Chlamydial infections

Chlamydiae are pathogenic bacteria that likely evolved from host-independent, Gram-negative ancestors. Chlamydiae depend on a eukaryotic host cell for their replication which takes place in an inclusion inside the host cell, and for their dispersal, cell lysis, or extrusion subsequently occurs. Although the phylum Chlamydiae (order Chlamydiales) was originally thought to only contain one family, the Chlamydiaceae, a total of nine families are now recognized. The genus Chlamydia remains the most widely studied. The species Chlamydia trachomatis was proposed some decades ago on the basis of 16S rRNA and 23S rRNA sequences, to belong to the genus Chlamydia together with C. muridarum and C. suis. This chapter primarily focuses on the species C. trachomatis, which causes disease of ocular trachoma (serovars A–C), oculo-anogenital tract infection (serovars D–K) and lymphogranuloma venereum (serovars L1–L3). However, infections caused by C. pneumoniae and C. psittaci are also discussed.