Question

A 5-day-old newborn presents with mild conjunctivitis and cough. The baby subsequently develops interstitial pneumonia. Gram stain of conjunctival discharge shows no organisms. What is the most likely etiological agent?

• A. Neisseria gonorrhoeae
• B. Streptococcus pneumoniae
• C. Chlamydia trachomatis
• D. Staphylococcus aureus

Hint:

Ophthalmia neonatorum timeline: Chemical ($<24\text{ hours}$), Gonococcal ($2$--$5\text{ days}$, copious pus, Gram-negative diplococci), Chlamydial ($5$--$14\text{ days}$, staccato cough, interstitial pneumonia, intracellular inclusions).

Answer 1

The Correct Option is C

Concept:
Chlamydia trachomatis (serovars D--K) is a major cause of neonatal conjunctivitis (ophthalmia neonatorum) and afebrile interstitial pneumonitis in early infancy.
Infection is acquired vertically during passage through an infected maternal birth canal during vaginal delivery.
Explanation:
• Neonatal chlamydial conjunctivitis typically presents between 5 and 14 days of life with watery to mucopurulent discharge, chemosis, and pseudomembrane formation.

• Chlamydia trachomatis is an obligate intracellular bacterium and therefore does not show organisms on standard Gram stain, but diagnostic Giemsa staining reveals characteristic basophilic intracytoplasmic inclusion bodies.

• Approximately 10--20% of infants born to infected mothers develop chlamydial pneumonia, typically presenting at 2 to 12 weeks of age with a classic "staccato" cough, tachypnea, lack of fever, and bilateral diffuse interstitial/hyperinflation patterns on chest radiography.

• Peripheral eosinophilia ($>400\text{ cells}/\mu\text{L}$) and elevated serum immunoglobulins (IgM and IgG) are characteristically observed.

• Neisseria gonorrhoeae presents earlier (days 2--5) with hyperacute, copious, purulent eye discharge and gram-negative intracellular diplococci on Gram stain, but does not cause interstitial pneumonia.
Final Answer:
The clinical course of neonatal conjunctivitis evolving into interstitial pneumonia with negative Gram staining is classic for Chlamydia trachomatis infection.