Ans. is 'd' i.e., Propionibacterium acnes * Organisms depends upon the type of endophthalmitis A) Exogenous endophthalmitis 1) Post - operative i) Acute post - operative (within 1-7 days after surgery) :- S. epidermidis, S.aureus, Streptococcus, Gram negative bacilli. ii) Delayed onset (a week to months after surgery);- Fungi (Most common), Propionibacterium acne (2nd most common). 2) PosttraumaticBacillus, S.epidermidis, fungi, streptococcus spp. B) Endogenous endophthalmitis .--Bacillus cereus (especially in i.v. drug abusers), S. aureus, streptococci, H.influenzae, meningococci, Mucor & Candida. D Propionibacterium acnes. (Ref 2 . Retina: color atlas and synopsis of clinical ophthalmology By Allen C. Ho pg. 115) Propionibacterium acnes LATE ONSET ENDOPHTHALMITIS Definition: * Intraocular infection involving the vitreous cavity after previous ocular surgery (more than 6 weeks). Epidemiology and etiolgogy: * The usual causative organism is Propionibacterium acnes, but infection may also be caused by Stahylococcus epidermidis or fungi (Candida). Presentation: * May occur up to 2 or more yrs after surgery. History: * Patients have variable decreased vision with photophobia, and gradual onset of symptoms. Infection may be painless. Important clinical signs: * Vitritis, with or without hypopyon, more than 4 - 6 weeks after surgery; anterior chamber keratic precipitates; white plaque on intraocular lens or posterior lens capsule. * Associated conjunctival injection may be present. D/D: * Postoperative inflammation. * Rebound inflammation after discontinuing steroids. Diagnostic evaluation: * Clinical exam and USG showing vitritis and variable sclero-choroidal thickening. Prognosis and management: * Intravitreal tap and injection of vancomycin (or clindamycin, 1 mg/0.1 mL) may not be curative. Patients may require vitrectomy with capsulotomy or, sometimes, explantation of the IOL and entire lens capsule. Host flora is usually responsible for early cases of endophthalmitis and Staphylococcus epidermitis is the most common organism. Gram-negative organisms such as H. influenzae are isolated most frequently from late onset endophthalmitis