Group A streptococcal, or GAS, bacteria are often found on the skin and in the throat of healthy individuals. Most of the time, GAS bacteria cause no symptoms at all. At other times, these bacteria affect various parts of the body and cause an infection. Strep throat is the most common of the GAS infections. Impetigo , for example, causes an infection of the top skin layers .
Cellulitis is a more serious infection that involves deeper skin layers and underlying tissue.
Pneumonia is a lung infection, and septic arthritis attacks joints. Some GAS infections, especially blood infections, can be severe. These infections can be associated with streptococcal toxic shock syndrome . In this syndrome, blood pressure drops. The liver, kidney, lungs, and clotting system fail to work properly.