Streptococcus is a genus of spherical, Gram-positive bacteria of the phylum Firmicutes. These bacteria grow in chains or pairs, with cell division occurring only along one axis. In this sense they are contrasted with Staphylococcus, which divides along several axes, generating a "cluster" of cells, which resemble clusters of grapes.

Members of the genus Streptococcus which cause disease include:

• Group A Streptococci (Streptococcus pyogenes) which causes Group A streptococcal infection
• Group B Streptococci (Streptococcus agalactiae), also known as GBS, which causes meningitis in neonates and the elderly, with occasional systemic bacteremia. They can also colonise the female reproductive tract, increasing the risk for premature rupture of membranes and transmission to the child. The Centers for Disease Control and Prevention (CDC) have a website dedicated to GBS: Preventing Group B Strep Disease (http://www.cdc.gov/groupbstrep/)
• Group D Streptococci (S. durans, S. avium, S. bovis)
• Streptococcus pneumoniae which can cause pneumonia
• Streptococcus viridans group which cause endocarditis and dental abscesses.

Transmission

Streptococcus are part of the normal flora of the mouth, skin, intestine and upper respiratory tract of humans.

Specific strains or species can be transmitted in several ways:

• Physical contact
• Using the same eating and drinking utensils as someone who has the bacteria
• Coughing, sneezing, or breathing on someone
• Touching the same doorknobs, faucets, etc.