Chlamydiaceae

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Sexually Transmitted Disease

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Pathophysiology
Types: Genus Chlamydia
Types: Genus Chlamydophila
References
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II. Pathophysiology

Chlamydiaceae is a family of Gram Negative Cocci with 2 genera
1. Chlamydia
  1. Chlamydia Trachomatis is the primary species in the Chlamydia genus
  2. Chlamydia Trachomatis is the most common Sexually Transmitted Infection (STI) worldwide
2. Chlamydophila
  1. Chlamydophila species are uncommon to rare organisms in human disease
  2. Chlamydophila psittaci (bird borne Zoonosis)
  3. Chlamydophila pneumoniae or TWAR (uncommon Atypical Pneumonia)
Chlamydiaceae are more akin to viruses than Bacteria
1. Tiny Gram Negative Cocci
  1. Chlamydia Elementary Body is only 300 nm (nearly the diameter of a large virus)
  2. Like other Bacteria, they have both DNA and RNA (while viruses have one or the other)
2. Chlamydiaceae lack a peptidoglycan layer (unlike other Gram Negatives)
  1. However, they do contain an inner and outer membrane (as with other Gram Negative Bacteria)
  2. Lack of peptidoglycan layer renders Chlamydiaceae immune to attack from Penicillins
3. Obligate intracellular Parasites
  1. Similar to viruses (as well as a few other Bacteria families including Rickettsiae)
  2. Chlamydiaceae rely exclusively on host cell energy production (via ATP-ADP Translocator)
    1. Contrast with Rickettsiae, which can also generate its own energy
  3. Chlamydiaceae can only be cultured in live media
    1. Cell culture
    2. Chick embryo Yolk Sac
Chlamydiaceae exist in 2 forms
1. Elementary Body (EB)
  1. Tiny, round infectious particle (300 nm)
  2. Strong outer membrane of disulfide cross-linked bonds
  3. Inert, non-dividing particle able to persist extracellularly between hosts
  4. Elementary body (EB) attaches to columnar epithelial cells on mucous membranes (e.g. vagina)
    1. EB enters the columnar cells via endosomes (endocytosis)
    2. EB inhibits Phagosome-Lysosome fusion on Phagocytosis
    3. Once intracellular, EB transitions to Initial Body (as below)
2. Initial Body (IB, Reticulate Body)
  1. Starts with Elementary Body (EB) entering host cells via Phagocytosis
  2. Within host cells, EB triples its size (to 1000 nm), increasing RNA synthesis
  3. EB particles then divide via binary fission within host cells, forming Initial Bodies (IBs)
  4. IBs are the active infectious agent within cells
    1. Synthesize RNA
    2. Harvest energy from host cells via ATP-ADP Translocator
    3. Reproduce via binary fission
  5. Once IBs accumulate within the host cell, they form EBs to infect other cells
    1. Some IBs transform back into EBs, to exit the host cell and infect other cells

III. Types: Genus Chlamydia

Organism
1. Chlamydia Trachomatis
Eye Diseases
1. Chlamydial Conjunctivitis (Inclusion Conjunctivitis, serotypes D to K)
2. Trachoma (Conjunctival scarring with blindness, serotypes A to C)
Genitourinary Disease
1. Lymphogranuloma venereum (serotypes L1 to 3)
2. Non-Lymphogranuloma venereum (serotypes L1 to 3)
  1. Chlamydial Urethritis
  2. Chlamydial Cervicitis
  3. Chlamydial Pelvic Inflammatory Disease (including Salpingitis)
Respiratory
1. Chlamydia Pneumonia in Newborns (serotypes A to C)

IV. Types: Genus Chlamydophila

Chlamydophila psittaci (previously Chlamydia psittaci)
1. Human Psittacosis from bird borne Zoonosis
2. Respiratory illness or typhoidal illness
Chlamydophila pneumoniae (TWAR)
1. Atypical Pneumonia

V. References

Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 110-1
Cheong (2019) Microorganisms 7(5):146 +PMID: 31137741 [PubMed]

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