Isolation of antigenic variants from leptospiras grown in vitro and from heart blood of guinea pigs inoculated with a clonized strain of Leptospira.

A clonized culture of Leptospira interrogans serovar copenhageni strain Shibaura (Cl-Shibaura) was inoculated into guinea pigs. The heart blood of the guinea pigs, obtained at the febrile stage and inoculated onto the solid serum medium containing the homologous immune serum, produced large and small colonies. The serological examinations revealed that the large colonies were found mainly to be the antigenic variants, while the small colonies were mostly the parent. The antigenic variants accounted for 16.4% of all the colonies from the blood of the guinea pigs infected with Cl-Shibaura, and for 1.2% of all the colonies from the blood of the guniea pigs infected with Cl-Shibaura, and for 1.2% of all the ll colonies. The serological examinations revealed that the large colonies were found mainly to be the antigenic variants, while the small colonies were mostly the parent. The antigenic variants accounted for 16.4% of all the colonies from the blood of the guniea pigs infected with Cl-Shibaura, and for 1.2% of all the colonies from the culture of Cl-Shibaura in the normal serum medium. Antigenic variants were also isolated in vitro from the culture of 2 other serovars. The fact that the frequency of the antigenic variants of leptospiras was higher in vivo than in vitro is discussed.