Capnocytophaga canimorsus

Background

Microbiology

• Gram-negative bacillus in the genus Capnocytophaga
• May be fusiform and curved
• Grows slowly on standard media
• Capnophilic, preferring high CO₂
• Oral flora of dogs (60-70%) and cats (15-55%)

Risk Factors

• Risk factors for severe disease include asplenia and alcoholism

Clinical Manifestations

• Infections usually occur after penetrative inoculation from a dog bite or by exposure of membranes or wounds to saliva
  • Exposures include close petting, kissing, minor scratches, licking of abrasions, licking of intact skin

Bacteremia

• Symptoms associated with bacteremia include fever, diarrhea, abdominal pain, vomiting, headache, and confusion
• A rash is present in 20 to 40%, which can vary from macular or maculopapular rash on trunk and extremities, to purpura fulminans
• Mortality with bacteremia is 15 to 30%

Meningitis

• Headache, fever, neck stiffness, and altered mental status

Other Sites

• Endocarditis is rare, but high mortality around 25%
• Case reports of brain abscess, spinal epidural abscess, eye infections, bone and joint infections, cellulitis, glomerulonephritis, and pneumonia

Management

• Highly susceptible to meropenem, imipenem, piperacillin-tazobactam, amoxicillin-clavulanic acid, and tigecycline
• May be susceptible to ciprofloxacin, clindamycin, erythromycin, tetracycline, aztreonam
• Often resistant to gentamicin, vancomycin, polymyxin B, trimethoprim, ceftazidime, cefotaxime, and amoxicillin