Bite, Human

[Section Outline]

Description
Etiology

Author:

Daniel T.Wu

Description

Third 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—exhibits synergism with Streptococcus, Staphylococcus aureus, Bacteroides, and gram-negative organisms
  - Haemophilus influenzae
  - Peptostreptococcus
  - Corynebacterium
Although rare, case reports of viral transmission via bites (hepatitis, HIV, and herpes)

Diagnosis ⬆ ⬇

[Section Outline]

Signs and Symptoms
Essential Workup
Diagnostic Tests & Interpretation
Differential Diagnosis

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

Diagnostic Tests & Interpretation

Lab

Aerobic and anaerobic cultures from any infected bite wound
Cultures not indicated if wounds not clinically infected
CBC, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) if suspect 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

Treatment ⬆ ⬇

[Section Outline]

Prehospital
Initial Stabilization/Therapy
ED Treatment/Procedures
Medication

Prehospital

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
Debridement:
- Remove any foreign material, necrotic skin tags, or devitalized tissues
- Do not debride puncture wounds
- Remove any eschar present so that underlying pus may be expressed and irrigated
CFIs:
- 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): 875/125 mg PO b.i.d (peds: 20 mg/kg b.i.d)
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/24 hr) PO q6h
- Ciprofloxacin (Cipro): 500-750 mg q12h PO or 400 mg q12h IV
- Doxycycline: 100 mg PO b.i.d
+ (anaerobic coverage):
- Clindamycin (Cleocin): 150-450 mg (peds: 8-20 mg/kg/24 hr) PO q6h or 600-900 mg (peds: 20-40 mg/kg/24 hr) IV q8h
- Metronidazole (Flagyl): 500 mg PO t.i.d (peds: 10 mg/kg/dose t.i.d)

Follow-Up ⬆ ⬇

[Section Outline]

Disposition
Follow-up Recommendations

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

Pearls and Pitfalls ⬆ ⬇

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)

Additional Reading ⬆ ⬇

BroderJ, JerrardD, OlshakerJ, et al. Low risk of infection in selected human bites treated without antibiotics . Amer J Emerg Med. 2004;22(1):10-13.
BrookI. Microbiology and management of human and animal bite wound infections . Prim Care. 2003;30(1):25-39.
HarperM. Clinical manifestations and initial management of animal and human bites . UpToDate, 2017.
Red Book: 2015 Report of the Committee on Infectious Diseases. 30th ed.Elk Grove Village, IL: American Academy of Pediatrics; 2015.

See Also (Topic, Algorithm, Electronic Media Element)

Bite, Animal

Codes ⬆

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
874.8 Open wound of other and unspecified parts of neck, without mention of complication
879.6 Open wound of other and unspecified parts of trunk, without mention of complication
882.2 Open wound of hand except finger(s) alone, with tendon involvement
882 Open wound of hand except finger(s) alone
894.0 Multiple and unspecified open wound of lower limb, without mention of complication

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
S81.809A Unspecified open wound, unspecified lower leg, init encntr

SNOMED

262555007 Human bite - wound (disorder)
283705004 Human bite of hand (disorder)
283695002 Human bite of neck (disorder)
283710000 Human bite of trunk (disorder)
283719004 Human bite of lower limb (disorder)

section name header

Basics ⬇

Diagnosis ⬆ ⬇

History

Physical Exam

Lab

Imaging

Other Considerations

Treatment ⬆ ⬇

First Line

Second Line

Follow-Up ⬆ ⬇

Admission Criteria

Discharge Criteria

Geriatric Considerations

Pediatric Considerations

Issues for Referral

Pearls and Pitfalls ⬆ ⬇

Additional Reading ⬆ ⬇

Codes ⬆