The bacteriology of dog bite wounds on initial presentation

Area of Science:

• Microbiology
• Infectious Diseases
• Emergency Medicine

Background:

• Open dog bite wounds represent a significant clinical challenge due to the risk of infection.
• Understanding the microbial landscape of these wounds is crucial for effective treatment strategies.

Purpose of the Study:

• To characterize bacterial isolates from open dog bite wounds.
• To assess the utility of Gram stains in guiding antibiotic selection.
• To identify differences in bacterial flora between infected and uninfected wounds.

Main Methods:

• Prospective study of 420 patients presenting with open dog bite wounds.
• Collection of wound samples for Gram stains, aerobic and anaerobic cultures, and antibiotic sensitivity testing.
• Analysis of bacterial isolates and comparison between clinically infected and uninfected wounds.

Main Results:

• 48% of wounds showed no bacterial growth; Staphylococcus epidermidis was the most frequent isolate (20.5%).
• Clinically infected wounds often contained multiple pathogenic organisms (50%), with Enterobacteria, Pseudomonas, and Staphylococcus aureus being predominant.
• Gram stains were minimally useful for specific antibiotic therapy selection (6% in infected wounds).
• Significant differences in bacterial types and frequency were observed between infected and uninfected wounds.

Conclusions:

• While many dog bite wounds are sterile, infected wounds frequently involve polymicrobial infections.
• Cephradine demonstrated high efficacy (>95%) in treating clinical infections.
• Broad-spectrum antibiotics like cephalosporins or penicillinase-resistant penicillins are effective for complex infections.
• Aminoglycosides may be required for a small percentage (6%) of isolates.