The Streptococcus:
A Brief Introduction to the Streptococci

Streptococcus: chains of nearly spherical bacteria.

The genus Streptococcus is comprised of a wide variety of both pathogenic and commensal gram-positive bacteria which are found to inhabit a wide range of hosts, including humans, horses, pigs and cows. Within the host, streptococci are often found to colonize the mucosal surfaces of the mouth, nares and pharynx. However, in certain circumstances, they may also inhabit the skin, heart or muscle tissue

Pathogenic streptococci of man include S. pyogenes, S. pneumoniae, and S. faecalis. Among the pathogenic hemolytic streptococci, S. pyogenes, or group A streptococci, has been implicated as the etiologic agent of acute pharyngitis ("strep throat"), impetigo, rheumatic fever, scarlet fever, glomerulonephritis, and invasive fasciitis.

A peptidoglycan cell wall, containing muramic acid and glucosamine, is common to all streptococci. Pathogenic streptococci have also been classified into groups according to carbohydrate antigens associated with the cell wall. Group A streptococci may be further subdivided according to the variety of M protein expressed on the cell surface. M protein serotype has also been found to strongly correlate with the disease caused by a particular strain of streptococci.