A 55-year old man presented with a two-day history of headache, fever and generalized weakness. He had received a cadaveric kidney transplant 5 years earlier. His medications included 5 mg oftacrolimus twice a day and 10 mg of prednisone daily. On neurologic examination, he was confused and incoherent. Cranial nerves were normal, but he had a hazy left retina. Magnetic resonance imaging of the brain with the administration of gadolinium showed multiple enhancing lesion in both cerebral hemispheres. Patient had subretinal abscess, the aspirate was stained, the findings are liekly to be -