Chlamydiales

An order of bacteria that includes several important pathogens.

Chlamydiales is an order of bacteria that are obligate intracellular pathogens. This order includes several families, with the most notable being the family Chlamydiaceae, which contains the genus Chlamydia. Members of this order are known to cause a variety of diseases in humans and animals.

Characteristics

Chlamydiales are small, gram-negative bacteria that lack peptidoglycan in their cell walls. They have a unique developmental cycle that includes two distinct forms: the elementary body (EB) and the reticulate body (RB). The EB is the infectious form that is able to survive outside of host cells, while the RB is the replicative form that multiplies within host cells.

These bacteria are obligate intracellular organisms, meaning they can only grow and reproduce inside the cells of a host organism. They are known to infect epithelial cells, macrophages, and other cell types.

Pathogenesis

Chlamydiales are responsible for a range of diseases in humans and animals. The most well-known species, Chlamydia trachomatis, is a major cause of sexually transmitted infections (STIs) and can lead to conditions such as chlamydia, trachoma, and lymphogranuloma venereum.

Other species, such as Chlamydophila pneumoniae, are associated with respiratory infections, while Chlamydophila psittaci is known to cause psittacosis, a disease transmitted from birds to humans.

Diagnosis and Treatment

Diagnosis of infections caused by Chlamydiales typically involves nucleic acid amplification tests (NAATs), which are highly sensitive and specific. Serological tests and culture methods may also be used in certain cases.

Treatment usually involves the use of antibiotics such as azithromycin or doxycycline. Due to the intracellular nature of these bacteria, antibiotics that can penetrate host cells are required.

Research and Public Health

Research on Chlamydiales is ongoing, with efforts focused on understanding their unique biology, pathogenesis, and developing effective vaccines. Public health measures aim to reduce the incidence of infections through screening, education, and treatment programs.

Also see

• Chlamydia (genus)
• Chlamydia trachomatis
• Chlamydophila pneumoniae
• Sexually transmitted infection
• Obligate intracellular parasite