Pathogenicity factors in group C and G streptococci

The pyogenic streptococci of Lancefield groups C and G were initially recognized as a cause of animal infections long before they were even considered as agents of human disease, even though they are widely distributed in animals and humans. They comprise a heterogeneous complex of streptococcal species that act as causative agents of a spectrum of diseases ranging from mild pharyngitis to skin infection to life-threatening systemic infections associated with high mortality rates. In this article we provide an overview of the various group C and group G streptococcal species, the diseases they cause, and the major pathogenicity factors that contribute to their virulence (Table 1).