Affects: Cats, Dogs
Capnocytophaga canimorsus is a fastidious, slow-growing, Gram-negative rod of the genus Capnocytophaga. It is a commensal bacterium in the normal gingival microbiota of canine and feline species, but can cause illness in humans. Transmission may occur through bites, licks, or even proximity to animals. C. canimorsus generally has low virulence in healthy individuals, but has been observed to cause severe, even grave, illness in persons with pre-existing conditions such as asplenia. The pathogenesis of C. canimorsus is still largely unknown, but increased clinical diagnoses have fostered an interest in the bacillus. Treatment with antibiotics is effective in most cases, but the most important yet basic diagnostic tool available to clinicians remains the knowledge of recent exposure to canines or felines.
Treatment: Immediate cleansing of wounds caused by canines and felines can be successful in keeping C. canimorsus infections at bay. Irrigation of wounds with saline is recommended, and individuals are encouraged to seek medical help for the administration of antibiotics. Antibiotics are recommended if wounds are deep or if individuals postpone seeking medical attention. Antibiotics that contain beta-lactamase inhibitors (i.e., oral Augmentin or parenteral Unasyn) cover C. canimorsus, as well as other organisms common in bites.
Penicillin G is the drug of choice, although some isolates have been found to show resistance. C. canimorsus is susceptible to ampicillin, third-generation cephalosporins, tetracyclines, clindamycin, and chloramphenicol. It has shown resistance to gentamicin. Treatment is recommended for a minimum of three weeks. Hospitalization is required in more severe infections. For cases of sepsis, high doses of penicillin are required. Third-generation cephalosporins are often given before diagnosis because they cover a broad range of Gram-negative bacteria. After diagnosis, provided the strain is not beta-lactamase-producing, medication should be switched to penicillin G. Presumably, penicillin G could be given with a beta-lactamase inhibitor combination, such as Unasyn, for patients with a beta-lactamase-producing strain.
Mortality of meningitis-related infections is much lower than the mortality associated with sepsis. Because C. canimorsus induces fulminant sepsis, earlier diagnosis is associated with greater survival.