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

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

• A. Moraxella catarrhalis
• B. Haemophilus influenzae
• C. Streptococcus pneumoniae
• D. Staphylococcus aureus

Answer: (D)

Staphylococcus aureus is the most common cause of acute bacterial conjunctivitis in adults because it readily colonizes the skin and eyelids and easily contaminates the conjunctival surface, making infection a frequent event. Clinically, it often presents with redness, a gritty sensation, and purulent discharge that crusts the lids, and it can be unilateral at first. Other organisms do occur, but they’re less common in adults: Moraxella species are more associated with angular conjunctivitis and chronic lid disease; Haemophilus influenzae and Streptococcus pneumoniae are more typical causes in children due to different patterns of nasopharyngeal colonization.

Staphylococcus aureus is the most common cause of acute bacterial conjunctivitis in adults because it readily colonizes the skin and eyelids and easily contaminates the conjunctival surface, making infection a frequent event. Clinically, it often presents with redness, a gritty sensation, and purulent discharge that crusts the lids, and it can be unilateral at first. Other organisms do occur, but they’re less common in adults: Moraxella species are more associated with angular conjunctivitis and chronic lid disease; Haemophilus influenzae and Streptococcus pneumoniae are more typical causes in children due to different patterns of nasopharyngeal colonization.