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?

(N/A) 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 $(HCl)$ in the gastric juice secreted by the stomach prevents microbial growth.
All these barriers are part of the innate immunity,specifically physiological barriers.