The Genus Streptococcus – Part I: Emerging Pathogens in the “Pyogenic Cocci” and the “Streptococcus bovis” Groups

Abstract

In this first part of a two-part update on the streptococci, new and emerging pathogens in the “pyogenic cocci group” and the “Streptococcus bovis group” are addressed. Among the pyogenic cocci, several new species have been described, and some of these are becoming relevant agents of human disease. Streptococcus porcinus and Streptococcus pseudoporcinus are β-hemolytic streptococci that are found in swine and humans, respectively. S. pseudoporcinus has been isolated primarily from the female genital tract and may play a role in genitourinary tract infections, wound infections, and adverse pregnancy outcomes. Streptococcus iniae, Streptococcus hongkongensis, and Streptococcus ictaluri are fish pathogens, and S. iniae, in particular, has been isolated from several human infections in persons who handle raw seafood or experience penetrating injuries from fish spines or crab pincers. Streptococcus gallolyticus subspecies (i.e., the former “S. bovis group”) are well-recognized causes of bacteremia, meningitis, and endocarditis. S. gallolyticus subsp. gallolyticus is known to be associated with colon cancer, and current studies suggest that other S. gallolyticus subspecies (particularly S. gallolyticus subsp. pasteurianus) may also be associated with meningitis and other digestive tract malignancies. In this review, current research on S. gallolyticus subspecies and proposed mechanisms for their involvement in the pathogenesis of colonic carcinoma are also briefly addressed.