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

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.