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The flora in gastrointestinal Tract of human or animals depend on food eating (fiber content) as prebiotic compounds .

This compound helping the microbial flora growth. 

campylobacteriosis is caused by either C. jejuni or C, coli and sometimes others such as C.upsalensis. In intestine there is a balance between natural probitics and pathogenic bacteria. If the balance is continued, no infection can occur. If the natural probiotics such as Lactobacilus reuteri are higher than pathogens, no infection can occur due to the produce metabolites such as lactic acid,diacetyl,carbon dioxide and bacteriocins. Due to many reasons C,jejuni or coli can be colonized in onto gut tissues ,where conditions are anaerobic and fluids or electrolytes are available and through out certain virulent factors can fix themselfes,leading to campylobacteriosis and many consequences giving intestinal ulcer