Capnocytophaga canimorsus
Classification
Domain: Bacteria; Phylum: Bacteroidetes; Class: Flavobacteriia; Order: Flavobacteriales; family: Flavobacteriaceae
Species
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NCBI: [1] |
Capnocytophaga canimorsus
Description and Significance
Capnocytophaga canimorsus is a Gram-negative, rod-shaped bacterium commonly found in the oral cavities of dogs and cats. While harmless to animals, it can cause opportunistic infections in humans, typically following bites or scratches. These infections can be severe, including conditions like sepsis and meningitis, in individuals with a weak immune system or pre-existing health conditions. Understanding C. canimorsus is important for addressing the spread of zoonotic diseases and learning how to properly treat these infections.
Genome Structure
The genome of Capnocytophaga canimorsus consists of a single, circular chromosome that is approximately 2.8 million base pairs long, with 36.11% of its content being guanine and cytosine. It additionally contains 2,405 CDSs. The genome size of C. canimorsus is most similar to Capnocytophaga ochracea, a bacteria found in the mouths of dogs and cats since it has 2.6 million base pairs. C. canimorsus contains 206 lipoprotein genes which is unusually high among Eubacteria and encodes the LolACDE lipoprotein export system to help transport these lipoproteins.
The genome does not encode type III, IV, or VI secretion systems which are commonly linked to pathogenesis. However, it does produce the enzyme protease, CcDPP7, which causes factor X dysfunction by N-terminal cleavage and promotes immune evasion and triggers hemorrhage.
Cell Structure, Metabolism and Life Cycle
Capnocytophaga canimorsus is a thin, gram-negative, facultatively anaerobic bacterium with elongated, filamentous cells. Its cell wall is composed of lipopolysaccharides and peptidoglycan, which contribute to its cell structure and interactions with host environments. C. canimorsus also has multiple flagella that enable motility. C. canimorsus gains energy through respiratory metabolism, making it capable of metabolizing various organic compounds. It is chemoorganotrophic, meaning it uses organic molecules as both carbon sources and electron donors for energy production. The bacterium can perform aerobic respiration when oxygen is present but can also survive in low-oxygen environments, demonstrating metabolic flexibility. C. canimorsus produces several significant molecules, including lipopolysaccharides and proteases that contribute to its pathogenicity. C. canimorsus has the ability to generate endotoxins that trigger strong inflammatory responses in humans. C. canimorsus also produces adhesion molecules that facilitate its attachment to host cells, which is critical for its potential to cause serious infections, especially in immunocompromised individuals.
Ecology and Pathogenesis
Capnocytophaga canimorsus is a gram-negative, facultatively anaerobic bacterium primarily found in the oral microbiota of dogs and cats. Its natural habitat is the oral cavity of these animals, where it typically exists as a commensal organism. This bacterium is part of the complex microbial ecosystem of animal mouths, living symbiotically without causing harm to its host. C. canimorsus plays a role in the oral microbiome's ecological balance. While its specific contributions to broader environmental processes are not extensively documented, its presence in animal oral ecosystems suggests it participates in microbial interactions and potentially contributes to nutrient cycling within these microenvironments. Regarding disease potential, C. canimorsus can cause serious and potentially life-threatening infections in humans, particularly in immunocompromised individuals, those without a spleen, or individuals with underlying health conditions. Transmission typically occurs through dog or cat bites, scratches, or close contact with animal saliva. The bacterium can enter human bloodstreams and cause severe systemic infections. Virulence factors of this microbe include the ability to evade immune system detection, the capacity to adhere to and invade human cells, and the production of enzymes that facilitate bacterial spread. Specific patient symptoms might involve a rapidly escalating fever, chills, muscle aches, potential skin lesions or necrotic tissue, potential shock syndrome, and potential respiratory distress. While the infections are rare, they can progress extremely quickly and have mortality rates up to 30 to 50% if not promptly recognized and treated with appropriate antibiotics and supportive medical interventions.
References
Abril, M., Barnett, A., Wegermann, K., Fountain, E., Strand, A., Heyman, B., et al. (2016). Diagnosis of capnocytophaga canimorsus sepsis by whole-genome next-generation sequencing. Open Forum Infectious Diseases. 3(3).
Cornelis, G., Landmann, R., Mally, M., Paroz, C., & Shin, H. (2008). Capnocytophaga canimorsus: A Human Pathogen Feeding at the Surface of Epithelial Cells and Phagocytes. National Library of Medicine.
Fischer, L., Weyant, R., White, E., Quinn, F. (1995). Intracellular multiplication and toxic destruction of cultured macrophages by Capnocytophaga canimorsus. Infection and Immunity. 63 (9): 3484–3490.
Hack, K., Renzi, F., Hess, E., Lauber, F., Douxfils, J., Dogné, J. M., & Cornelis, G. (2017). Inactivation of human coagulation factor X by a protease of the pathogen Capnocytophaga Canimorsus. Journal of Thrombosis and Haemostasis. 15(3):487-499.
Janda, J., Graves, M., Lindquist, D., & Probert, W. (2006). Diagnosingcapnocytophaga canimorsusinfections. Emerging Infectious Diseases. 12(2): 340-342.
Le Moal G., Landron C., Grollier G., Robert R., Burucoa C. (2003). Meningitis Due to Capnocytophaga canimorsus after Receipt of a Dog Bite: Case Report and Review of the Literature. Clinical Infectious Diseases. 36 (3): e42-e46.
Manfredi, P., Pagni, M., & Cornelis, G. (2011). Complete genome sequence of the dog commensal and human pathogen capnocytophaga canimorsus strain 5. Journal of Bacteriology. 193(19): 5558-5559.
Mavrommatis, K., Gronow, S., Saunders, E., Land, M., Lapidus, A., Copeland, A., et al. (2009). Complete genome sequence of capnocytophaga ochracea type strain (VPI 2845t). Standards in Genomic Sciences. 1(2): 101-109.
Author
Page authored by Preston Meehl & Leah Crutchfield, students of Prof. Bradley Tolar at UNC Wilmington.
