Overview and Objectives
Main Topic
Subtopic 1:
Beta-hemolytic Streptococci
1.1, 1.2, 1.3
  Subtopic 1 Summary
Subtopic 2: Alpha-hemolytic streptococci
  Activity 2
  Subtopic 2 Summary
Subtopic 3: Gamma Streptococci
3.1, 3.2
  Subtopic 3 Summary
Module Summary

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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.