<u>Defensins, lysozymes, mucin, stomach acid, gut microbiota, tight junctions of gastrointenstinal epithelial cells</u> are the physical/chemical barriers to infection will the pathogen encounter en route to the intestine and once it reaches the intestine after eating lettuce contaminated with EHEC
Explanation:
The enterohemorrhagic strain of Escherichia coli (EHEC) grows in the intestines, produces the highly potent Shiga toxin. E.coli is a foodborne pathogen.
Innate immunity acts against the EHEC pathogens through physical and chemical barriers with certain non-specific responses.
Physical barriers include skin and mucous membrane. Chemical barriers include stomach acid, lysozyme, defensin.
Tight junctions are the watertight regions lining the gastrointestinal mucosal surface with tightly packed epithelial cells which prevent the flow of E. coli bacteria between the host compartments.
The mucous membranes covered with tight junctions secrete mucin and lysozyme.
Mucin blocks the pathogen’s ability to attach to the cell surfaces and thereby inhibits its invasion.
Lysozymes are mucosal enzymes which act against the pathogens trying to adhere to the gut epithelium.
Defensins are peptides that attack the cytoplasmic membrane of the pathogens and kill them
Stomach acid (HCl) reduces the pH of the gut and maintains an acidic environment, and thereby inhibits the entry of foodborne pathogens
Gut microbes are commensal organisms that aid immunity by:
- Colonization and creating competition for space and food
- Secreting toxins which can kill the pathogenic organisms
