What is the causative agent of ophthalmia neonatrum?

The causative agent of ophthalmia neonatrum is Neisseria gonorrhoeae. This condition is an inflammation of the eyes that occurs in newborns, primarily due to the transmission of the bacteria during childbirth when the infant passes through the birth canal of an infected mother. Neisseria gonorrhoeae is known for causing gonorrhea, and its presence can lead to severe ocular infections in neonates if not properly addressed with prophylactic treatments, such as the instillation of antibiotic drops immediately after birth.

The connection lies specifically in how the bacteria affect the mucous membranes, making them capable of causing conjunctivitis in newborns. The other options, while they can cause various infections, are not specifically known to be the causative agents of ophthalmia neonatrum. Streptococcus can lead to a range of infections, and while Escherichia and Haemophilus can also cause infections in the eye, they do not specifically correlate with the condition of ophthalmia neonatrum in neonates. Thus, Neisseria gonorrhoeae is the recognized and significant pathogen for this condition, making it the correct answer.