Which is the most common etiologic agent of Phlyctenular conjunctivitis?

Phlyctenular conjunctivitis is a delayed hypersensitivity (Type IV cell mediated) response to endogenous microbial proteins most commonly staphylococcus proteins. Previously, tuberculous proteins was considered as the most common cause. Also know: Signs of phlyctenular conjunctivitis: Simple phlyctenular conjunctivitis: Most common variety. It is characterized by the presence of a typical pinkish white nodule surrounded by hyperemia on the bulbar conjunctiva near the limbus. Necrotizing phlyctenular conjunctivitis: Is characterised by the presence of a very large phlycten with necrosis and ulceration leading to severe pustular conjunctivitis. Miliary phlyctenular conjunctivitis: Is characterised by the presence of multiple phlyctens which may be arranged haphazardly or in the form of a ring around the limbus. Ref: Comprehensive ophthalmology By AK Khurana, 4th edn, page 77-8