Chlamydial diseases

Abstract

Chlamydiae are unique among pathogenic bacteria in that they are completely dependent on their host species for survival. They are unable to multiply in any other environmental niche, and do not carry the minimum genetic code necessary to be self-sufficient. This absolute dependence on a specific host species is strongly reflected in the evolution of Chlamydia genomes. Chlamydiae have further evolved to occupy specific niches within their host species that manifest as tissue tropisms. These bacterial adaptations are counterbalanced by innate and adaptive host defenses. While Chlamydia research until recently has been hampered by an inability to genetically manipulate the bacteria, the wealth of pathogenic Chlamydia species, hosts, and tissue tropisms has provided a window into the complex relationship between these pathogens, their hosts, and the associated diseases. This chapter covers the spectrum of human illness caused by Chlamydiae, and incorporates experimental model data from closely related nonhuman Chlamydia species to better understand human disease. This approach is hopefully interesting and informative with the practical outcome of highlighting issues relevant to host defense and vaccine development.