A modified isolation technique for Chlamydia psittaci in L-cells treated with cycloheximide and glucocorticoid.

Various auxiliary treatments of L-cells employed for the isolation and cultivation of C. psittaci were investigated in order to develop an improved method for the detection of the agent, in addition to the aid obtained by centrifugation and cycloheximide treatment. Glucocorticoid treatment increased the observed number of inclusions considerably through a preservative effect on host cells and enhanced an spontaneous re-infection. Besides, the hormone made the scanning of cell culture for inclusions more convenient through an altered cell morphology. This method was tested with two extreme species types that differed as regards cytopathogenicity and growth rate. The length of the cultivation period was of great importance for the diagnostic result. Especially the cytopathogenic agent-type influenced the optimal time of cell culture fixation, which was situated around 48 or 88 hours post infection (h p.i.). Owing to the cytotoxicity of field samples (milk secretion), the cell culture technique (48 h p.i.) was less sensitive compared to the conventional isolation method in embryonated eggs. However, a different sampling technique improved the result, and simultaneous use of the secondary multiplication cycle of chlamydia (88 h p.i.) makes the less cumbersome cell culture technic recommendable.