There are a number of relationships the host can establish with the microbes we ingest. For the vast majority of microbes, they have a short-lived liaison with the human host. Either they are destroyed by the stomach acid or bile, or can not establish even a temporary residency in the gastrointestinal tract. Early in life the mucosal surfaces of the body establishes a resident, and generally stable, normal flora. These normal flora microbes, the majority of which are bacteria, have specific receptors for specific areas of the alimentary tract. If the foreign microbe can establish residency, it then may transiently or permanently become part of the normal flora. However, in order to produce disease, it must possess an additional set of virulence factors. While some of these are known, many are not. Those that are known include enzymes, such as protease, lipase, and esterase. Accordingly, VFAR may not be associated with human disease and its presence or absence has no public health meaning.

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