An obligate intracellular bacterium behind both the world’s leading infectious cause of blindness and its most reported bacterial STI. Explore its illustrative 3D model, human context, and sources.
PHAC describes C. trachomatis as a nonmotile, Gram-negative, obligate intracellular pathogen around 0.3 to 1 micrometre in diameter with a biphasic lifecycle: an elementary body for extracellular survival and a reticulate body for intracellular replication. Eighteen serovars are recognised — four causing trachoma, five causing lymphogranuloma venereum and the remainder causing other sexually transmitted infections — so one species name covers strikingly different diseases. WHO estimated 129 million new chlamydia infections worldwide in 2020. Separately, WHO reports trachoma as a public health problem in at least part of 29 countries, with about 1.9 million people blind or visually impaired from it.
PHAC states that genital infections may be asymptomatic, and CDC that chlamydia often has no symptoms but can cause serious health problems even without symptoms. Risk depends heavily on which serovar and which site: trachoma serovars cause repeated eye infection that scars, LGV serovars cause lymphatic disease, and genital serovars can cause pelvic inflammatory disease and infertility when untreated. A serovar-specific finding must not be generalised across the species.
Chlamydia trachomatis · One small, dense elementary body is represented. The larger intracellular reticulate body is a separate form and is not shown. This is a species-informed teaching diagram; colours, proportions, envelope spacing and internal detail are illustrative. The single-cell division graphic simplifies the different intracellular form. The model uses muted illustrative colours; stains, colony pigments and microscopy colourization are not natural cell colours. Anatomy is enlarged for phone viewing. Morphology reference: Chlamydia trachomatis · pathogen safety data sheet.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.