
    4. Advancement of Cellulitis past one joint
    5. Tenosynovitis
    6. Septic Arthritis
    7. Osteomyelitis
    8. Nerve involvement
  2. First-Line Intravenous Antibiotics
    1. Unasyn (Ampicillin/Sulbactam) 3 g every 6 hours
  3. Second-Line Intravenous Antibiotics
    1. Piperacillin/Tazobactam 3.375 g every 6 hours
    2. Ceftriaxone 2 g every 24 hours AND Clindamycin 600-900 mg every 8 hours
    3. Trimethoprim/Sulfamethoxazole AND Clindamycin 600-900 mg every 8 hours
  4. Consultations to consider
    1. General Surgery
    2. Orthopedics
    3. Plastic surgery

VII. References

  1. Cowling and House (2017) Crit Dec Emerg Med 31(5): 15-20
  2. Gilbert (2017) Sanford Guide, accessed 5/9/2017
  3. Shivaprakash and Vezzetti (2022) Crit Dec Emerg Med 36(2): 3-10
  4. Ellis (2014) Am Fam Physician 90(4):239-43 [PubMed]
  5. Ortiz (2023) Am Fam Physician 108(5): 501-5 [PubMed]
  6. Presutti (2001) Am Fam Physician 63(8):1567-72 [PubMed]
  7. Presutti (1997) Postgrad Med 101:243 [PubMed]
  8. Talan (1999) N Engl J Med 340:85-92 [PubMed]

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