LONG CHAIN FORMATION BY STRAINS OF GROUP A STREPTOCOCCI IN THE PRESENCE OF HOMOLOGOUS ANTISERUM: A TYPE-SPECIFIC REACTION

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Abstract
Strains of group A streptococci, types 30 and 12, grow in extremely long chains in liquid media to which homologous antiserum is added. Addition of antisera to heterologous types failed to produce long chain growth. The long chain effect was destroyed by absorption of the antiserum with organisms of homologous type but was unaffected by absorption with heterologous types. The reaction was independent of complement or other heat labile factors in serum. Addition of trypsin to the culture to remove M protein from cells prevented long chain formation. The long chain effect depended upon the constant presence of antibody in the media. In its absence, the organisms promptly reverted to short chain growth. The phenomenon appears generally applicable to those strains rich in M protein with only an occasional such strain not responding as described. The applicability of this phenomenon in detecting type-specific antibody using indicator strains of a variety of streptococcal types is discussed.