Ampicillin triggers the release of Pal in toxic vesicles from Escherichia coli

•The bacterial lipoprotein, Pal, is released from Escherichia coli under certain conditions and has been shown to contribute to sepsis-related inflammation.•Ampicillin, a β-lactam antibiotic, enhances the release of Pal lipoprotein from Escherichia coli to a greater extent than two other non-β-lactam antibiotics (gentamicin and levofloxacin).•It is proposed that the majority of Pal is released from E. coli in outer membrane vesicles, which also contain lipopolysaccharides and other toxic/inflammatory molecules. In addition to lipopolysaccharides (LPS), outer membrane proteins – Lpp, OmpA and peptidoglycan-associated lipoprotein (Pal) – are part of the outer membrane of Escherichia coli and are proposed to contribute to bacterial sepsis-related inflammation. This study showed that ampicillin (a β-lactam antibiotic) enhances Pal's release from Escherichia coli to a greater extent than gentamicin and levofloxacin (aminoglycoside and quinolone antibiotics, respectively). It is proposed that the majority of Pal is released in outer membrane vesicles (OMVs), which also contain LPS and other outer membrane and periplasmic proteins. The OMVs were purified by ultracentrifugation and characterised by transmission electron microscopy and nanoparticle tracking analysis, and Pal and other E. coli proteins were detected by Western blot. It also proposed that sepsis treatments using certain β-lactam antibiotics may further aggravate the over-exuberant inflammatory response by enhancing the release of Pal and LPS in OMVs. [Display omitted]