Doxycycline Effectiveness Against Pasteurella multocida
Doxycycline is an effective alternative antibiotic for treating Pasteurella multocida infections, particularly in patients who cannot tolerate penicillins, though amoxicillin-clavulanate remains the preferred first-line agent for animal bite wounds where P. multocida is commonly encountered.
Primary Treatment Recommendations for P. multocida Infections
Animal Bite Wounds (Most Common Context)
Amoxicillin-clavulanate is the first-line empirical therapy for dog and cat bite wounds, which frequently harbor P. multocida (isolated from 50% of dog bites and 75% of cat bites) 1.
Doxycycline serves as a recommended alternative oral agent when amoxicillin-clavulanate cannot be used, alongside penicillin VK plus dicloxacillin 1.
For penicillin-allergic patients specifically, doxycycline 100 mg orally twice daily is a preferred alternative with good activity against P. multocida, staphylococci, and anaerobes 2.
Agents to Avoid
- First-generation cephalosporins (cephalexin), penicillinase-resistant penicillins (dicloxacillin), macrolides (erythromycin), and clindamycin all have poor in vitro activity against P. multocida and should be avoided 1.
Evidence Supporting Doxycycline Efficacy
In Vitro and Clinical Data
Doxycycline demonstrates excellent in vitro activity against P. multocida, with MIC90 values of ≤2.0 μg/mL, comparable to penicillin and other highly effective agents 3.
In experimental animal models, doxycycline at 10 mg/kg body weight for 5 days reduced mortality from 90% to 5-30% in P. multocida-infected broiler chickens, demonstrating high therapeutic efficacy 4.
Clinical experience supports doxycycline as highly effective against P. multocida respiratory infections, particularly in elderly patients with underlying lung disease 5.
Veterinary Context
For avian patients with P. multocida infection following cat bites, doxycycline is specifically recommended as the treatment of choice 6.
Antimicrobial susceptibility testing of P. multocida isolates from swine and poultry shows variable resistance patterns, with some strains demonstrating resistance to tetracyclines, though newer agents like enrofloxacin and cefquinome maintain excellent activity 7.
Clinical Algorithm for Antibiotic Selection
For Established Animal Bite Infections:
First choice: Amoxicillin-clavulanate 875/125 mg orally twice daily for 7-10 days 1, 2
If penicillin allergy: Doxycycline 100 mg orally twice daily for 7-10 days 1, 2
Alternative: Moxifloxacin 400 mg daily (provides monotherapy including anaerobic coverage) 2
For severe infections requiring IV therapy: Ampicillin-sulbactam 1.5-3.0 g IV every 6 hours or carbapenems 1, 2
For Respiratory P. multocida Infections:
- Penicillin remains the preferred drug, but doxycycline is highly effective as an alternative 5
Important Clinical Caveats
Doxycycline can be used safely in children ≥2 years old when given for durations less than 2 weeks 1, though this applies to other indications and should be weighed against alternative options for bite wounds.
The polymicrobial nature of bite wounds (average of 5 bacterial types per wound, 60% yielding mixed aerobic and anaerobic bacteria) necessitates broad-spectrum coverage 1.
Resistance patterns vary geographically and by animal source, so local susceptibility data should inform treatment decisions when available 7.
Wounds presenting >8-12 hours after injury typically have established infection requiring full treatment courses rather than prophylaxis 1.
Tetanus prophylaxis should be administered if not received within 10 years 2.