Probiotics are defined as "live micro-organisms that confer a health benefit on the host when administered in adequate amounts." The major source of probiotics for humans is dairy-based foods containing intestinal species of Lactobacillus or Bifidobacterium. The most common type used is Lactobacillus acidophilus (also known as one of the "friendly bacteria"), a species of Gram-positive, rod-shaped bacteria often found in the intestinal tract of humans and animals, the human mouth and vagina. It is an anaerobic organism that produces lactic acid which reduces the pH. This may have an inhibitory effect on other organisms, especially candida. The yeast Saccharomyces cerevisiae and some Escherichia coli and Bacillus species are also used as probiotics.
This is a companion discussion topic for the original article at https://patient.info/doctor/drug-therapy/probiotics-and-prebiotics