Oesophageal thrush. Endoscope view of white patches of the fungus Candida albicans and inflammation (oesophagitis) in the oesophagus of a patient with thrush (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 compromised, the fungus may multiply excessively. The infection can be treated with antifungal drugs.