The disruption in the normal flora of the gut is largely due to abuse of antibiotics which not only have harmful effect in man but in animals as well.
Campylobacter is an important player here; causes intestinal infections as it normally inhabits the gut of warm blooded animals such as poultry and cattle and are usually detected in products derived from them.
Campylobacter are the major causes of food borne illness in homes,usually characterized by abdominal pain, vomiting and diarrhoea.