[3] C. canimorsus generally has low virulence in healthy individuals,[4] but has been observed to cause severe, even grave, illness in persons with pre-existing conditions.

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.

The pair isolated a previously unknown Gram-negative bacterium from a patient presenting with meningitis in addition to sepsis.

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 sepsis or meningitis from 1961 to 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.

In 1989, while analyzing the properties of the unknown bacterium, 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 species.

[4] The name Capnocytophaga is derived from the Greek word kapnos, meaning "smoke", and given here because of its dependence on carbon dioxide for growth.

[6] Significant dog bites affect tens of millions of people globally each year, and cases of human infection following exposure to C. canimorsus have been observed worldwide.

Middle-aged and elderly persons are at greater risk for contraction of disease; more than 60% of sufferers are 50 years of age or older.

[2] The genome of C. canimorsus strain Cc5 consists of a single circular chromosome of 2,571,406 bp with a G+C content of 36.11%, and it encodes 2,405 open reading frames.

Clinical manifestations of C. canimorsus in rabbits causes a range of symptoms, including disseminated intravascular coagulation, cellular necrosis (tissue death), low blood pressure, gangrene, and kidney failure.

[10] In addition to those at higher risk of developing complications from C. canimorsus due to greater contact with felines and canines, certain pre-existing conditions place individuals in a critically high-risk category.

Because this particular pathogen seems to flourish in asplenic patients, both IgM antibodies and tuftsin may be critical in the process of marking this bacterium for destruction by phagocytosis.

[4] Asplenics often have double the amount of healthy iron in their bloodstreams, and are 60 times more at risk of developing fatal clinical manifestations of the bacterium.

Individuals often complain of any combination of: fever, vomiting, diarrhea, malaise, abdominal pain, myalgia, confusion, dyspnea, headaches, and skin rashes such as exanthema.

[4] Due to the relatively slow growth of this bacterium, diagnosis often relies upon the clinician having knowledge that the patient was previously in contact with a canine or feline.

Once aware of this, clinicians can request that agar plates be kept longer than one week to ensure proper isolation of the bacterium.

Cases have been noted where cultures repeatedly came up negative for C. canimorsus, only to determine its presence with 16S rRNA gene sequencing.

Antibiotics that contain beta-lactamase inhibitors (i.e., oral Augmentin or parenteral Unasyn) cover C. canimorsus, as well as other organisms common in bites.

[17] In the presence of C. canimorsus, cytokine activity is greatly downregulated, because the macrophages fail to produce TNF-α, IL-8, IL-6 and IL-1α, interferon-γ, and nitric oxide.

[12] In addition, toll-like receptor 4 (TLR4) normally recognizes pathogens and begins a signalling cascade to induce production of proinflammatory cytokines via the NF-κB pathway.

In cells infected with C. canimorsus, TLR4 did not activate the signalling pathway, so did not elicit an inflammatory response by the immune system.

[17] Because this species does not elicit a strong inflammatory response, the bacteria have ample time for replication before detection by the host immune system.

[12] Electron micrographs of J774.1 monolayers infected with C. canimorsus have shown cells of the bacteria within the macrophage's vacuoles, surrounded by bacterial septa.