A patient develops endophthalmitis 4 days after cataract surgery. Vitreous tap and intravitreal antibiotics are planned. The most common causative organism in acute post-cataract endophthalmitis and the first-line intravitreal antibiotic combination are:

• A Pseudomonas aeruginosa; intravitreal gentamicin + ceftazidime
• B Streptococcus viridans; intravitreal penicillin + gentamicin
• C Candida albicans; intravitreal amphotericin B
• D Staphylococcus epidermidis; intravitreal vancomycin + ceftazidime (or amikacin) ✓

Explanation

Staphylococcus epidermidis (coagulase-negative staphylococci) accounts for the majority (approximately 70%) of acute post-cataract endophthalmitis cases in the EVS (Endophthalmitis Vitrectomy Study). The standard intravitreal regimen is vancomycin 1 mg/0.1 mL (covers Gram-positive organisms) plus ceftazidime 2.25 mg/0.1 mL or amikacin 0.4 mg/0.1 mL (covers Gram-negatives). Candida causes delayed, chronic endophthalmitis with a different clinical presentation.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.