what is caused by streptococcus bacteria
Strep throat is caused by streptococcal (strep) bacteria, most often by group A beta-hemolytic streptococcus (GABS). Other types of strep that can sometimes infect the throat are groups C and G strep bacteria. A strep infection causes the throat (pharynx) and the tonsils or adenoids to become irritated, inflamed, and painful.