What is the recommended antibiotic coverage for dog scratches?

Recommended Antibiotic Coverage for Dog Scratches

Amoxicillin-clavulanate is the first-line antibiotic treatment for dog scratches due to its broad coverage against both aerobic and anaerobic bacteria commonly found in these wounds. 1, 2

Microbiology of Dog Scratch Infections

• Dog scratches can introduce multiple bacteria into the wound, with an average of 5 different bacterial species per wound 1
• Common pathogens include:
  • Pasteurella species (found in 50% of dog bite/scratch wounds) 1
  • Staphylococcus aureus and Streptococcus species (found in ~40% of wounds) 1
  • Anaerobic bacteria including Bacteroides, Fusobacterium, Porphyromonas, Prevotella, and Peptostreptococci 1
  • Capnocytophaga canimorsus (rare but potentially fatal, especially in immunocompromised patients) 1

Antibiotic Recommendations

First-line Oral Therapy:

• Amoxicillin-clavulanate 875/125 mg twice daily 1, 2

Alternative Oral Options:

• Doxycycline 100 mg twice daily (excellent activity against Pasteurella multocida) 1
• Penicillin VK plus dicloxacillin 500 mg four times daily (each) 1
• Moxifloxacin 400 mg daily (good monotherapy with anaerobic coverage) 1

Intravenous Options (for severe infections):

• Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
• Piperacillin-tazobactam 3.37 g every 6-8 hours 1
• Second-generation cephalosporins (e.g., cefoxitin 1 g every 6-8 hours) 1
• Carbapenems (ertapenem, imipenem, meropenem) 1

Antibiotics to Avoid:

• First-generation cephalosporins (e.g., cephalexin) 1
• Penicillinase-resistant penicillins (e.g., dicloxacillin) alone 1
• Macrolides (e.g., erythromycin) 1
• Clindamycin alone (poor activity against Pasteurella multocida) 1

Treatment Algorithm

For Minor Dog Scratches:

1. Clean wound thoroughly with sterile normal saline 1, 2
2. Consider prophylactic antibiotics for 3-5 days if: 1
   • Patient is immunocompromised
   • Patient is asplenic
   • Patient has advanced liver disease
   • Wound is on the hand or face
   • Wound has penetrated periosteum or joint capsule
   • Significant edema is present

For Established Infections:

1. Obtain cultures if possible, especially for treatment-resistant infections 3
2. Start empiric therapy with amoxicillin-clavulanate 1, 2
3. Consider intravenous antibiotics for severe infections or systemic symptoms 1
4. Continue treatment for 7-14 days depending on severity 1

Special Considerations

• Meta-analysis shows prophylactic antibiotics reduce infection risk by 44% in dog bite wounds 4
• Tetanus prophylaxis should be administered if vaccination is not current (within 10 years) 1
• Consider rabies prophylaxis based on consultation with local health officials 1, 2
• Rare pathogens like Serratia marcescens may cause infection in immunocompromised patients 3
• Hand wounds are at higher risk for complications and should be treated more aggressively 1

Common Pitfalls to Avoid

• Failure to recognize the polymicrobial nature of dog scratch infections 1
• Using antibiotics with inadequate coverage against Pasteurella species 1
• Delaying treatment in high-risk patients or high-risk wound locations 1
• Inadequate wound cleaning and irrigation 2
• Not considering unusual pathogens in immunocompromised patients 3