Disease resulting from a pathogenic bacterium. Group A streptococcal bacteria (group A strep) are also known as Streptococcus pyogenes and are frequently found in the mouth. Infections caused by this bacteria often involve the throat as in strep throat, which is the most common bacterial throat infection and tends to affect children between the ages of 5 and 15 years. Consequences of strep throat include scarlet fever, the kidney condition poststreptococcal glomerulonephritis, and acute rheumatic fever, which affects the heart after a strep throat infection. A group A streptococcal infection may also cause skin conditions such as impetigo. In rare instances, group A strep may spread below the skin and cause serious soft tissue infections of the muscle. This severe invasion by the strep bacteria, sometimes called “flesh-eating disease,” can cause a person to lose a limb or to develop liver and kidney abnormalities, and it may be even fatal. It is uncertain how or why these deep-tissue infections occur.