Chlamydiae

Chlamydiae is a phylum of the bacteria kingdom. Development of such bacteria takes place completely within a cellular vacuole; they are hence termed intracellular bacteria.

There are four main species in this phylum: Chlamydia psittaci, Chlamydia pecorum, Chlamydia trachomatis, and Chlamydia pneumoniae. The latter two are human relates species: C. trachomatis is the famous sexually transmitted infection Chlamydia, and C. pneumoniae is a form of bacteria causing the disease Pneumonia.

They infect the individual in their first stage as an inactive particle called an infectious elementary body (EB), surviving extracellularly. After becoming cellularly internalised they become metabolically active reticulate bodies (RB). Further EBs are produced infecting surrounding cells.