Most probiotics taxonomically belong to two genera, Bifidobacteria and Lactobacilli 3. However, the following may also be added in probiotics supplements: • species of Lactococcus, Streptococcus, and Enterococcus • some non-pathogenic strains of Escherichia coli (E. coli Nissle 1917) • yeast strains (Saccharomyces boulardii)