Which organism is the most common cause of acute bacterial conjunctivitis in adults in India?

Explanation

## Epidemiology of Acute Bacterial Conjunctivitis **Key Point:** Staphylococcus aureus is the most common cause of acute bacterial conjunctivitis in adults globally, including India, accounting for approximately 30–50% of bacterial cases. ### Common Bacterial Causes by Frequency | Organism | Frequency | Clinical Features | Geographic Variation | |----------|-----------|-------------------|----------------------| | Staphylococcus aureus | 30–50% | Purulent discharge, mild inflammation | Most common in adults worldwide | | Streptococcus pneumoniae | 5–15% | Mucopurulent discharge, may have pseudomembrane | More common in children | | Haemophilus influenzae | 10–20% | Acute onset, copious purulent discharge | More common in children <5 years | | Neisseria gonorrhoeae | <5% | Severe purulent discharge, chemosis, lid edema | Sexually transmitted; neonatal ophthalmia | **High-Yield:** In neonates (ophthalmia neonatorum), Neisseria gonorrhoeae and Chlamydia trachomatis are the leading causes. In children aged 5–15 years, Haemophilus influenzae is more prevalent. In adults, Staphylococcus aureus dominates. ### Clinical Pearl **Staphylococcus aureus** typically presents with: - Unilateral or bilateral purulent conjunctivitis - Mild to moderate lid swelling and erythema - Often associated with blepharitis or meibomianitis - Responds well to topical antibiotics (fluoroquinolones, aminoglycosides) **Tip:** Remember the age-based distribution: neonates → gonorrhea/chlamydia; children → Haemophilus; adults → Staph aureus.