Antibacterial and anti-adhesive properties of ionic liquids with various cationic and anionic heads toward pathogenic bacteria

Abstract

Antimicrobial and anti-adhesive properties of broad range of 1-Butyl-3-methylimidazolium ionic liquids (ILs) were investigated in our previous work. Since the biological properties of ILs have been one of the most highly debated topics and because of low information on the biological behavior of ILs, a supplementary study was performed to find antibacterial and anti-adhesive activity of many other important ILs. Therefore, imidazolium and pyridinium based ionic liquids including [HMIM][I], [HMIM][PF6], [HMIM][Cl], [HMIM][BF4], [HMIM][NTF2], [HMIM][PTS], [HDMIM][BF4], [HMIM][NO3], [HPY][NO3], [BPY][NO3], [OMIM][NO3] and [BMIM][NO3] were selected for this study. Antibacterial and anti-adhesive activities of these ILs were evaluated against a wide range of pathogenic bacteria namely Staphylococcus aureus, Klebsiella pneumoniae, Salmonella typhimurium, Pseudomonas aeruginosa, Escherichia coli, Bacillus tequilensis and Bacillus subtilis. Agar disk diffusion, agar well diffusion and minimum inhibitory concentration (MIC) analyses as well as minimum bactericidal concentration (MBC) were used for determination of antimicrobial activity. Anti-adhesive activity was investigated by 96 well microtiter plate assay. All the ionic liquids showed antibacterial activity against mentioned microorganism. However, [OMIM][NO3] showed the strongest antibacterial activity because of its long alkyl chain length. Among 1-Hexyl-3-methylimidazolium based ILs, [HMIM][NO3] presented the best antibacterial activity. [HPY][NO3] was on the other hand the strongest growth inhibitor among pyridinium based ILs. In addition, the result of the anti-adhesive activity showed that although [HPY][NO3] exhibited the best anti-adhesive activity, not all ionic liquids have anti-adhesive activity.