DESCRIPTION

• 3rd most common bite (after dogs and cats)
• Most bites (up to 75%) occur during aggressive acts.
• 15–20% are related to sexual activity (love nips).
• 2 types of bites:
  • Occlusional bites: Laceration or crush injury to affected body part:
    • Occurs when human teeth bite into the skin
    • More prone to infection than animal bites
  • Clenched-fist injuries (CFIs) (CFIs; most serious type): Present as small wounds over metacarpophalangeal joints in dominant hand (fight bites):
    • Sustained from a clenched fist striking the mouth and teeth of another person
• With joint relaxation from the clenched position:
  • Puncture site sealed
  • Oral bacteria inoculated in the anaerobic setting within the joint
  • Bacterial inoculation carried by the tendons deeper into the potential spaces of the hand
  • Increases chances for a more extensive infection

ETIOLOGY

• Aerobic and anaerobic organisms:
  • Most common:
    • Streptococcus
    • Staphylococcus
  • Others:
    • Eikenella corrodens
    • Haemophilus influenzae
    • Peptostreptococcus
    • Corynebacterium
    • E. corrodens exhibits synergism with Streptococcus, Staphylococcus aureus, Bacteroides, and gram-negative organisms
• Although rare, case reports of viral transmission via bites (hepatitis, HIV, and herpes)

[Outline]

• DESCRIPTION
• ETIOLOGY

SIGNS AND SYMPTOMS

• Location:
  • Upper extremities (60–75%)
  • Head and neck (15–20%)
  • Trunk (10–20%)
  • Lower extremities (~5%)
• Frequent complications:
  • Cellulitis
  • Serious deep-space infections (septic arthritis and osteomyelitis)
  • Fractures and tendon injuries
  • Hand bites have highest rates of infection.

History

• Time of injury
• Patient allergies
• Relevant medical history (immune status)
• Last tetanus shot
• HIV, hepatitis B status of person inflicting bite

Physical Exam

• Record the location and extent of all injuries.
• Document any swelling, crush injuries, or devitalized tissue.
• Note the range of motion of affected areas.
• Note the status of tendon and nerve function.
• Document any signs of infection, including regional adenopathy.
• Document any joint or bone involvement.

ESSENTIAL WORKUP

Careful physical exam for involvement of deep structures and foreign bodies:

• Examine the deepest part of clenched-fist bites while putting the fingers through full range of motion to check for extensor tendon lacerations and joint violation.

DIAGNOSIS TESTS & INTERPRETATION

Lab

• Aerobic and anaerobic cultures from any infected bite wound
• Cultures not indicated if wounds not clinically infected
• CBC if signs of significant infection.
• Electrolytes, glucose, BUN, and creatinine:
  • For diabetic patients or those with significant infections

Imaging

• Generally not helpful
• Plain radiograph indications:
  • Fracture
  • Suspect foreign body (e.g., tooth)
  • Baseline film if a bone or joint space has been violated in evaluating for osteomyelitis
  • For infection in proximity to a bone or joint space
• Ultrasound can be useful in differentiating abscess from cellulitis

DIFFERENTIAL DIAGNOSIS

Bite injuries from animals:

• Sharper teeth cause more punctures and lacerations than human teeth, which usually cause more crush-type injuries.

Other Considerations

• In suspected sexual abuse:
  • Check for a central area of bruising or "hickey" from suction
• Linear abrasions or bruises on both the dorsal and palmar/plantar surfaces of the hand or foot:
  • Highly suggestive of bite marks
  • Lesions on one extremity should prompt a search for lesions on the other extremities.
• An intercanine distance of > 3 cm indicates permanent dentition (present only if the attacker is > 8 yr)
• If abuse suspected:
  • Rub a saline-moistened swab in the wound to collect any saliva and then place in a paper envelope for analysis.
  • Obtain photographs.
  • Notify authorities.

[Outline]

• SIGNS AND SYMPTOMS
• ESSENTIAL WORKUP
• DIAGNOSIS TESTS & INTERPRETATION
• DIFFERENTIAL DIAGNOSIS

PRE-HOSPITAL

Control bleeding with direct pressure.

INITIAL STABILIZATION/THERAPY

ABCs: Ensure patent airway and adequate peripheral tissue perfusion

ED TREATMENT/PROCEDURES

• Wound irrigation:
  • Copious volumes of normal saline irrigation with an 18G needle or plastic catheter tip aimed in the direction of the puncture
  • Care should be taken not to inject fluid into the tissues.
• Débridement:
  • Remove any foreign material, necrotic skin tags, or devitalized tissues.
  • Do not débride puncture wounds.
  • Remove any eschar present so that underlying pus may be expressed and irrigated.
• Clenched-fist injuries:
  • Immobilize
  • Splint in a position of function that maintains the maximal length of ligaments and intrinsic muscles.
  • Use a bulky hand dressing
  • Consultation with hand surgeon regarding operative irrigation/exploration of wound
  • Elevation for several days until any edema resolved
  • Sling for outpatients
  • Place the hand in a tubular stockinette attached to an IV pole for inpatients.
  • Administer antibiotics
• Do not perform primary repair of avulsion wounds.
• Wound closure:
  • Closing wounds increases risk of infection and must be balanced with scar formation and effect of leaving wound open to heal secondarily.
  • Do not suture infected wounds or wounds > 24 hr after injury.
  • Repair of wounds > 8 hr after bite: Controversial.
  • Close facial wounds up to 24 hr after bite (warn patient of high risk of infection).
  • Infected wounds and those presenting > 24 hr should be left open.
  • May approximate the wound edges with Steri-Strips and perform a delayed primary closure.
  • Do not suture CFIs.
• Prophylactic antibiotics controversial for low-risk bites
• Antibiotics for outpatients with:
  • Moderate to severe injuries with crush injury or edema
  • Involvement of the bone or a joint
  • Hand bites
  • Wounds near a prosthetic joint
  • Underlying disease (diabetes, prior splenectomy, or immunosuppression) that increases the risk of developing a more serious infection
• Tetanus prophylaxis
• Refer for possible testing/surveillance for HIV infection.

MEDICATION

First Line

• Amoxicillin/clavulanic acid (Augmentin): 500/125 mg (peds: 40 mg/kg/24h) q8h PO
• Ampicillin–sulbactam (Unasyn): 3 g q6h IV
• Piperacillin–Tazobactam (Zosyn): 4.5 g q8h IV
• Ticarcillin–clavulanate (Timentin): 3.1 g q4h IV
• Ceftriaxone (Rocephin): 1 g/d plus Metronidazole (Flagyl): 500 mg q8h

Second Line

• 2 drug therapy: 1 of the following below + anaerobic coverage:
  • Trimethoprim–sulfamethoxazole (Septra DS): 1 tablet q12h (peds: 8 mg/kg trimethoprim and 40 mg/kg sulfamethoxazole per day divided into 2 daily doses) PO
  • Penicillin (Penicillin VK): 500 mg (peds: 50 mg/kg/24h) PO q6h
  • Ciprofloxacin (Cipro): 500–750 mg q12h PO or 400 mg q12h IV
  • Doxycycline: 100 mg PO BID
• + (anaerobic coverage):
  • Clindamycin (Cleocin): 150–450 mg (peds: 8–20 mg/kg/24h) PO q6h or 600–900 mg (peds: 20–40 mg/kg/24h) IV q8h
  • Metronidazole (Flagyl): 500 mg PO TID (peds: 10 mg/kg/dose TID)

[Outline]

• PRE-HOSPITAL
• INITIAL STABILIZATION/THERAPY
• ED TREATMENT/PROCEDURES
• MEDICATION

DISPOSITION

Admission Criteria

• Infected wounds at presentation
• Severe/advancing cellulitis/lymphangitis
• Signs of systemic infection
• Infected wounds that have failed to respond to outpatient (PO) antibiotics

Discharge Criteria

• Healthy patient with localized wound infection:
  • Discharge on antibiotics with 24-hr follow-up.
• Noninfected wounds
  • 48-hr follow-up

Geriatric Considerations

• Human bite marks rarely occur accidentally; good indicators of inflicted injury.
• Consider elder abuse.

Pediatric Considerations

• Human bite marks rarely occur accidentally; good indicators of inflicted injury.
• If intercanine distance > 3 cm, bite likely from an adult. Consider child abuse.

Issues for Referral

Suspected child abuse

FOLLOW-UP RECOMMENDATIONS

• Hand specialist referral/follow-up for infected hand wounds
• Healthy patient with localized wound infection: Discharge on antibiotics with 24-hr follow-up.
• 48-hr follow-up for noninfected wounds

[Outline]

• DISPOSITION
• FOLLOW-UP RECOMMENDATIONS

• Examine the deepest part of clenched-fist bites while putting the fingers through full range of motion to check for extensor tendon lacerations and joint violation.
• Obtain hand consultation for operative irrigation for all patients with clenched-fist lacerations due to the high rate of infection.
• An intercanine distance of > 3 cm indicates permanent dentition (present only if the attacker is > 8 yr).

ICD9

• 879.8 Open wound(s) (multiple) of unspecified site(s), without mention of complication
• 882.0 Open wound of hand except finger(s) alone, without mention of complication
• 882.1 Open wound of hand except finger(s) alone, complicated

ICD10

• S11.90XA Unsp open wound of unspecified part of neck, init encntr
• S21.90XA Unsp open wound of unspecified part of thorax, init encntr
• S61.409A Unspecified open wound of unspecified hand, init encntr

[Outline]

• ICD9
• ICD10

• Broder J, Jerrard D, Olshaker J, et al. Low risk of infection in selected human bites treated without antibiotics. Amer J Emerg Med. 2004;22(1):10–13.
• Brook I. Microbiology and management of human and animal bite wound infections. Prim Care. 2003;30(1):25–39.
• Endom E. Initial management of animal and Human Bites. UpToDate, Oct 25, 2012.
• Medeiros I, Saconato H. Antibiotic prophylaxis for mammalian bites. Cochrane Database Syst Rev. 2001;(2):CD001738.
• Pickering L. Red book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003.
• Smith PF, Meadowcroft AM, May DB. Treating mammalian bite wounds. J Clin Pharm Ther. 2000;25:85–99.

See Also (Topic, Algorithm, Electronic Media Element)

Bite, Mammal

Daniel T. Wu