Bacterial acquisition of antimicrobial resistance (AMR) genes via horizontal gene transfer (HGT) has contributed to the rise in superbugs globally. Although there are multiple known mechanisms used by bacteria to transfer AMR, a less explored mechanism involves bacterial membrane vesicles (MVs). Bacterial MVs are released by all bacteria as part of their normal growth and are rich in DNA. In this study we examined the contribution of pathogenic and microbiota-derived bacterial MVs to the spread of AMR.
We found that MVs produced by Pseudomonas aeruginosa and Escherichia coli contain DNA encoding for AMR, and that P. aeruginosa cultures treated with sub-lethal doses of antibiotics produced more MVs. We identified that MVs containing AMR genes were capable of mediating HGT, resulting in antibiotic resistant P. aeruginosa and Helicobacter pylori transformants, highlighting the ability of MVs to facilitate HGT and promote the spread of AMR.
The human gut microbiome is a known reservoir for AMR, where it is thought that HGT occurs frequently. The ability of MVs to contribute to HGT of AMR genes within the human gut microbiome remains unknown. Therefore, we aimed to investigate the ability of microbiota-derived MVs to contain AMR and mediate HGT. To do this, we purified MVs from a mixed human gut microbiome culture consisting of 95 isolates obtained from healthy individuals. We found that sub-lethal doses of antibiotics increased MV production by these cultures, with increased packaging of nucleic acids that was protected from DNase treatment. We are currently sequencing the DNA within microbiota-derived MVs using Next Generation sequencing to determine whether they contain AMR genes, in addition to determining their ability to mediate HGT. Collectively, these studies will advance our limited knowledge regarding the contribution of bacterial MVs in the transfer of AMR genes in a physiological setting such as the human microbiota.