繼代培養法による緑色レンサ球菌群の諸性状の變化に關する研究, 特にStreptococcus sanguisの特異性について

抄録

It is well known that Streptococci belonging to the viridans group are frequently found in the upper respiratory tract of man. Their biochemical and serological characteristics are extremely complicated as previously reported by the author. It was also pointed out in the previous report that Streptococcus sanguis, a species of the viridans streptococcus group and known as one of the pathogens of subacute bacterial endocarditis, could not be regarded as a normal inhabitant of human nasopharyngeal mucosa.
To explore a possible variation of other viridans streptococci to Streptococcus sanguis, and with that to examine the adequacy of taxonomy of this bacterial group, the stability of the viridans streptococcus group was investigated in its various properties.
Four strains of Streptococcus mitts isolated from the nasopharyngeal mucosa of 4 healthy persons, and a strain of Streptococcus sanguis isolated from the blood of a patient with subacute bacterial endocarditis were cultured aerobically on horse blood agar Plates for 48 hours. Each of the strains was subcultured successively on the same agar, Streptococcus mitts down to the 100th transfer and Streptococcus sanguis to the 50th. Biochemical and serological aspects of each strain were checked at every 10th transfer. Under this condition, the biochemical qualities of Streptococcus mitts were liable to non-directed and unstable changes. Serologically the group reactions among the strains tested were changeable and unstable. These circumstances were regarded to be the cause to complicate the classification of Streptococcus viridans and to obscure the causative organism in infections associated with this bacterial group.
Contrary to these strains, Streptococcus sanguis was stable in its characteristics under successive transfers so far tested, and indicated a different nature from that of other members of the viridans streptococcus group belonging to normal inhabitants of human nasopharyngeal mucosa.