FIG 1.

Novel plaque assay allows titration of Chlamydia species based on immunofluorescence staining. Immunofluorescence images show plaques of C. trachomatis L2 (Ctr L2), C. trachomatis A (Ctr A), C. trachomatis D (Ctr D), C. psittaci (Cps), and C. muridarum (Cmu) in a cell monolayer of HeLa 229 and McCoy cells. Cells were seeded in 48-well plates and infected with different titers. After 4 days of incubation, cells were fixed and stained for chlamydial Hsp60. Numbers indicate the dilution factor of the bacteria.