Some streptococci can also be classified based on the antigenic characteristics of the C carbohydrate (a car­bohydrate found on the cell wall). These antigens are called Lancefield antigens and are given letter names. Historically, the Lancefield antigens have been used as a major way of differentiating the many streptococci. Clinically significant Lancefield groups include A, B, C, F, and G. Streptococcal group antigens are extracted from the streptococcal cell wall in a liquid form, and reacted with group specific antibodies. The grouping kits are available commercially.

Why are the groups called "Lancefield"?

Obtain a commercially prepared Enzyme Latex Test kit for the identification of Lancefield streptococcal groups A, B, C, D, F, and G. Follow instructions in the kit to perform the procedure. Use the kit to test Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus bovis.

All beta-hemolytic streptococci should be tested with A, B, C, F, and G. Gamma strep should be tested with D.

In your lab report, describe the reactions for Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus bovis. Identify which species react with which group.