Infectious Disease Compendium

Cat Bite

Diagnosis

"I was bit by a cat".

Epidemiologic Risks

Kitty kitty kitty nice kitty kitty, damn it, it bit me in the hand.

Microbiology

S. aureus, streptococci, anaerobes and Pasteurella.

When tested by 16S ribosome methodology the wounds are filled with difficult to grow anaerobes, that, when grown, are ampicillin susceptible (Pubmed).

Empiric Therapy

Amoxicillin-clavulanic acid for prophylaxis, for real infections use real antibiotics directed against the flora of the cat mouth. Ampicillin or third generation cephalosporins PLUS metronidazole would be good choices. If PCN allergic use a quinolone PLUS (clindamycin OR metronidazole) OR doxycycline alone. Pasteurella are usually resistant to first generation cephalosporins.

Specific Therapy

Debride, then prophylaxis for 10 days. And don't forget the tetanus booster. You did, didn't you? Soft tissue infections (cellulitis or abscess) is iv until afebrile, then po for a total of 10-14 days. Septic arthritis or tenosynovitis is 2 -3 weeks of iv. Osteomyelitis is usually 6 weeks of iv.

Pearls

Cats teeth are like needles and inject bacteria deep into tissue. This makes debridement difficult if not impossible and makes joint infections likely. They say that Pasteurella infections start in the first 48 hours after the bite and that staphylococcal and mixed infections take longer to manifest.

The majority of patients after a scratch will have symptoms (fatigue, arthralgias and myalgias, half of patients will seroconvert and maybe a quarter will have evidence of a blood stream infection (PubMed).

Rants

Cats really are vermin that serve no useful purpose but spread disease.  And.  Some epidemiologic data suggest cat scratches and bites increase the risk of depression (PubMed).  I'd be depressed if I had to own a cat.