EBQ:Antibiotic prophylaxis for mammalian bites

Complete Journal Club Article
Medeiros I., Saconato H.. "Antibiotic prophylaxis for mammalian bites". Cochrane Database Syst Rev. 2001. 2(CD001738):.
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Clinical Question

Is the use of prophylactic antibiotics for mammalian bites effective in preventing wound infections?


Antibiotic prophylaxis after human bites and bites of the hand may decrease the risk of wound infection but further evidence is needed. No evidence shows effectiveness in the use of antibiotic prophylaxis after cat or dog bites.

Major Points

  • Prophylactic antibiotics were associated with statistically significant reduction of infection rate for the following type of bites:
    • bites by humans
    • bites located on the hand (NNT=4)
  • Prophylactic antibiotics did not appear to reduce rate of infection after bites by cats or dogs
  • Wound type (e.g. lac vs puncture) did not influence effectiveness of prophylactic antibiotics
  • Prevention of tetanus/rabies, together with adequate cleansing of the wounds are the cornerstone of infection prevention in mammalian bites. In select patients, with concerning bite location (e.g. hand) and type of mammal (e.g. human) prophylactic antibiotics may be beneficial

Study Design

  • Systematic review of randomized and quasi-randomized controlled trials
  • Studies were reviewed by two reviewers
  • 8 studies included


Patient Demographics

  • Two studies included only children
  • Two studies included only adults
  • Three studies included both children and adults

Inclusion Criteria

  • RCT's included which studied patient's with mammalian bites
    • Compared abx vs. placebo OR no intervention
    • Ability to determine infection at bite site
  • Patients who present for medical care within 24 hours of bite AND no signs of infection

Exclusion Criteria

  • The studies excluded patients whose bites violated the joint capsule or tendon


  • Of the studies included, patients were randomized to either antibiotics vs. placebo OR no intervention
  • Large antibiotic heterogeneity across the trials:


Primary Outcome

  • When looking at all mammalian bites, prophylactic antibiotics did not significantly reduce the rates of infection (OR 0.49, 95% CI 0.15 to 1.58)

Subgroup analysis

Animal Species

Significant reduction of infection rate shown only in human bite subgroup

  • Human bites: 0% (0/33) for antibiotic group vs. the control group 47% (7/15) (OR 0.02, 95% CI 0.00 to 0.33)
  • Dog Bites: 4% (10/225) for antibiotic group vs to 5.5% (13/238) for control
  • Cat Bites: 0% (0/5) for antibiotic group vs 67% (4/6) for control (included only 1 study with 11 patients)

Wound Type

Wound type did not significantly influence the effect of prophylactic antibiotics

  • Punctures: 7% (1/14) vs 31% (5/16)
  • Lacerations: 3% (2/63) vs 6% (4/66)
  • Avulsions: 5% (2/41) vs 3% (1/30)

Location of Wound

Significant reduction of infection rate was seen in hand bites

  • Hand: 2% in antibiotic group vs 28% in control (OR 0.10, NNT=4)
  • Trunk: Infection occurred in only 1 patient in control group, none in antibiotic group
  • Head/Neck: Infection occurred in only 1 patient in control group, none in antibiotic group
  • Arms: No infection recorded in either group

Criticisms & Further Discussion

  • Significant heterogeneity was observed in the meta-analysis
  • Small number of overall amount of patients, therefore cannot rule out possible beneficial effect of prophylactic antibiotics that was not observed due to study size
  • The antibiotics used in the studies varied significantly, and therefore the effect of antibiotic prophylaxis may have been reduced by inappropriate antibiotic choice [1]
  • Further RCT's are indicated to evaluate the true effectiveness of antibiotic prophylaxis for mammalian bites and specific subgroups which may benefit
  • Beyond antibiotics, the additional question that needs to be answered is primary vs. secondary closure of the wound. Traditional belief has been that while primary closure improves cosmesis, these wounds are particularly dirty and closure may increase infection rate. Recent studies and reviews have challenged this belief, particularly for wounds closed within 8 hours and given ABX's [2]


Funding for Cochrane Review's come from internal sources within the Cochrane Collaboration, primarily from proceeds from The Cochrane Library.

See Also

External Links