Brain abscess in AIDS. Coloured computed tomography (CT) scan of an axial section through the brain of an AIDS patient, showing cerebral abscess. At top left is the lesion (yellow) of the abscess, with affected and discoloured brain tissue near it. At centre are dark ventricles of the brain; folds of the cerebrum are seen on the edge of the brain. An abscess is a collection of pus due to infection. In AIDS (Acquired immune deficiency syndrome), infections result from the lowered immunity of the patient. Cerebral abscess in AIDS patient's may be due to infection by bacteria or toxoplasma.