Trachoma is caused by which organism and is the leading cause of preventable blindness worldwide?

• A. Chlamydia trachomatis
• B. Ophthalmia neonatorum
• C. Neisseria gonorrhoeae
• D. Streptococcus pneumoniae

Answer: (A)

Trachoma is caused by Chlamydia trachomatis, specifically the ocular serovars A to C. Repeated infections over years trigger chronic inflammation of the conjunctiva, leading to scarring of the eyelid margin and inward turning of the eyelashes (trichiasis). Those lashes rub against the cornea, causing corneal scarring and eventual blindness. This combination of transmission in crowded, low-resource settings and the potential to prevent it with antibiotics, improved hygiene, and facial cleanliness is why trachoma is the leading preventable cause of blindness worldwide. The other options are not the cause: ophthalmia neonatorum refers to neonatal conjunctivitis (often from gonorrhea or chlamydia), Neisseria gonorrhoeae causes a hyperacute conjunctivitis, and Streptococcus pneumoniae can cause conjunctivitis but does not produce the chronic scarring that leads to trachoma.