Which organism is commonly associated with blepharitis?

• A. Staphylococcus aureus
• B. Staphylococcus epidermidis
• C. Streptococcus pneumoniae
• D. Pseudomonas aeruginosa

Answer: (A)

Blepharitis is inflammation of the eyelid margin, often with crusting and irritation. The organism most commonly linked to this condition is Staphylococcus aureus. This bacterium is a highly virulent skin pathogen that frequently colonizes the eyelid margins and hair follicles, producing crusts and erythema characteristic of anterior blepharitis. Its prominence as a cause in clinical practice and exams comes from its ability to invade and persist on the lid margin, making it the classic association for blepharitis.

Staphylococcus epidermidis is also a normal skin inhabitant and can contribute to lid disease, especially in chronic or biofilm-associated cases, but it’s generally considered a less prominent, secondary player compared with Staphylococcus aureus. The remaining organisms listed are more commonly linked to other ocular infections—Streptococcus pneumoniae with conjunctivitis and sinus-related issues, and Pseudomonas aeruginosa with contact lens–related keratitis—so they’re not the typical culprits for blepharitis.