Subtopic 1: Beta-hemolytic Streptococci
Streptococci that use hemolysins to completely hemolyze red blood cells are termed beta-hemolytic. The beta-hemolytic streptococci are all pathogenic and must be carefully identified. Lancefield groups A, B, C, G, and F are all beta-hemolytic.
Streptococcus pyogenes is the most frequently encountered pathogen among the beta-hemolytic streptococci. Streptococcus pyogenes is the only member of the Lancefield's group A. It is extremely pathogenic because of its many virulence factors. The virulence factors include the M-protein, tissue-digesting enzymes, and streptolysins S and O, which attack leukocytes, kidneys, and heart muscle. Local infections caused by Streptococcus pyogenes include the skin infections impetigo and erysipelas, as well as pharyngitis ("strep throat"). Long-term sequelae of Streptococcus pyogenes infections are rheumatic fever and acute glomerulonephritis.
The group B pathogen, Streptococcus agalactiae, is a common opportunistic agent of wound, skin, and neonatal infections. Group B Streptococcus is normal flora of the GI tract, pharynx, and vaginal tract.
Streptococci from groups C, G, and F are sometimes isolated in pharyngitis and abscesses. They are oppotunistic pathogens.
View the beta-hemolytic pattern.