Chlamydia trachomatis - Classification, Introduction, Habitat, Culture, Antigen, Typing

Classification of Chlamydia trachomatis

Domain: Bacteria

Phylum: Chlamydiota

Class: Chlamydiia

Order: Chlamydiales

Family: Chlamydiaceae

Genus: Chlamydia

Species: trachomatis

Introduction to Chlamydia trachomatis

Chlamydia trachomatis can be introduced as a gram-negative bacterium that causes chlamydia, a common sexually transmitted infection (STI). It is stained better by Giemsa, Castaneda, Machiavello, or Gimenez stains.

The Elementary body (EB) of Chlamydia trachomatis can be demonstrated in the conjunctive, urethra, and corneal smear by light microscopy. It also contains a glycogen matrix, demonstrated on staining with Lugol’s iodine.

It includes 18 serovars on basis of Major Outer Membrane Protein (MOMP). Virulence factors of Chlamydia trachomatis include:

• Major Outer Membrane Protein (MOMP)

• Lipopolysaccharide (LPS)

The bacteria multiply intracellularly. It prevents the fusion of phagolysosomes with cellular liposomes preventing intra-cellular killing by the host cells.

Habitat of Chlamydia trachomatis

Chlamydia trachomatis is a strict human pathogen. The bacteria habitats the conjunctiva, genitourinary tract, respiratory, and gastrointestinal tracts of humans.

Culture of Chlamydia trachomatis

Chlamydia trachomatis can be cultured in tissue cultures and cell lines such as HeLa-229, McCoy, BHK-21, and buffalo green monkey kidney cells are used.

The embryonated egg inoculation was done in the yolk sac of a 6-8 day-old chick embryo. The presence/growth of chlamydia is demonstrated by the presence of elementary and inclusion bodies as well as group-specific complement-fixing antigens in the yolk sac.

Animal inoculation is also done. Different strains such as L1, L2, and L3 differ in infertility.

Chlamydia trachomatis is heat-labile (killed within minutes at 56°C) but remains fully viable for several days at 4°C. They are susceptible to ethanol, ether, phenol, iodine, and formalin. Preservation can be done at -70°C or in liquid Nitrogen.

Cell wall components, antigenic structure of Chlamydia trachomatis

Chlamydia trachomatis possess 3 types of major antigens/antigenic structures/cell wall components:

1. genus-specific antigens

2. species-specific antigens

3. serotype-specific antigens

Genus-specific antigens

• the genus-specific antigens of Chlamydia trachomatis are heat-stable, complement-fixing, and genus-specific Ag with an LPS-protein complex resembling the LPS of gram-negative bacilli

• It is present in EBs and Rbs.

• This Ag can be identified by CFT.

Species-specific Ag

• the species-specific antigen of Chlamydia trachomatis is present in all strains of Chlamydia at the envelope surface

• It is species-specific

Serotype-specific Ag

• Only present in a few species of Chlamydia

• serotype-specific Ag of Chlamydia trachomatis is located in MOMPs

• useful for intraspecies typing for Chlamydia species

Typing of Chlamydia trachomatis

Chlamydia trachomatis has been subdivided/typed into biological variants or biovars. Biovars have been classified into 20 serotypes on the basis of MOMPs.

1. Trachoma biovar = 13 serotypes: causes trachoma and inclusion conjunctivitis (TRIC)

2. Lymphogranuloma venereum (LGV) = 5 serovars

3. Serovars causing mouse pneumonitis