Yeast in a faecal culture. Scanning electron micrograph (SEM) of bacteria and yeast cultured from a sample of human faeces. Although yeast are normal bowel flora and recovery of low numbers in stool cultures is common, some hospitalized patients exhibit large numbers of yeast in stools, Environmental changes in the body, certain health issues, and the use of antibiotics can encourage the growth of Candida. If there is an overgrowth of Candida, it can cause an infection called candidiasis. Magnification: x3000 when printed at 10 centimetres wide.