Chlamydiaceae

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Small, Gram-negative rods.

Visualized with Giemsa staining.

Lipo-polysaccharides in their membranes.
– Weak endotoxin activity.

Specific Major Outer Membrane Proteins (MOMPS) that allow us to identify discrete serovars.

They are "energy parasites"
– They rely on host cellular ATP.

Tropism:
– Chlamydiaceae can enter non-ciliated columnar, cuboidal, and transitional epithelial cells, which line the upper female reproductive tract, the urethra, the conjunctiva, and parts of the respiratory tract.
Thus, these are the sites of infection.

Unique developmental cycle:
– Differentiate from elementary bodies, which are metabolically inactive infectious forms, to reticulate bodies, which are metabolically active noninfectious forms.

We show how this development 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 to become a metabolically active reticulate body.

The reticulate body replicates via binary fission; the daughter cells reorganize into elementary bodies.

The phagosome containing both reticulate and elementary bodies is called an "inclusion body."

Within a couple of days, the host cell bursts, which releases elementary bodies that can then go on to infect new host cells.

Chlamydia trachomatis

Responsible for a range of infections.

Infections are characterized by mucopurulent discharge.

Treat with azithromycin, doxycycline, or erythromycin.

Trachoma is a chronic infection caused by Serovars A, B, and C.
Transmitted via clothing, hands, and flies that move from person-person.

Infection leads to follicular conjunctivitis; scarring turns the eyelids and lashes inward.

Over time, the resulting abrasions can cause corneal scarring and pannus, leading to blindness.

Trachoma is endemic in areas of sub-Saharan Africa, the Middle East, and South Asia.
Children are predominantly affected.

Urogenital Infections are caused by Serovars D-K.
The top cause of sexually-transmitted urogenital infections in the United States.

Many women are asymptomatic, and, therefore, are key reservoirs; other women experience urethritis and/or inflammation of the reproductive tract (pelvic inflammatory disease, endometritis, etc.)

Most men are symptomatic and experience urethritis.

Co-infection with Neisseria gonorrheae is common.

Infection can provoke reactive arthritis, aka, Reiter syndrome, which is an autoimmune response characterized by arthritis, urethritis, conjunctivitis, and muco-cutaneous lesions.

Vertical transmission of Chlamydia trachomatis can lead to neonatal conjunctivitis or infant pneumonia; treatment of pregnant mothers can prevent transmission.

Inclusion conjunctivitis is an acute follicular conjunctivitis that can become chronic with scarring.
It is associated with urogenital infections.

Lymphogranuloma venereum is associated with Serovars L1, L2, and L3.
This sexually transmitted infection is endemic in tropical and subtropical areas; sporadic outbreaks have been reported elsewhere.

The early stage is characterized by a localized lesion at the site of infection (typically the genitals or rectum); the lesion is painless, and heals spontaneously.

However, as infection moves to the lymph nodes, buboes form; show that they typically appear in the inguinal or femoral regions. Buboes can progress to fistulas that drain and/or rupture, and genital elephantitis can develop.

Proctitis can also occur (inflammation of the anus and lining of the rectum).

Systemic symptoms of lymphogranuloma venereum include fever, chills, headache, and muscle and joint pains.

Chlamydophila pneumoniae

Causes mild to severe respiratory infections.
– Atypical pneumonia may require hospitalization.
– Macrolide administration is usually effective.

Chlamydophila psittaci

Associated with birds; thus, it is said to cause "Parrot fever."

Infections can range from asymptomatic to severe, with pulmonary, hepatic, splenic, and other organ involvement.

Though rare, infection can lead to organ necrosis and hemorrhage, as well as airway obstruction.

Treatment includes doxycycline or macrolides.

Full-Length Text

Here we will learn about pathogenic strains of Chlamydiaceae.

• Members of this family are small, Gram-negative rods.

• They can be visualized with Giemsa staining.

• As Gram-negative bacteria, they have lipo-polysaccharides in their membranes.
  – Weak endotoxin activity.

• They have specific Major Outer Membrane Proteins (MOMPS) that allow us to identify discrete serovars.

• They are "energy parasites"
  – They rely on host cellular ATP.

• Unique developmental cycle
  – Differentiate from elementary bodies, which are metabolically inactive infectious forms, to reticulate bodies, which are metabolically active noninfectious forms.

Let's show how this development cycle facilitates infection and destruction within host cells.

• First, draw a susceptible host cell.

• Show that an infectious elementary body is ingested by the cell and contained within a phagosome.

• Within the phagosome, the elementary body transforms to become a metabolically active reticulate body.

• The reticulate body replicates via binary fission; the daughter cells reorganize into elementary bodies.
  =
• Indicate that the phagosome containing both reticulate and elementary bodies is called an "inclusion body"
  – We can see examples of inclusion bodies in the histologic sample.

• Within a couple of days, the host cell bursts, which releases elementary bodies that can then go on to infect new host cells.

• Show that Chlamydiaceae can enter non-ciliated columnar, cuboidal, and transitional epithelial cells.
  – Line the upper female reproductive tract, the urethra, the conjunctiva, and parts of the respiratory tract.
  – Thus, these are the sites of infection.

With this as a background, let's consider Chlamydia trachomatis, which is responsible for a range of infections.

• Write that mucopurulent discharge characterizes these infections, many of which can be treated with azithromycin, doxycycline, or erythromycin.

• Now, indicate that trachoma is a chronic infection caused by serovars A, B, and C.

• It is transmitted via clothing, hands, and flies that move from person-person.

• Write that infection leads to follicular conjunctivitis; scarring turns the eyelids and lashes inward.

• Over time, the resulting abrasions can cause corneal scarring and pannus, leading to blindness.

• Trachoma is endemic in areas of sub-Saharan Africa, the Middle East, and South Asia; children are predominantly affected.

Next, indicate that Chlamydia trachomatis serovars D-K comprise the number one cause of sexually-transmitted urogenital infections in the United States.

• Many women are asymptomatic, and, therefore, are key reservoirs.

• Other women experience urethritis and/or inflammation of the reproductive tract (pelvic inflammatory disease, endometritis, etc.)

• Most men are symptomatic and experience urethritis.

• Be aware that co-infection with Neisseria gonorrheae is common.

• Indicate that infection can provoke reactive arthritis, aka, Reiter syndrome.
  – An autoimmune response characterized by arthritis, urethritis, conjunctivitis, and muco-cutaneous lesions.

• Write that vertical transmission of Chlamydia trachomatis can lead to neonatal conjunctivitis or infant pneumonia.
  – Treatment of pregnant mothers can prevent transmission.

Next, indicate that inclusion conjunctivitis is an acute follicular conjunctivitis that can become chronic with scarring. It is associated with urogenital infections.

Finally, indicate that Chlamydia trachomatis Serovars L1, L2, and L3 cause Lymphogranuloma venereum.

• This sexually transmitted infection is endemic in tropical and subtropical areas; sporadic outbreaks have been reported elsewhere.

• Write that the early stage is characterized by a localized lesion at the site of infection (typically the genitals or rectum); the lesion is painless, and heals spontaneously.

• However, as infection moves to the lymph nodes, buboes form; show that they typically appear in the inguinal or femoral regions.

• Write that the buboes can progress to fistulas that drain and/or rupture, and genital elephantitis can develop.

• Proctitis can also occur.
  – Show that patients experience inflammation of the anus and the lining of the rectum; some have gastrointestinal discomfort that is can be confused with gastroenteritis.

• Write that systemic symptoms of lymphogranuloma venereum include fever, chills, headache, and muscle and joint pains.

Finally, let's briefly consider two species of Chlamydophila that cause atypical pneumonia.

• First, show that Chlamydophila pneumoniae can cause mild to severe respiratory infections.
  – Atypical pneumonia may require hospitalization.
  – Macrolide administration is usually effective.

• Chlamydophila psittaci is associated with birds.
  – Thus, it is said to cause "Parrot fever."
  – Infections can range from asymptomatic to severe, with pulmonary, hepatic, splenic, and other organ involvement. –
  – Though rare, infection can lead to organ necrosis and hemorrhage, as well as airway obstruction. Treatment includes doxycycline or macrolides.

References:

• Ceovic, Romana, and Sandra Jerkovic Gulin. "Lymphogranuloma Venereum: Diagnostic and Treatment Challenges." Infection and Drug Resistance, March 2015, 39. https://doi.org/10.2147/IDR.S57540.

• Liechti, G. W., E. Kuru, E. Hall, A. Kalinda, Y. V. Brun, M. VanNieuwenhze, and A. T. Maurelli. "A New Metabolic Cell-Wall Labelling Method Reveals Peptidoglycan in Chlamydia Trachomatis." Nature 506, no. 7489 (February 2014): 507–10. https://doi.org/10.1038/nature12892.

• Nguyen, B. D., and R. H. Valdivia. "Virulence Determinants in the Obligate Intracellular Pathogen Chlamydia Trachomatis Revealed by Forward Genetic Approaches." Proceedings of the National Academy of Sciences 109, no. 4 (January 24, 2012): 1263–68. https://doi.org/10.1073/pnas.1117884109.

• Rizzo, Antonietta, Marina Di Domenico, Caterina Romano Carratelli, and Rossella Paolillo. "The Role of Chlamydia and Chlamydophila Infections in Reactive Arthritis." Internal Medicine 51, no. 1 (2012): 113–17. https://doi.org/10.2169/internalmedicine.51.6228.

• Selmi, Carlo, and M. Eric Gershwin. "Diagnosis and Classification of Reactive Arthritis." Autoimmunity Reviews 13, no. 4–5 (April 2014): 546–49. https://doi.org/10.1016/j.autrev.2014.01.005.

• Stavropoulos, P.G., E. Soura, A. Kanelleas, A. Katsambas, and C. Antoniou. "Reactive Arthritis." Journal of the European Academy of Dermatology and Venereology 29, no. 3 (March 2015): 415–24. https://doi.org/10.1111/jdv.12741.

• Stoner, Bradley P., and Stephanie E. Cohen. "Lymphogranuloma Venereum 2015: Clinical Presentation, Diagnosis, and Treatment: Table 1." Clinical Infectious Diseases 61, no. suppl 8 (December 15, 2015): S865–73. https://doi.org/10.1093/cid/civ756.

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Chlamydia Geimsa Stain CDC