Definition of probiotics and prebzotics?

An early definition of probiotics is 'organisms and substances which contribute to intestinal microbial balance'. Later the word 'substances' was removed since these could include antibiotics and microbial stimulants that are categorized as prebiotics. The revised definition is a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance. It has been suggested that the definition should be expanded to include other areas of the body e.g. skin, vagina and respiratory tract. Thus, the beneficial effect of probiotics can be mediated through the gut microflora by ingesting viable micsoorganisms. According to the definition, probiotics include not only preparations but also traditional yoghurts and other fermented foods. Prebiotics, on the other hand, are non-digestible, food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon.