Antibiotic prophylaxis for mammalian bites

Bites by mammals are a common problem and they account for up to 1% of all visits to hospital emergency rooms. Dog and cat bites are the most common and people are usually bitten by their own pets or by an animal known to them. School-age children make up almost a half of those bitten. Prevention of tetanus, rabies and wound infection are the priorities for staff in emergency rooms. The use of antibiotics may be useful to reduce the risk of developing a wound infection.

To determine if the use of prophylactic antibiotics in mammalian bites is effective in preventing bite wound infection.

Relevant RCTs were identified by electronic searches of MEDLINE, EMBASE, LILACS and the Cochrane Controlled Trials Register databases in November 2000.

We included randomised controlled trials which studied patients with bites from all mammals. Comparisons were made between antibiotics and placebo or no intervention. The outcome of interest was the number of infections at the site of bite.

Two reviewers extracted the data independently. All analyses were performed according to the intention-to-treat method.

Eight studies were included. The use of prophylactic antibiotics was associated with a statistically significant reduction in the rate of infection after bites by humans. Prophylactic antibiotics did not appear to reduce the rate of infection after bites by cats or dogs. Wound type, e.g. laceration or puncture, did not appear to influence the effectiveness of the prophylactic antibiotic. Prophylactic antibiotics were associated with a statistically significant reduction in the rate of infection in hand bites (OR 0.10, 95% CI 0.01 to 0.86; NNT = 4, 95% CI 2 to 50).

There is evidence from one trial that prophylactic antibiotics reduces the risk of infection after human bites but confirmatory research is required. There is no evidence that the use of prophylactic antibiotics is effective for cat or dog bites. There is evidence that the use of antibiotic prophylactic after bites of the hand reduces infection but confirmatory research is required.