Human Oral-Associated Capnocytophaga Species and Their Clinical Relevance

Members of the Capnocytophaga genus are common residents of the oral cavity of humans and some animals, notably dogs and cats. In humans, Capnocytophaga species have received considerably less attention than their canine compatriots due to their more nuanced roles in health and disease. Whilst they are commonly associated with oral health, many aspects regarding their respective functions, inter-species interactions, and activities within oral microbial biofilm communities remain to be established. Furthermore, there are increasing numbers of reports linking certain human oral-associated Capnocytophaga species with systemic infections, suggesting their activities as low-level pathogens. However, clinical data are currently scanty. In this narrative review, we give an overview of human oral-associated Capnocytophaga, including their taxonomy and genomic compositions, challenges in their species-level identification, their colonization patterns within the oral cavity, potential pathogenic features, and their clinical relevance in oral and non-oral infections. We discuss the similarities and differences between key aspects of human and animal oral-associated species of Capnocytophaga, including experimental methods used for their comparative functional analysis.