The most common cause of conjunctivitis in the newborn is which organism?

• A. Staphylococcus species
• B. Neisseria gonorrhoeae
• C. Chlamydia trachomatis
• D. Pseudomonas aeruginosa

Answer: (C)

Neonatal conjunctivitis is typically caused by organisms transmitted from the mother during birth, and the timing of onset helps distinguish them. Neisseria gonorrhoeae tends to cause a very abrupt, severe conjunctivitis within the first couple of days after birth, with bold purulent discharge. Pseudomonas and Staphylococcus can cause eye infections but are not the most common neonatal culprits. Chlamydia trachomatis, on the other hand, is the most common cause of newborn conjunctivitis overall and usually presents later, about 5–14 days after birth, with mucopurulent discharge and sometimes accompanying pneumonitis.

Therefore, Chlamydia trachomatis best fits as the most common cause. Management requires systemic antibiotics rather than topical therapy alone, because the infection can be disseminated and intraocular penetration with oral antibiotics helps prevent progression.