ABSTRACT
Chlamydia trachomatis causes trachoma, the most common infectious cause of blindness worldwide (98). It is one of nine species that comprise the family Chlamydiaceae, three of which cause disease in humans: C. trachomatis, C. psittaci, and C. pneumoniae. There has been a move to reclassify Chlamydiaceae. However, this has not been widely accepted, so the above nomenclature will be used here (42,84). Chlamydiae are obligate intracellular bacteria, which infect many species of mammals and birds causing diverse disease. C. trachomatis causes ocular, genital, and systemic infections that affect millions of people. As C. trachomatis is responsible for most ocular disease in humans it will be the principal focus of this chapter. C. pneumoniae is associated with acute respiratory infection and is implicated in a number of chronic conditions including ischemic heart disease. C. psittaci causes a variety of infections in animals, where it is responsible for major economic losses, and occasionally it may be transmitted to humans causing atypical pneumonia.
