The most likely cause of glomerulonephritis following streptococcal sore throat is Streptococcus pyogenes. This is the only species in the Group A streptococci, and is characterized by beta hemolysis and inhibition by the antibiotic bacitracin. Streptococcus pyogenes sore throat can also be followed by rheumatic fever. Streptococcus pneumoniae is an example of an alpha hemolytic streptococcus that is lysed by optochin (1st Choice). Streptococcus mutans is an example of an alpha hemolytic streptococcus that is not lysed by optochin (2nd Choice). Enterococcus faecalis is an example of a beta hemolytic streptococcus that can grow in 40% bile and 6.5% sodium chloride (3rd Choice).