Association of a Serum Opacity Reaction with Serological Type in Streptococcus pyogenes

SUMMARY: Krumwiede (1954) reported that some group A streptococci formed a lipoproteinase which was capable of producing opalescence in horse serum. A survey of a large number of strains of group A streptococci has shown that those strains which carry an easily identifiable M antigen rarely produce the serum opalescence reaction, except for Types 2 and 9. On the other hand those types that elaborate M antigen poorly or not at all are usually good producers of the serum opacity reaction.