Objectives. Chlamydia has to replicate in cytoplasmic vacuoles of eukaryotic cells. To understand how chlamydia interacts with host cells during cell division, we examined the effect of chlamydial infection on host cell cycle.

Methods. An immunofluorescence microscopic approach was used.

Results. Although the number of cells was significantly reduced in chlamydia-infected cultures, multiple nuclei were detected in the infected cells, indicating that chlamydia inhibited host cell growth by selectively blocking cytokinesis while allowing mitosis to proceed. The chlamydial inhibition of host cell cytokinesis was confirmed with various strains of Chlamydia trachomatis and in several types of host cells. Furthermore, the chlamydial inhibitory effect was found to depend on chlamydial protein synthesis.

Discussions. These observations suggest that chlamydia may have evolved specific mechanisms for actively blocking host cell cytokinesis.