Which bacteria penetrates intact cornea ?
Ans. is 'a' i.e., Corynebacterium Bacterial corneal ulcer Bacterial corneal ulcer, also called suppurative keratitis, is due to organisms that produce toxin which cause tissue necrosis and pus formation in the corneal tissue. Purulent keratitis is nearly always exogenous, due to pyogenic organism. As long as the cornea is healthy, the majority of bacteria are unable to cross or adhere to the corneal epithelium. Therefore the two main predisposing factors for bacterial corneal ulcer are : - Damage to corneal epithelium Infection of the eroded area However, there are a few species that are capable of penetrating an intact epithelium : - Neisseria gonorrhoea Neisseria meningitidis Corynebacterium diphtheriae Listeria species Haemophilus agyptus Bacteria which cause corneal ulcer (Purulent keratitis) after epithelial injuries are : - Pseudomonas Pneumococcus Streptococcus epidermidis Staphylococcus aureus Morexella Enterobacterias Proteus, Klebsiella) Although there are specific presentations depending on the bacteria involved, there exists a series of symptoms and signs common to all that allow for a rapid diagnosis, and therefore early treatment of corneal ulcers. The most impoant symptoms are pain, lacrimation, foreign body sensation, conjunctival injection (red eye), photophobia and blurred vision. There is lid swelling, blepharospasm and yellow white areas of ulcer with swollen and overhanging marin may be seen.
Corynebacterium
Pneumococcus
Morexella
E. coli