Outer membrane vesicles (OMVs) are small, non-replicative, immunogenic spherical bodies secreted by both commensal and pathogenic Gram-negative bacteria such as E. coli. OMVs contain components of the parent bacterium such as DNA, RNA, peptidoglycan, protein, toxins, and lipopolysaccharides (LPS), which act as pathogen-associated molecular patterns (PAMPs).