What IV antibiotic is appropriate for a pregnant woman with a worsening cat bite infection on her hand, currently on amoxicillin-clavulanic acid (Augmentin), with signs of cellulitis and potential abscess formation?

IV Antibiotic Selection for Pregnant Woman with Worsening Cat Bite Infection

For a pregnant woman with a worsening cat bite infection on the hand despite oral amoxicillin-clavulanate therapy, ampicillin-sulbactam (1.5-3.0g IV every 6 hours) is the most appropriate IV antibiotic to initiate.

Clinical Assessment and Rationale

The patient presents with:

• Cat bite to the thenar eminence with worsening symptoms despite oral amoxicillin-clavulanate
• Signs of progressive infection: increasing pain, swelling, redness
• Induration at the bite site
• Erythematous streaks extending to the forearm (lymphangitis)
• Low-grade fever (100.8°F)
• Positive pregnancy test

Antibiotic Selection Algorithm for Cat Bite Infections in Pregnancy:

1. First-line IV therapy for pregnant women with cat bites: Ampicillin-sulbactam

   • Provides excellent coverage against typical cat bite pathogens including Pasteurella multocida
   • Safe in pregnancy
   • Recommended dosage: 1.5-3.0g IV every 6 hours 1

2. Alternative options if beta-lactam allergy exists:

   • Cefazolin (if non-severe penicillin allergy): 1g IV every 8 hours
   • Ceftriaxone: 1-2g IV every 24 hours (with metronidazole for anaerobic coverage)

3. Antibiotics to avoid in pregnancy:

   • Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) 1
   • Tetracyclines (doxycycline) 1
   • Aminoglycosides (tobramycin) should be avoided if possible due to risk of ototoxicity 2

Microbiology of Cat Bites

Cat bites require coverage for:

• Pasteurella multocida (present in 50-80% of cat bites)
• Streptococcus species
• Staphylococcus species (including MRSA consideration)
• Anaerobes

Special Considerations in Pregnancy

Pregnancy significantly impacts antibiotic selection:

• Fluoroquinolones are contraindicated due to potential teratogenic effects 1
• Tetracyclines should be avoided during pregnancy 1
• Beta-lactams (penicillins, cephalosporins) have excellent safety profiles in pregnancy

Management Pearls

• Orthopedic consultation is essential given the location of the bite (hand) and signs of advancing infection
• The thenar eminence location is concerning for potential deep space infection
• Lymphangitis (red streaks) indicates progression beyond localized infection
• Failure of oral amoxicillin-clavulanate necessitates IV therapy and possible surgical evaluation
• Hand infections can rapidly progress to compartment syndrome, tenosynovitis, or osteomyelitis

Common Pitfalls to Avoid

1. Underestimating cat bite severity: Cat bites create deep puncture wounds that can inoculate bacteria into tendon sheaths, joints, or bones.

2. Inadequate anaerobic coverage: While Pasteurella is the predominant organism, anaerobes are also common in cat bites.

3. Using fluoroquinolones in pregnancy: Despite excellent coverage against Pasteurella, fluoroquinolones should be avoided in pregnancy 1.

4. Delaying orthopedic consultation: Hand infections, especially in the thenar space, can rapidly compromise function and require surgical intervention.

5. Inadequate duration of therapy: Even after clinical improvement, a full course (typically 10-14 days) is necessary to prevent relapse.