Haemagglutination of twitching Streptococcus sanguis.

Among 86, mostly twitching, polarly fimbriated strains of Streptococcus sanguis, 55 agglutinated guinea pig erythrocytes (GPE) after cultivation in Todd-Hewitt broth (TH), and 21 strains agglutinated GPE only after growth in TH with 10% horse serum (THS). Two of the positive strains were non-twitching and unfimbriated. Ten strains failed to haemagglutinate. Among 5 twitching strains belonging to the 10043 group, 3 agglutinated GPE after growth in TH and 2 only after growth in THS. Among 35 non-twitching strains of alpha-haemolytic streptococci, only 6 agglutinated GPE after growth in TH, and among 8 negative strains which were tested after growth in THS, only 1 agglutinated GPE. Tests using 6 different kinds of erythrocytes (guinea pig, rabbit, sheep, horse, chicken, human) revealed that differences between these were slight only. The results do not indicate that there is an absolute association between twitching and haemagglutination in S. sanguis. The haemagglutination of S. sanguis was not mannose-sensitive.