Dog bites: When should you use prophylactic antibiotics?

Dog bites are the most common mammalian bite injury seen in the United States, followed by cat bites and human bites.  Management of minor dog bite wounds includes copious irrigation with normal saline (>150 mL through an 18 or 19 gauge plastic catheter), debridement of any devitalized or crushed tissue, assessment for underlying tendon or bone injury, updating tetanus status when indicated, and assessment of rabies risk.  Primary closure of bite wounds is controversial, but it is generally accepted that wounds can be sutured unless they are high risk or already infected.  High risk wounds should be closed with delayed primary closure 72 hours later.  Wounds to the face are usually sutured for optimal cosmetic results, and infection is rare due to copious irrigation, excellent blood supply, and use of antibiotic prophylaxis.

There is a lack of consensus about which type of wounds require antibiotic prophylaxis.  Risk factors for infection include location on hand, foot, or over a major joint, puncture wounds and crush injuries, treatment delay > 12 hours, and systemic factors such as advanced age, immunosuppression, asplenism, diabetes, and vascular disease.  Griego et al list the following indications for prophylactic antibiotics:

There is no clear consensus on the appropriate antibiotic choice for infection prophylaxis.  When infections do develop from dog bites, they are usually polymicrobial with both aerobic and anaerobic species.  Staphylococcus, Streptococcus, and Corynebacterium are the most common aerobic species isolated, with Bacteriodes fragilis, Prevotella, Peptostreptococcus, and Fusobacterium among common anaerobic isolates.  A rare, but potentially fatal infection associated with dog bites is Capnocytophaga canimorsus. Patients who develop this infection usually have a predisposing condition, such as splenectomy.

Amoxicillin/clavulanate is often prescribed due its dual aerobic and anaerobic coverage. Alternative regimens include clindamycin plus ciprofloxacin, TMP/SMX, and second- or third-generation cephalosporins such as cefuroxime.  Duration should be 5-7 days.  It is recommended that patients have an initial follow-up visit at 24-48 hours to assess wound healing and presence of infection.





References:
1.  Griego RD et al.  Dog, cat, and human bite wounds:  A review.  J Am Acad Dermatol 1995;33:1019-29.
2. Smith PF, Meadowcroft AM, May DB.  Treating mammalian bite wounds.  Journal of Clinical Pharmacy & Therapeutics.  2000;25:85-99