Streptococcus canis

Streptococcus canis is a group G beta-hemolytic species of Streptococcus. It was first isolated in dogs, giving the bacterium its name. These bacteria are characteristically different from Streptococcus dysgalactiae, which is a human-specific group G species that has a different phenotypic chemical composition. S. canis is important to the skin and mucosal health of cats and dogs, but under certain circumstances, these bacteria can cause opportunistic infections. These infections were known to afflict dogs and cats prior to the formal description of the species in Devriese et al., 1986. However, additional studies revealed cases of infection in other mammal species, including cattle and even humans. Instances of mortality from S. canis in humans are very low with only a few reported cases, while actual instances of infection may be underreported due to mischaracterizations of the bacteria as S. dysgalactiae. This species, in general, is highly susceptible to antibiotics, and plans to develop a vaccine to prevent human infections are currently being considered.

The four serogroups of hemolytic streptococci identified in domesticated dogs belong to Lancefield groups A, C, E, and G. Of these four, S. canis is described as belonging to group G due to it being a beta-hemolytic and aesculin-negative Streptococcus that is able to ferment lactose. These bacteria are known to be part of the natural flora of the respiratory tract of cats and dogs. This bacterium was originally isolated from dogs, and has been differentiated from S. dysgalactiae, which is the group G Streptococus of human origin. S. canis is known to infect a variety of mammal species, including dogs, cats, mink, mice, rabbits, foxes, cattle, and even humans.