Capnocytophaga canimorsus
| Capnocytophaga | |
|---|---|
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Bacteroidetes |
| Class: | Flavobacteria |
| Order: | Flavobacteriales |
| Family: | Flavobacteriaceae |
| Genus: | Capnocytophaga |
| Species: |
C. canimorsus Brenner et al., 1989 |
| Binomial name | |
|
Capnocytophaga canimorsus |
|
Capnocytophaga canimorsus is a fastidious, slow-growing Gram-negative rod of the genus Capnocytophaga. It is a commensal bacterium in the normal gingival flora of canine and feline species. Transmission may occur through bites, licks,or even close proximity with animals.C. canimorsus generally has low virulence in healthy individuals, but has been observed to cause severe illness in persons with pre-existing conditions. 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. Very little is known about the pathogenesis of this zoonotic pathogen.
Capnocytophaga canimorsus was first observed in 1976 by Bobo and Newton. The pair isolated a previously unknown Gram-negative bacteria from a patient presenting with meningitis in addition to septicemia. The patient had been previously exposed to two canine bites on two consecutive days from two different dogs. Noting the coincidence between the timing of the bites with the onset of symptoms, Butler et al. analyzed 17 similar cases of patients presenting with either septicemia or meningitis from 1961-1975. The cases had been sent to the CDC for examination due to the presence of an unknown Gram-negative bacillus isolated from infected individuals. Butler notified the CDC of the high incidence of dog bites in connection with the infections. The CDC could not identify the organism and so they applied the name CDC group DF-2. DF-2 stands for Dysgonic fermenter, meaning that the bacteria is a slow-growing, fermentative bacillus. In 1989, while analyzing the properties of the unknown bacteria, Weaver et al. noted many similarities to bacteria of the genus Capnocytophaga. Later that same year, Brenner et al. proposed the name Capnocytophaga canimorsus after examining the morphology, G+C% content and motility of the bacteria.
In the United States, 50% of Americans will be bitten by dogs during the course of their lifetime; 1 million Americans are bitten by dogs annually. Cases of human infection following exposure to C. canimorsus have been observed worldwide. Cases have been reported in the United States, Canada, Europe, Australia and S. Africa. Symptoms may appear within 2–3 days post-exposure, or up to four weeks after. Middle-aged and elderly persons are at greater risk for contraction of disease; more than 60% of sufferers are fifty years of age or older. In addition, individuals who spend a greater portion of their time with canines and felines are also in a higher risk category. This includes veterinarians, breeders, pet owners, and keepers. Having certain pre-existing medical conditions exacerbates the risk. Chance of infection after dog bites varies between three and twenty percent; for cats, it may be as high as 50%.
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