Abstract: Bacterial extracellular vesicles (BEVs) are nano-scale membrane-enclosed structures actively secreted by all bacteria, with a diameter ranging from 20～400 nm. They carry various bioactive molecules such as proteins, nucleic acids, and lipids, and play a key role in bacterial physiological activities and host interactions. With the integration of veterinary medicine and nanobiology, research on BEVs in the field of swine disease prevention and control is increasingly in-depth. This article systematically reviewed the biological characteristics of bacterial extracellular vesicles, compared the functional differences between BEVs derived from Gram-positive and Gram-negative bacteria, analyzed their composition and interaction mechanisms with the host, emphatically elaborated on the application practices and mechanisms of action of BEVs in postweaning diarrhea in piglets, further looked forward to their industrial application potential, aiming to provide a theoretical reference for the development of precise prevention and control technologies for postweaning diarrhea in piglets.

Key words: bacterial extracellular vesicles, probiotic, gut microbiota, diarrhea, pig, immunomodulation