Group A Streptococcus

Group A streptococcus is a Gram-positive coccus that appears to be arranged in chains under the microscope (Streptococcus pyogenes). It is responsible for a number of human diseases such as strep throat (acute pharyngitis) and skin and soft tissue infections such as impetigo and cellulitis. In rare cases, it can cause more serious conditions such as necrotizing fasciitis and streptococcal toxic shock syndrome.