Infectivity and Growth Characteristics in Tissue Cultures of Toxoplasma K Strain Isolated from a Naturally Infected Cat

The infectivity and growth characteristics of the Toxoplasma (Tp)-K strain isolated from a cat inapparently infected with Tp were studied in cultured PK-15 cells and compared with those of the Tp-RH and Tp-Beverley strains.The Tp-K strain tended to grow slightly slower than the Tp-Beverley strain in the cultured cells. It took 120hr (5days) after inoculation for the Tp-K and Tp-Beverley strains to infect all the cells. On the other hand, the Tp-RH strain showed faster growth and Tp organisms were observed in all the cells within 48hr after inoculation. The Tp-RH formed rosettes in the host cells. Both Tp-K and Tp-Beverley strains formed cysts 6days or more after inoculation, and infected cells were maintained for a long time without being destroyed or detached. The results suggest thatthe infectivity and growth characteristics of the Tp-K strain are similar to those of the Tp-Beverley strain.