To determine whether vitreous fluid Gram stains can successfully predict and indicate the

nature of intraocular bacterial infection while awaiting culture results, a retrospective study

of Gram stain and culture results on 12 endophthalmitis cases over the last two years was

conducted. Out of ten culture-positive vitreous fluids, seven demonstrated bacteria on direct

Gram stain and three had negative Gram stain results. Vitreous fluid artifacts resembling

bacteria were seen in two other Gram stains and are described. When organisms are present

in the vitreous fluid, they are frequently visible on a Gram-stained smear. The microbiologist

must be able to differentiate the Gram stain appearance of normal vitreous fluid, probable

artifacts, and infected vitreous fluid. Experience and diligence of the microbiologist are

essential to correctly evaluate the vitreous fluid Gram stains.