Chlamydiaceae (Ditki Notes)

• Chlamydiaceae are small, Gram-negative rods with lipo-polysaccharides in their membranes, resulting in weak endotoxin activity.
• Giemsa staining can visualize them
• Specific Major Outer Membrane Proteins (MOMPS) allow for identification of discrete serovars.
• They are "energy parasites" that rely on host cellular ATP.
• Chlamydiaceae can enter non-ciliated columnar, cuboidal, and transitional epithelial cells.
• These cells line the upper female reproductive tract, urethra, conjunctiva, and parts of the respiratory tract, marking these as sites of infection.
• It has a unique developmental cycle
• Elementary bodies are metabolically inactive infectious forms.
• Reticulate bodies are metabolically active noninfectious forms.
• This developmental cycle facilitates infection and destruction within host cells.
• An infectious elementary body is ingested by the cell and contained within a phagosome.
• Within the phagosome, the elementary body transforms into a metabolically active reticulate body.
• The reticulate body replicates via binary fission, and the daughter cells reorganize into elementary bodies.
• A phagosome containing both reticulate and elementary bodies is called an "inclusion body."
• Within a couple of days, the host cell bursts, releasing elementary bodies that can then infect new host cells.

Chlamydia trachomatis

• It is responsible for a range of infections, and are characterized by mucopurulent discharge.
• Treatment includes azithromycin, doxycycline, or erythromycin.
• Trachoma, caused by serovars A, B, and C, is a chronic infection transmitted via clothing, hands, and flies.
• Infection leads to follicular conjunctivitis, which then causes scarring that turns the eyelids and lashes inward.
• Over time, abrasions can cause corneal scarring and pannus, leading to blindness.
• Trachoma is endemic in sub-Saharan Africa, the Middle East, and South Asia, predominantly affecting children.
• Serovars D-K are the number one cause of sexually-transmitted urogenital infections in the United States.
• Many women are asymptomatic, acting as key reservoirs.
• Other women experience urethritis and/or inflammation of the reproductive tract, such as pelvic inflammatory disease and endometritis.
• Most men are symptomatic and experience urethritis.
• Co-infection with Neisseria gonorrheae is common.
• Infection can provoke reactive arthritis (Reiter syndrome) that is an autoimmune response characterized by arthritis, urethritis, conjunctivitis, and muco-cutaneous lesions.
• Vertical transmission can lead to neonatal conjunctivitis or infant pneumonia, but treatment of pregnant mothers can prevent transmission.
• Inclusion conjunctivitis is an acute follicular conjunctivitis that can become chronic with scarring with links to urogenital infections.
• Serovars L1, L2, and L3 can cause Lymphogranuloma venereum
• This sexually transmitted infection is endemic in tropical and subtropical areas, with sporadic outbreaks elsewhere.
• The early stage involves a localized lesion at the site of infection, usually the genitals or rectum.
• The lesion is painless and heals spontaneously.
• As infection moves to the lymph nodes, buboes form, typically in the inguinal or femoral regions.
• Buboes can progress to fistulas, leading to drainage/rupture and genital elephantitis, and proctitis can occur
• Proctitis affects some patients with inflammation of the anus and the lining of the rectum can cause gastrointestinal discomfort and/ or gastroenteritis.
• Systemic symptoms of lymphogranuloma venereum include fever, chills, headache, and muscle and joint pains.

Chlamydophila pneumoniae

• This can cause mild to severe respiratory infections.
• Atypical pneumonia may require hospitalization.
• Macrolide administration is usually effective.

Chlamydophila psittaci

• It is associated with birds, and thus causes Parrot fever.
• Infections can range from asymptomatic to severe, involving pulmonary, hepatic, splenic, and other organs.
• Though rare, infection can lead to organ necrosis and hemorrhage, as well as airway obstruction.
• Treatment includes doxycycline or macrolides.