Lancefield classification based on
Carbohydrate antigen An impoant method of distinguishing between streptococci is the serological classification pioneered by American bacteriolist Rebecca lancefield who detected different versions of the major cell wall polysaccharide among the streptococci. These carbohydrates are found on the cell wall and called C carbohydrate This polysaccharide can be extracted from the streptococci with hot hydrochloric acid and the different forms can be distinguished by precipitation with specific antibodies raised in rabbits. The polysaccharide is referred to as the group polysaccharide and is identified as number of different groups labelled by capital letters. Initially the lancefield classification was limited only to pyogenes streptococci, subsequently serological grouping has been applied also to viridans streptococci and to enterococci and the number of serological groups has been extended to a total of 21 (A-H) and (k-w). Historically the lancefield antigens have been used as a major way of differentiating the many streptococci. However there are so many different streptococci that we now rely less on the lancefield antigens and more on a combination of tests such as the patterns of hernolysis, biochemical reactions, growth characteristics and genetic studies along with lancefield antigens.
M protein
Carbohydrate antigen
Cell wall peptidoglycan
T protein