Outer membrane vesicles (OMVs) are proteoliposomes blebbed from the surface of Gram-negative bacteria. Once regarded as cell debris or microscopy artefacts, these spherical membrane structures (20-300 nm in diameter) are now thought to play a significant role in microbial virulence. By investigating OMVs from oral bacteria Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia and from antibiotic susceptible and multi-drug resistant (MDR) bacteria Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae we have found that OMVs play a significant role in bacterial virulence. Bacterial OMVs were found to bind to and be phagocytosed by monocytes, M(naïve) and M(IFNγ) macrophages induce NFκB activation and increase TNFα, IL-8 and IL-1β cytokine secretion. OMVs were found to provide both priming and activation of the inflammasome complex and high resolution microscopy and flow cytometry showed that P. gingivalis OMVs primed and activated macrophage inflammasomes in vivo. OMVs were found to induce differential but in general strong TLR2 and TLR4-specific responses and moderate responses in TLR7, TLR8, TLR9, NOD1 and NOD2 expressing-HEK-Blue cells. Further, OMVs were found to stimulate autophagy induction and the secretion of pro-inflammatory cytokines/chemokines TNFα, IL-1β and IL-8 in epithelial cells (OKF6s), fibroblasts (HGFs) and endothelial cells (HuVECs), as well as induce apoptosis/cell death at higher OMV concentrations. Finally, MDR-OMVs bound and induced greater disruption of epithelial cell-tight-junctions, which enhanced bacterial migration in vitro and mice pre-treated with OMVs had significantly higher levels of bacteremia. In conclusion, OMVs were found to enhancing colonisation/invasion of host tissue while dysregulating immune responses to the respective bacteria.