Chalmydiae: Introduction, Morphology,Life Cycle,Pathogenecity, Lab Diagnosis and Treatment

Chalmydiae are non - motile, gram- negative obligate intracellular bacteria. They contains both RNA and DNA. They multiply within the cytoplasm of host cells, which form characteristic intracellular inclusion bodies. They can be seen with light microscope after staining with Giemsa stain better with Castaneda, Machiavello or Giminez  stains. They contain better with Castaneda, Machiavello or Giminez stains. They contain glycogen matrix. They cal also be demonstrated yb Immunofluorescence tets. The cell wall structure of Chalmydiae is close to Gram - negative bacteria. They are susceptible to Tetracycline. They have restricted metabolic activities. None of these metabolic reaction can synthesize the energy . Therefore , they have been considered as energy parasite that they use the ATP produced by the host cells for their own requirements.

Introduction of Chlamydiae

Chlamydiae are non – motile, gram-negative obligate intracellular bacteria. They contain both RNA and DNA. They multiply within the cytoplasm of host cells, which form characteristic intracellular inclusion bodies. They can be seen with a light microscope after staining with Giemsa stain better with Castaneda, Machiavelli, or Gimenez stain. They contain better with Castaneda, Machiavello or Gimenez stain. They contain a glycogen matrix. They can also be demonstrated by Immunofluorescence tests. The cell wall structure of Chlamydiae is close to Gram-negative bacteria. They are susceptible to tetracycline. They have restricted metabolic activities. None of these metabolic reactions can synthesize the energy. Therefore, they have been considered as energy parasites that use the ATP produced by the host cells for their own requirements.

Scientific classification of Chlamydia

Domain: Bacteria

Phylum: Chlamydiae

Class: Chlamydiae

Order: Chlamydiales

Family: Chlamydiaceae

Genus: Chlamydia

Species: C. trachomatis

Binomial name: Chlamydia trachomatis

Morphology of Chlamydiae

Chlamydiae occur in two forms:

  • Elementary bodies: These bodies are spherical particles, 200-300 nm in diameter with an electron-dense nucleoid. This is the extracellular infectious particle. On entry into the suitable host, it enlarges to form the reticulated body.
  • Reticulate bodies: These bodies are 500 – 1000 nm in size. It multiplies by binary fission to produce a large number of elementary bodies.

Life cycle of Chlamydia trichomatis

Chlamydiae are ingested by susceptible host cells by the mechanism of receptor-mediated endocytosis. After attachment at specific sites on the surface of the cell wall, the elementary bodies enter the cells and convert them into reticulin bodies ( Initial bodies). The chlamydiae prevent the phagolysosomal fusion. After approximately 8 hours, the initial bodies begin dividing by binary fission. Approximately 18 – 24 hours after infection, the initial bodies become elementary bodies. The initial bodies are then released and start another cycle of infection.

  • Elementary bodies coming in contact with its receptor on the host cell
  • Elementary body in process of internalization into the cell
  • Conversion of the elementary body into reticulate body.
  • Multiplication of reticulate bodies
  • Conversion of reticulate bodies into elementary bodies.
  • Elementary bodies are coming out after cell lysis.

Antigenic structure of Chlamydiae

Chlamydiae contain group (genus) specific, which is lipopolysaccharide (LPS) with a ketodexyoctonic acid antigen as the reactive moiety. It may be analogous to the LPS of certain Gram-negative bacteria. Species-specific and type antigens: Which is a major outer membrane protein. The 15 serovars of Chlamydiae trachomatis have been recognized.

Risk Factors of Chlamydia

  1. Adolescence
  2. New or multiple sex partners
  3. History of sexually transmitted infection (STD) infection
  4. Presence of another STD
  5. Oral contraceptive user
  6. Lack of barrier contraception

Transmission of Chlamydia

  • Transmission is sexual or vertical
  • Highly transmissible
  • Incubation period 7-21 days
  • Significant asymptomatic reservoir exists in the population
  • Re-infection is common
  • Perinatal transmission results in neonatal conjunctivitis in 30-50% of exposed babies

Pathogenecity of Chlamydiae

Classification based on the disease they cause

  • Chlamydia psittaci : Causative agents of Psittacosis and Ornithosis.
  • Chlamydia trachomatis : There 3 biovars.
  • Trachoma and inclusion conjunctivitis.
  • Lympho Granuloma  Venerum (LGV)
  • MoPn : Causative agent of mouse pneumonitis

Chlanydia trachomatis : It has 14 serovars: A-K

Serovars A, B, Ba, C cause classic trachoma.

Serovars D, E, F, G, H, I, J, K cause inclusion conjunctivitis, non-gonococcal urethritis, cervicitis, salpingitis, epididymitis

LGV has 3 serovars: L1, L2, L3

Chlamydia pneumoniae, previously known as TWAR strain causes acute respiratory tract infections such as pneumonia, bronchopneumonia.

Symptoms of Chlamydia

Chlamydia is a STI caused by a bacteria called Chlamydia trachomatis. Usually, it doesn’t cause any symptoms and can be easily treated with antibiotics. However, if it isn’t treated early it can spread to other parts of your body and lead to long-term health problems. In women, the infection can result in pelvic inflammatory disease (PID), which can damage the ovaries, uterus, and fallopian tubes and lead to infertility. The infection can also result in chronic pelvic pain. In men, a chlamydia infection can lead to conditions such as prostatitis, an inflammation of the prostate gland; or epididymitis, an inflammation of the coiled tube (the epididymis) internally.

In women, symptoms include:

  • Vaginal discharge
  • Burning or pain while urinating
  • Lower abdominal pain
  • Nausea
  • Fever
  • Pain during intercourse
  • Bleeding between periods

In men, symptoms include:

  • Penis discharge
  • Burning or pain while urinating
  • Burning or itching in the opening of the penis
  • Testicular pain
  • Swelling of the testicles (although this is uncommon)

Laboratory diagnosis of Chlamydiae

Sample collection:

For cytology: Vigorous swabbing or scraping of Urethra, cervix, vagina, conjunctiva

Impression smear of involved tissues

Nasopharyngeal swab or nasopharyngeal aspirates for Chlamydia pneumoniae

Note: Infected cells must be included. Purulent discharged is not satisfactory.


Chlamydia cannot be cultured in-vitro medium in the laboratory. Therefore, either tissue culture or egg inoculation is most for its culture.

  • Cell lines
  • Monkey kidney cell lines
  • HeLa cell lines
  • McCoy cell lines
  • Egg inoculation
  • Yolk sac inoculation of fertile hen’s egg.
  • Animal inoculation: seems to have less value
  • The animal model for Chlamydiae culture is mice.
  • Culture is historically the “gold standard”.
  • Variable sensitivity (50%-80%)
  • High specificity
  • Use in legal investigations
  • Not suitable for widespread screening Diagnosis


  • Complement Fixation Test (CFT)
  • Note: Antibody titer 1:64 or more is significant
  • Skin test: It does not have much value and how has been discarded  Frei test: An intradermal test described by Frei in 1923.

Treatment of Chlamydiae

Tetracycline and erythromycin are the drugs of choice. Penicillin is not effective.


Trachoma occurs worldwide and is prevalent in Africa and Asia. Chlamydia trachomatis usually is inoculated into the eye by contaminated fingers or fomites or, in neonates, by passage through an infected birth canal. Genital infections are spread venereally, and respiratory infections are usually by inhalation. Psittacosis is acquired from infected birds.

Prevention and Control of Chlymydiae


The only safe way to prevent chlamydia is to abstain from sexual contact with others. Following ways to reduce risk include:

  1. Using condoms during every sexual enter course.
  2. Reducing the number of sex partners
  3. Undergoing regular screenings and is important for reasons-
  • Screening can reduce the incidence of PID by more than 50%.
  • Most infections are asymptomatic.
  • Screening decreases the prevalence of infection in the population and reduces the transmission of disease.


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