Cultivation and Laboratory Maintenance of Chlamydia trachomatis

Chlamydia species are obligate intracellular bacteria that require growth inside mammalian cells for propagation and survival. As a result, Chlamydia cannot be grown on conventional bacteriological medium. This property makes Chlamydia difficult organisms to grow and maintain in the laboratory. Up until 1965, passage in the yolk sac of the embryonated hen egg was the only way to isolate and propagate the organism. Since then, a tissue culture system has been available that allows easier laboratory culture of the Chlamydia species. However, with the exception of the LGV serovars, most C. trachomatis strains do not readily infect tissue culture cells. Chemical or mechanical assistance is used to increase their infectivity. Today, large numbers of infectious organisms can be purified through Renografin density gradient centrifugation of infected cell lysates. The ability to propagate C. trachomatis in the laboratory has greatly increased the understanding of the pathogenesis of C. trachomatis organisms.