Aims: To assess the value of detecting Toxoplasma gondii in human blood samples using the polymerase chain reaction (PCR). (7 Clin Pathol 1992;45:910-913)

Four out of 6 goats from a small British goat herd gave birth to weak or stillborn kids. All were seropositive for Toxoplasma gondii. The parasite was isolated from the tissues of one kid and the milk of one goat. Concurrently, one of the goatowner's sons developed a mononucleosis-like illness with serological evidence of current toxoplasma infection. Investigation of the family showed past infection in the other son, but both parents were seronegative. The source of infection for both boys appeared to be the consumption of unpasteurized goat's milk.

The aim of this study was to identify a sustainable cell line and culture method that could continuously provide a sufficient quantity of Toxoplasma gondii tachyzoites to serve the needs of a general hospital laboratory. Three continuous cell lines (HeLa, LLC and Vero) and three cell-culture methods (culture in conventional flasks, culture in membrane-based flasks and an automated culture system) were investigated. In multiplicity-of-infection and time-course experiments, HeLa was the cell line of choice. Harvests from HeLa cells had significantly higher tachyzoite yields than those from LLC cells (P<0.00005) or Vero cells (P<0.05). Membrane-based flasks gave higher yields (6.15x10(6) tachyzoites/ml) than conventional flasks (1-2x10(6) tachyzoites/ml) initially, but these were not sustained. The automated cell-culture system was unsuitable for parasite culture. Continuous passage in 25 cm2 flasks was successful, yielding 1x10(6) tachyzoites/ml; viability exceeded 90% after 96-120 h of infection throughout 38 passes, during which time the viability improved and the time to harvest became more consistent. Toxoplasma gondii grown in continuous culture in HeLa cells can provide a regular supply of viable tachyzoites. Demonstration that HeLa-derived tachyzoites could be used for the dye test confirms the potential of this in vitro system for use in general hospital laboratories.

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