EVALUATION OF CULTURE CONDITIONS USED FOR ISOLATION OF CHLAMYDIA-PNEUMONIAE

As only a few viable strains of the frequent respiratory pathogen Chla mydia pneumoniae have been isolated worldwide, improvement and standar dization of isolation procedures is mandatory for adequate diagnosis a nd recovery of strains for further investigation. Growth rates of eigh t C pneumoniae strains were assessed for five host cell lines, for the growth-promoting effect of host cell cytostasis, for infection of adh erent or suspended host cells, for optimal first passage incubation ti me, and for use of multiple blind passages. Cycloheximide-treated HEp- 2 or NCI-H 292 monolayers appeared most sensitive for isolation of C p neumoniae. No significant improvement of sensitivity was achieved by e xtending first passage incubation periods from 3 to 7 days. In contras t, continuous propagation in 4 culture passages yielded on average a 7 -fold enhanced chlamydial recovery. Additional comparative isolation o f two wild-type strains showed highest inclusion counts in HEp-2 cells , but subculture was necessary for optimal sensitivity. A widely appli cable protocol using tissue culture plates for isolation of C pneumoni ae is suggested.