2. Bite Wounds
• Serious infections can result from wounds
that are caused by bites from animals and
humans
• Organisms recovered from bite wounds
generally originate from the oral cavity of the
biting animal, as well as from the patient's
skin flora
3. Bite Wounds
• Anaerobes have been isolated from animal and human bite
wound infections, especially those associated with abscess
formation
• Common complications:
– lymphangitis, septic arthritis, tenosynovitis, and osteomyelitis
• Uncommon complications:
– endocarditis, meningitis, brain abscess, and sepsis
4. Bite Wound Overview
• >1 million animal bites occur in the United States each year
• Dog bites account for 80% to 90% of all bite wounds
• Incidence of dog bites is higher in young children than in
adults
• The bites in children frequently involving the head, face, or
neck
• 4% of patients seen in the ED for a dog-bite wound require
hospitalization
• 2% to 20% of dog-bite wounds become infected
• Each year, more than a dozen deaths are caused by dog
bites
5. Bite Wound Overview
• Cat bites account for 5% to 15% of bite wounds
• >½ occur in adults, and cat bites are more common
in women
• Cat bites are almost always puncture wounds, and
the rate of infection is estimated to be 30% to 80%
6. Bite Wound Overview
• Human bites account for 2% to 3% of all reported
bites with ¾ caused by aggressive acts
• Are either occlusional, usually seen in a sexual crime
or child abuse, or clenched fist, usually the result of
punching a person in the mouth
• An estimated 10% to 50% of human-bite wounds
become infected
7. Microbiology
(General)
• Streptococcus pyogenes has been found in human
bites
• Pasteurella multocida in animal bites (60% of
bacteremia cases) with Pasteurella septica causing
central nervous system symptoms
• Eikenella corrodens in both animal and human bites
(although predominantly in human bites)
8. Microbiology
• Dog bites: Capnocytophaga canimorsus (formerly
CDC group DF-2), Capnocytophaga cynodegmi,
Neisseria weaveri (formerly M-5), Weeksella
zoohelcum (formerly IIj), Neisseria canis,
Staphylococcus intermedius, NO-1, and EO-2.
• Pig bite: Flavobacterium IIb-like organisms
• Horse and sheep: Actinobacillus species
9. Microbiology
• Marine setting: Vibrio species, Plesiomonas
shigelloides, Aeromonas hydrophila, and
Pseudomonas species
• Serious infections: tularemia (cats), herpes B
virus (monkeys), rat-bite fever or sodoku (rats),
hepatitis B virus (humans), leptospirosis (dogs
and rodents), and rabies (dogs and other
mammals)
10. Microbiology
• Human Bites: Staphylococcus aureus,
Penicillin-resistant Gram-negative rods, alone
or in mixed cultures, have been reported in
24% to 43% of cultured human bite wounds,
anaerobic bacteria have been recovered from
human bites in adults and children (50%)
11. Microbiology
• Predominant isolates were anaerobic Gram-
negative bacilli: Prevotella, Porphyromonas
species, Bacteroides species, Fusobacterium
nucleatum, and anaerobic Gram-positive cocci
• Predominant aerobes: S aureus, group A beta-
hemolytic streptococci, and E corrodens
12. Microbiology
• Common isolates: Streptococcus anginosus
(52%), S aureus (30%), E corrodens (30%), F
nucleatum (32%), and Prevotella melaninogenica
(22%)
• Many Prevotella and S aureus strains were beta-
lactamase producers
13. Microbiology
• Candida species were found in 8% of wounds,
with Fusobacterium, Peptostreptococcus, and
Candida species isolated more frequently from
occlusional bites than from clenched-fist injuries
• Normal oral flora, rather than skin flora, to be
the source of most bacteria isolated from human
bite wound cultures
14. Signs/Symptoms
• Signs and symptoms that emerge following a bite
depend on the type of animal inflicting the injury
– immediate local or systemic symptoms can be severe following
bites by venomous animals (e.g., snakes, lizards, spiders)
– Human bites and dog bites can develop infection rapidly because of
direct inoculation of oral and skin flora into the wound
• Human bites are typically more serious than animal bites, particularly
clenched-fist injuries
– Eschariform lesions in persons appearing to be ill may suggest the
presence of C canimorsus infection
15. Signs/Symptoms
With a clenched-fist injury:
– Teeth can cause deep lacerations that implant oral and skin
organisms into the joint capsules or dorsal tendons, which may
cause septic arthritis or osteomyelitis
– Medical status of the source of the human bite (e.g., hepatitis, HIV,
other transmittable diseases
– Radiographs are recommended for this type injury
– sedimentation rate or C-reactive protein level can help
16. Signs/Symptoms
Dog Bites:
• 2% to 5% of all typical dog bite wounds become infected
• The dog's rabies status needs to be ascertained
• Gram's stain and culture for both aerobic and anaerobic bacteria
should be obtained from human and animal bite wounds
• Wounds contaminated by soil or vegetative debris should be
cultured for mycobacterium and fungi
17. Management
Good wound management includes:
• Evaluation
• Proper local care
• Antimicrobial agents
• An incident of an animal bite should be reported to the local health
authorities
18. Management
Evaluation:
• Patient's medical history (e.g., current medications, splenectomy,
mastectomy, allergies, chronic disease, immunosuppression)
• Type of attack (e.g., type of animal, provoked or unprovoked)
• Examining the wound and related structures (eg, odor, depth, type,
and location; range of motion; joint involvement; edema; nerve and
tendon damage; and presence of infection)
• Obtaining wound cultures and X-rays (when bone penetration is
suspected)
• Determining wound approximation
19. Management
Local Care:
Cleansing- soap or a quaternary ammonium compound and water
•
Exploration- for damage to tissue caused by crushing or tearing with X-ray
•
examination for fractures and foreign bodies should be done when feasible
Irrigation- 150mL or more of NSS or lactated Ringer's solution
•
Debridement- Devitalized tissue should be removed
•
Drainage- TLS or JP drain system
•
Suturing- Controversy still exists as to whether clinically uninfected bite wounds
•
that have been seen within 24 hours should be surgically closed but the
guideline is that puncture wound margins should be excised and left open after
irrigation, and margins of other wounds should be excised and primary closure
performed, with or without drainage
– Delayed primary closure or edge approximation should be done in wounds associated
with crush injuries, preexisting edema, and injuries to the hands and feet.
22. Management
• Monkeys may carry B virus, so wounds should be thoroughly cleansed and
irrigated for at least 15 minutes, and viral cultures should be performed after
cleansing. Serum for acute viral B virus-specific serology should be stored at -
20°C and compared with a second sample obtained 21 days later. Antiviral
therapy with acyclovir, valacyclovir, or famciclovir should be given to those
persons with moderate- or high-risk wounds
• Hand bites are at high-risk of deep damage and severe infection. For human
bites, the wounds should be opened, debrided, and thoroughly irrigated;
primary closure and tendon and nerve repair should be delayed. Dog bites can
be considered clean following debridement and irrigation, and primary closure
can be performed
• In severe cases, hospitalization may be necessary, with immobilization by
splinting or bulky dressings and elevation. Rabies prevention-including
hyperimmune serum and active immunization-should be given after dog bites as
indicated
23. Management
• Facial bites, especially those in children, require meticulous
management. Most patients do well with careful debridement, ample
irrigation and cleansing, and loose closure by suture. Close follow-up is
required for at least 5 days. Because subsequent plastic reconstruction
may be needed, it may be useful to consult with a plastic surgeon at
the time of initial repair.
• Early management of all human bites, especially those to the hand,
must be thorough and vigorous. Clenched-fist injuries require more
intensive care, preferably by a hand surgeon, to evaluate the
seriousness of injury to tendon, sheath, joint, joint capsule, and bone.
24. Management
Antimicrobials:
• Tetanus toxoid booster if adequately immunized in the past, with the
last dosage received within the past 10 years. Tetanus immune
globulin (human) is required if tetanus immunization has not taken
place or is inadequate
• Antimicrobial treatment should be administered for all bite wounds,
with the exception of those patients who present 72 hours or more
after injury with no clinical signs of infection. Antimicrobial therapy for
bite wounds is not usually prophylactic, but rather a therapeutic
intervention
• Antibiotics chosen for prophylaxis or treatment should be based on
bacteriology. It is advisable to treat all patients having deep bite
wounds with antibiotics, including puncture wounds, facial bites, and
any wound over tendon or bone
25. Management
• Obtaining cultures is helpful in guiding the therapy
• Penicillin or ampicillin are the most active agents against P
multocida and the other oral flora; however, S aureus and about
50% of the anaerobic Gram-negative bacilli recovered in human
bite wounds are resistant to this drug
• Isolation of beta-lactamase-producing organisms from more
than 40% of bite wounds excludes the use of penicillin for bite
infections
26.
27.
28. Management
• Although oxacillin is effective against S aureus, it has poor
activity against many bite isolates
• Doxycycline is a good alternative; however, it should not be
used in young children
• If S aureus is suspected (based on the Gram's stain of aspirate,
which is specific but not sensitive), penicillin (to cover
streptococci) and penicillinase-resistant penicillin should be used
• Augmentin has been shown to be effective in treating human
bites and dog bites and baring allergy is often 1st line
29. Management
• Clindamycin and penicillinase-resistant penicillin should not be
administered without penicillin because of poorer activity against P
multocida
Erythromycin is generally ineffective against Fusobacterium, P
•
multocida, Moraxella species, and peptostreptococci
• Azithromycin is generally more active than clarithromycin against all
Pasteurella species
– Azithromycin and clarithromycin are only modestly effective against E
corrodens and Peptostreptococcus species.
• Cefoxitin or penicillin with a first-generation cephalosporin plus a beta-
lactamase-resistant penicillin or Unasyn will provide adequate
parenteral therapy for animal or human bites
• The newer quinolones (eg, gatifloxacin, moxifloxacin) are active
against all major bite wound pathogens, including anaerobic bacteria;
however, these agents are not approved for use in children
30. Management
• E corrodens, a capnophilic Gram-negative rod that is part of
normal oral flora, can be recovered from 25% of human bite
wounds
• Susceptible to penicillin, ampicillin, and quinolones, E corrodens
is resistant to clindamycin, methicillin, nafcillin, and oxacillin;
certain strains are also resistant to cephalosporins
• Any isolated E corrodens, therefore, should have susceptibility
testing if cephalosporin therapy is considered.
• Most bite wounds can be sutured with good results and an
acceptable infection rate, with a 7- to 14-day course of abx for
infections limited to soft tissue; a minimum of 21 days of
therapy is generally required for infection involving joints or
bones
31. Complications
• Local wound infection with lymphangitis, local abscess, septic
arthritis, tenosynovitis, and osteomyelitis
• Less common complications include endocarditis, meningitis,
brain abscess, and sepsis with DIC (disseminated intravascular
coagulation)
• Individuals prone to complications include those receiving
systemic corticosteroids and those suffering from lupus
erythematosus and acute leukemia
• Hand wounds have a high rate of infection (30% or more) and
complications are common with disastrous functional
consequences
• Rabies must also be considered with dog bite wounds
