70,000X magnification electron

70,000X magnification electron micrograph of an ultra-thin section of Streptococcus pyogenes. Image source: Dr. Vincent A. Fischetti, Rockefeller University.

Streptococcus is a genus of spherical or oval bacteria that grow in pairs or bead-like chains. Although some species of streptococci are harmless, others are responsible for many common infections, including strep throat, tonsillitis, scarlet fever, impetigo, cellulitis, erysipelas, and puerperal fevers. A related organism is a common cause of pneumonia and one type may cause endocarditis in damaged heart valves.


Penicillin is the antibiotic of choice.


Rheumatic fever and Bright's disease are late immune responses to Streptococcus.