Final answer:
Streptococcus is a genus of bacteria responsible for various infections such as strep throat, scarlet fever, and necrotizing fasciitis, primarily caused by Streptococcus pyogenes, a group A streptococcus.
Step-by-step explanation:
Streptococcus, a genus of bacteria, can cause several different types of infections in humans. One of the most well-known species is Streptococcus pyogenes, which falls under Lancefield group A streptococci (GAS). This bacteria is the causative agent of a variety of diseases including pharyngitis (strep throat), scarlet fever, impetigo, and necrotizing fasciitis (flesh-eating disease).
Some strains of group A streptococci produce an erythrogenic toxin leading to scarlet fever, which presents as a disseminated fine red rash on the skin and a red rash on the tongue (strawberry tongue). In more severe cases, it may progress to streptococcal toxic shock syndrome (STSS), which can be fatal. Moreover, infections with S. pyogenes can sometimes spread to other body parts and develop into necrotizing fasciitis.