Toxoplasma gondii: Prolonged in-vitro maintenance of virulent tachyzoites in fluid media at low temperatures

Abstract

Background: Prolonged maintenance of infective Toxoplasma gondii tachyzoites (T.g.T.) is an important subject for research purposes. This study aimed to evaluate four serum free fluid media for prolonged in vitro maintenance of T.g.T.

Methods: The four fluid media Phosphate buffered saline (PBS) pH 7.2 and Roswell Park Memorial Institute (RPMI-1640) with or without 3% fetal bovine serum (FBS) were evaluated for maintenance of virulent T.g.T. The four media were tested after incubation at three different temperature degrees in the darkness.

Results: Prolonged maintenance period for infective T.g.T. was recorded especially in the absence of FBS supplement. RPMI without FBS was able to maintain infective T.g.T. for 16 days post incubation (dpi) at refrigerator temperature. This period decreased to 10 dpi and 6 dpi after incubation in the same media at 18–22 ^oC and 37 ^oC, respectively. Cultivation of T.g.T. in RPMI supplemented with 3% FBS and in PBS proved to maintain infective T.g.T. for 14 dpi at refrigerator temperature, and for 9 and 5 dpi when the two media were incubated at 18–22 ^oC and 37 ^oC, respectively. Shorter periods for keeping the T.g.T. infectivity were recorded using PBS supplemented with 3% FBS under all tested temperature conditions.

Conclusion: This method allows economic long-lasting maintenance of tachyzoites for 16th dpi in RBMI that can be reactivated by reinoculation in mice.

Keywords:  Toxoplasma gondii, Tachyzoites, Fluid media, Temperature