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Lancefield Grouping for Streptococcus Showing Agglutination (Labeled view) Send Print

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Created: Tuesday, 01 November 2011
Last update: Tuesday, 01 November 2011
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Lancefield Grouping for Streptococcus Showing Agglutination (Labeled view)

Lancefield grouping for Streptococcus showing agglutination.  Agglutination is occurring in only one of the six combinations of antigen-antibody used in this test. An unknown species of Streptococcus was subjected to analysis with the Lancefield grouping test, a commercially available latex agglutination immunological assay that detects carbohydrate in the cell wall of streptococci.  A standard amount of enzyme-extracted Streptococcus was applied to each of the six rings on the plastic card. A different solution of latex beads coated with a specific Lancefield group antibody was then put into each of the six wells, where presumably only one antibody would recognize the carbohydrate antigen of the unknown Streptococcus. Agglutination occurs when the latex beads coated with antibody specifically bind to the antigen in the ring and crosslinks of multiple latex beads result. Visible agglutination or clumping of the latex beads only occurred in well 4, which corresponds to Lancefield group D and thus identifies the unknown species as one of the group D Streptococcus.  Agglutination tests are widely used for identifying many different pathogens and are quick, sensitive, and specific. (Labeled view) (Janelle Hare, Morehead State University, Morehead, KY)