Many different bacteria and viruses can cause conjunctivitis in the neonate. The two most feared causes are N. gonorrheae and Chlamydia acquired from the birth canal during delivery.Other agents causing Opthalmia neonatorum include Herpes simplex virus (HSV 2), Staphylococcus aureus, Streptococcus haemolyticus, Streptococcus pneumoniae.
Ophthalmia neonatorum due to gonococci (Neisseria gonorrhoeae) typically manifests in the first five days of life and is associated with marked bilateral purulent discharge and local inflammation. In contrast, conjunctivitis secondary to infection with chlamydia (Chlamydia trachomatis) produces conjunctivitis after day three of life, but may occur up to two weeks after delivery. The discharge is usually more watery in nature (mucopurulent) and less inflamed. Babies infected with chlamydia may develop pneumonitis (chest infection) at a later stage.Infants with chlamydia pneumonitis should be treated with oral erythromycin for 10–14 days.