Streptococcus (family Streptococcaceae) A genus of Gram-positive, non-motile bacteria in which the cells are spherical to ovoid, and often occur in pairs or chains. There are many species, found chiefly as parasites and pathogens in warm-blooded animals, including humans. The genus includes the causal agents of tonsillitis and scarlet fever (S. pyogenes), pneumonia (S. pneumoniae), and dental caries (e.g. S. mutans). Not all species are harmful; some are used in the manufacture of certain dairy products, e.g. yoghurt and butter. (These latter organisms are now regarded as belonging to a separate genus, Lactocossus.)

strep·to·coc·cus / ˌstreptəˈkäkəs/ • n. (pl. streptococci / -ˈkäksī; -sē/ ) a bacterium of a genus (Streptococcus) that includes the agents of souring of milk and dental decay, and hemolytic pathogens causing various infections such as scarlet fever and pneumonia.DERIVATIVES: strep·to·coc·cal / -ˈkäkəl/ adj.

Streptococcus (strep-toh-kok-ŭs) n. a genus of Gram-positive nonmotile spherical bacteria occurring in chains. Most species are saprophytes, but some are pathogenic. Haemolytic streptococci destroy red blood cells in blood agar and are the cause of many infections, including bacterial endocarditis (α-haemolytic strains) and scarlet fever (β-haemolytic strains). S. pneumoniae see pneumococcus. See also Lancefield classification, streptokinase.
—streptococcal adj.

streptococcus Genus of gram-positive spherical or oval bacteria that grow in pairs or bead-like chains. They live mainly as parasites in the mouth, respiratory tract and intestine. Some are harmless but others are pathogenic, causing scarlet fever and other infections. Treatment is with antibiotics.

Streptococcus A genus of spherical Gram-positive bacteria occurring widely in nature, typically as chains or pairs of cells. Many are saprotrophic and exist as usually harmless commensals inhabiting the skin, mucous membranes, and intestine of humans and animals. Others are parasites, some of which cause diseases, including scarlet fever (S. pyogenes; group A streptococci), endocarditis (S. viridans), and pneumonia (S. pneumoniae).