Oesophageal thrush. Endoscope view of white patches of the fungus Candida albicans in the oesophagus of a patient with thrush (or monoliasis or candidiasis). The fungus is normally present in the mouth, but is kept under control by bacteria which also live there. If a course of antibiotics kills the bacteria, or the patient's immune system is suppressed in any way, the fungus may multiply excessively. These white patches tend to be sore. The infection can be treated with antifungal drugs.