f The Use of the Serum Opacity Reaction in the Typing of Group-A Streptococci
- Authors: W. R. Maxted, Jean P. Widdowson, Cherry A. M. Fraser, Lyn C. Ball, D. C. J. Bassett
- J. Med. Microbiol., February 1973 6: 83-90, doi: 10.1099/00222615-6-1-83
- Subject: Articles
- Published Online:
A large collection of group-A streptococci was examined for the production of opacity in horse serum and for the presence of M and T antigens. Opacity production is a constant character of certain M types and is consistently absent from the rest. Testing for opacity production is a valuable addition to the serological typing procedure especially if it is carried out first. It has proved useful in (1) reducing the number of tests with M antisera that have to be set up and (2) drawing attention to errors in M typing due to the presence of cross-reacting precipitins in typing sera.
The serological specificity of the opacity factor corresponds to that of the M antigen. Inhibition of opacity production therefore provides a useful alternative method of typing strains that form the opacity factor. M antisera for opacity-producing serotypes are often of poor quality and difficult to prepare. In these circumstances, the opacity inhibition test has proved useful for preliminary identification of new M types of streptococci.
© 1973 the Pathological Sociecty of Greatb Ritain and Ireland | Published by the Microbiology Society
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