Design, synthesis, and biological evaluation of β-lactam antibiotic-based imidazolium- and pyridinium-type ionic liquids

We herein report the preparation and investigation of antibacterial activity of biocidal ionic liquids (ILs) consisting of cationic imidazolium or pyridinium and an anionic β-lactam antibiotic. The antibacterial properties were quantified by measuring the minimum inhibitory concentration and minimum bactericidal concentration against Escherichia coli O157:H7, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecium. In general, the ILs had improved antibacterial activity than their parent materials, whether individually or in combination. In 83% of the experiments, the ampicillin ILs (Amp-ILs) had better antibacterial activities than their quaternary halide parent materials, whereas in 92% of the experiments, Amp-ILs outperformed the commercially available sodium ampicillin salt. Amp-ILs had up to 43 times improved antibacterial activity than sodium ampicillin. Overall, when normalized for ampicillin content, ILs had greater antimicrobial activity against E. coli O157:H7, K. pneumoniae, S. aureus, and E. faecium than sodium ampicillin alone.