What is the most likely organism to infect animal bite wounds?
- rapid evolution of an intense
- with substantial pain and swelling
- in 70% within 24 hours of the initial injury in 70% of cases
- in 90% by 48 hours
- Infections usually exhibit
and purulent discharge.
- has resulted in abscess formation, septic arthritis, osteomyelitis,
sepsis, meningitis, endocarditis, and pneumonia.
- Fever, regional adenopathy, and lymphangitis are seen in fewer than 20% of
- Wounds in proximity to bones or joints may be associated with the
complications of septic arthritis, osteomyelitis, and tenosynovitis.
- If there is edema of the extremity, the risks of sepsis and serious
cellulitis are increased.
- facultatively anaerobic, bipolar staining, gram-negative coccobacillus
- is a primary pathogen in animals.
- found in the oral flora of 70% to 90% of cats, 25% to 50% of dogs, and the
mouths of many other animals.
- Transmission occurs from the bite
or scratch of a cat, dog, or less commonly, other animal.
- Cats cause only 5% of bites presenting to emergency departments, but these
bites are associated with a high risk of infection (80%)*
- Dogs cause the majority (90%) of bites presenting to emergency
departments but are associated with a low risk of infection (5%)*
- vs Chief Pearl: The rate of infection after a
dog bite is about 15-20% (just like human bites), and cat bites have an
infective rate of >/= 50%
- Respiratory spread from animals to
humans also occurs.
- Human-to-human spread has not been documented.
- the incubation period usually is
less than 24 hours.
- can be isolated from skin lesion drainage or other sites of infection.
- laboratory differentiation is
not difficult, although ~ resembles several other organisms morphologically (eg,
Haemophilus influenzae, Neisseria sp, and fastidious gram-negative rods,
particularly Actinobacillus) and grows on many culture media at 98°F (37°C).
When to suture? When to Xray? When to refer?
- In general,
recent, apparently noninfected, low-risk lesions may be sutured after thorough
wound cleansing, irrigation, and debridement (although
some prefer to approximate the wound edges with adhesive strips or
- Hand and foot bites
- have a greater chance of becoming infected and should have surgical
evaluation. When to refer to a hand surgeon: if suspicion of underlying
tendon or bony compromise.
- Radiographs are indicated for a
patients whose hands have been bitten by an animal. X-rays may
reveal occult fx or foreign bodies.
- All hand wounds should be left
open (increased risk of infection).
- Face bite wounds
- rarely become infected
- because of the cosmetic implications, should be closed whenever possible.
- Radiographs are indicated
for children who have been bitten on the scalp or face. X-rays may
reveal occult fx or foreign bodies
- Puncture wounds should be
left open (increased risk of infection)
- Human bites: see below
- Everybody bitten by an animal are at risk for tetanus. If no boosters in
last 5 years, give 0.5 mL Td. If doesn't have primary immunization complete,
give tetanus Ig (250 U IM)
Tetanus and Wound Care
- The drug of choice: amoxicillin-clavulanate.
Give one dose of unasyn IV and 3-5 days of augmentin1. Treat the
following (Red Book)
- Moderate or severe bite wounds, especially if
edema or crush injury is present
- Puncture wounds, especially if penetrating
bones, tendon sheath, or joint has occurred
- Facial bites
- Hand and foot bites
- Genital area bites
- Wounds in immunocompromised and asplenic
- For penicillin-allergic adults: cefuroxime 500 bid or (clinda 300 q4h +
cipro 500 bid)1
- For penicillin-alergic children: cefurox 30/kg div bid or (clinda +
- Other effective agents include penicillin, ampicillin, cefuroxime, cefpodoxime, trimethoprim-sulfamethoxazole, and tetracycline.
- The duration of therapy usually is
7 to 10 days for local infections and 10 to14 days for more severe infections.
- Wound drainage or debridement may be necessary.
Followup should be in 24-48h to eval for infxn
Antibiotic treatment in special cases
- Many human bites are clenched fist injuries, which are particularly high
infection risks. Amoxicillin/clavulanate is recommended as above. Consider
passive immunization for hepatitis B with immune globulin. In high-risk
exposures (eg, known HIV-positive
patient, hollow bloody needle from high-risk patient), the recommended 3-drug
regimen (ie, zidovudine [ZDV] plus lamivudine [3TC] plus indinavir [IDV])
should begin within 60 minutes of exposure. Other retroviral agents can be
substituted for these agents. However, nevirapine is not recommended because
of several reported cases of life-threatening hepatotoxicity occurring during
patients who have been bitten by a dog with prophylactic penicillin due
to increased risk of sepsis and death due to the rare bacterial species
- For patients allergic to beta-lactam agents, tetracycline is effective,
but it should not be administered to children younger than 8 years of age.
infection, which frequently involves Staphylococcus
aureus, oral amoxicillin-clavulanate
or intravenous ampicillin-sulbactam or ticarcillin-clavulanate (for severe
infection) can be given.
- Parenterally administered broad-spectrum cephalosporins, such as
cefotaxime or cefoxitin, are active against P multocida in vitro, but the
therapeutic experience with these drugs for these infections is limited.
Other organisms. The incubation period for infections caused by these
pathogens is longer than P multocida; symptoms most likely would not be apparent
within 24 hours of an animal bite.
- Anaerobes. Eikenella corrodens is an anaerobic organism found in the oral flora of
humans. It frequently causes infections in human bite wounds, but it is not
usually a pathogen in animal bites.
- Francisella tularensis most commonly is acquired from a tick bite or from
contact with infected animal carcasses.
- Both S aureus and Streptococcus pyogenes are frequent causes of skin
infection and may complicate animal bites.
American Academy of Pediatrics. Pasteurella multocida infections. In:
Pickering LK, ed. 2000 Red Book: Report of the Committee on Infectious
Diseases. 25th ed. Elk Grove Village, Ill American Academy of
American Academy of Pediatrics. Bite wounds. In: Pickering LK, ed.
2000 Red Book: Report of the Committee on Infectious Diseases. 25th
ed. Elk Grove Village, Ill: American Academy of Pediatrics;
Garcia VF. Animal bites and Pasteurella infections. Pediatr Rev.
Ginsberg CM. Animal and human bites. In: Behrman RE, Kliegman RM,
Jenson HB, eds. Nelson Textbook of Pediatrics. 16th ed. Philadelphia,
Pa: WB Saunders Co; 2000:790-793
1. Consultant for Pediatricians May 2006