Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such pathogens ? What type of  immunity do you observe in this case ?

The mucus coating of the epithelium lining of the gut helps in trapping microbes entering the body.

Saliva in the mouth contains lysozyme which kills the pathogens. hydrochloric acid in gastric juice secreted by stomach prevent microbial growth.

All these type of immunity is innate immunity.