What is the preferred antibiotic for a cat bite?

Preferred Antibiotic for Cat Bite Infections

Amoxicillin-clavulanate is the first-line antibiotic treatment for cat bite infections due to its excellent coverage against Pasteurella multocida and other common pathogens found in cat bite wounds. 1

Microbiology of Cat Bite Wounds

• Cat bites contain an average of 5 different bacterial species per wound, including both aerobic and anaerobic bacteria 2, 1
• Pasteurella multocida is the predominant pathogen, found in approximately 75% of cat bite wounds 1, 3
• Staphylococci and streptococci are present in about 40% of cat bites 2, 1
• Anaerobes are present in 65% of cat bites, including Bacteroides species, fusobacteria, Porphyromonas species, and peptostreptococci 2, 1

First-Line Oral Treatment Options

• Amoxicillin-clavulanate (875/125 mg twice daily for adults) is the recommended first-line therapy based on clinical studies and guidelines 2, 1
• Doxycycline (100 mg twice daily) is an alternative with excellent activity against P. multocida, though some streptococci may be resistant 2, 1
• Penicillin VK plus dicloxacillin (500 mg four times daily for each) can be used as another alternative oral option 1

Antibiotics to Avoid for Cat Bites

• First-generation cephalosporins (e.g., cephalexin) should be avoided due to poor activity against P. multocida 2, 1
• Penicillinase-resistant penicillins alone (e.g., dicloxacillin) should be avoided 2, 1
• Macrolides (e.g., erythromycin) should be avoided due to poor activity against P. multocida 2, 1
• Clindamycin alone is not recommended as it has poor activity against P. multocida 2, 1

Intravenous Treatment Options

For severe infections requiring parenteral therapy:

• Ampicillin-sulbactam (1.5-3.0 g every 6-8 hours) is a recommended intravenous option 2, 1
• Piperacillin-tazobactam (3.37 g every 6-8 hours) is effective for more severe infections 1
• Second-generation cephalosporins (e.g., cefoxitin 1 g every 6-8 hours) are appropriate intravenous options 1
• Carbapenems (e.g., ertapenem, imipenem, meropenem) can be used for severe infections 1

Treatment Duration and Special Considerations

• Standard uncomplicated infections typically require 7-10 days of antibiotic therapy 2
• Osteomyelitis, a potential complication of cat bites, requires 4-6 weeks of antibiotic therapy 1
• Septic arthritis/synovitis requires 3-4 weeks of antibiotic therapy 1
• Cat bites have a higher risk of infection (20-80%) compared to dog bites (3-18%) 3
• Cat bites on the hand have the greatest risk of infection and complications 4

Clinical Pearls and Pitfalls

• Despite the high prevalence of P. multocida in cat bites, it remains highly susceptible to penicillin and its derivatives, making amoxicillin-clavulanate a reliable choice 3
• Failure to treat cat bite wounds appropriately can lead to serious complications, including tendonitis, septic arthritis, osteomyelitis, and rarely endocarditis 1, 5
• Always obtain both aerobic and anaerobic cultures in infected cat bite wounds to guide antibiotic therapy if empiric treatment fails 6
• Patient compliance with the full course of antibiotics is crucial to prevent treatment failure and complications 5
• Tetanus prophylaxis should be administered if vaccination status is outdated or unknown 1, 4