Serogrouping of Shigella sonnei
      Serogrouping of a Shigella sonnei isolated from a patient stool sample. Results indicate agglutination in group D 
      antisera. (Rebecca Buxton, University of Utah, Salt Lake City, UT)
                                                   American Society For Microbiology ©
      Serogrouping of a Salmonella Species
      Serogrouping of a Salmonella species isolated from a patient stool sample.  Results indicate agglutination in polyvalent and 
      group B antisera. (Rebecca Buxton, University of Utah, Salt Lake City, UT)
                                                   American Society For Microbiology ©
     Lancefield Grouping for Streptococcus Showing Agglutination
     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. 
     (Janelle Hare, Morehead State University, Morehead, KY)
                                                   American Society For Microbiology ©
       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)
                                                    American Society For Microbiology ©
       Effect of Different Ratios of Antibody and Antigen on Agglutination
       An illustration of the effect of antibody and antigen concentrations on the amount of antibody-antigen precipitate observed 
       in an agglutination reaction. Precipitation occurs when the concentrations of antibody and antigen allow the formation of 
       crosslinked networks, created when antibodies bind two or more antigen epitopes. Maximal precipitate is observed in the 
       concentration range termed "zone of equivalence." In the prozone region, the concentration of antibody exceeds the 
       concentration of antigen and little antibody-antigen precipitation will be formed. In the postzone region, the concentration 
       of antigen exceeds the concentration of antibody, again, limiting the production of antibody-antigen precipitate. (D. Sue Katz, 
       Rogers State University, Claremore, OK)
                                                   American Society For Microbiology ©