Antibacterial and antiadhesive properties of butyl-methylimidazolium ionic liquids toward pathogenic bacteria

Abstract

Interest in ionic liquids (ILs) for their potential in different areas is increasing, as they are claimed to possess a range of bioactive properties, which may be exploited in the design of antibacterial and antiadhesive compounds. However, quantitative information on the antimicrobial and antiadhesive properties of ILs is very scarce. This paper reports, for the first time, on a comprehensive study into the antibacterial and antiadhesive activity of a broad range of 1-butyl-3-methylimidazolium ILs including [BMIM][N(CN)₂], [BMIM][PTS], [BMIM][NO₃], [BMIM][SCN], [BMIM][I], [BMIM][Cl], [BMIM][PF₆], [BMIM][MeOSO₃], [BMIM][HSO₄], [BMIM][BF₄] and [BMIM][NTf₂] against a wide range of pathogenic and semi-pathogenic, Gram positive and Gram negative bacteria. These pathogens include P. aeruginosa, S. aureus, E. coli, B. cereus, B. subtilis, S. typhimurium, and K. pneumonia. Antimicrobial activity was comprehensively evaluated qualitatively and quantitatively using agar disk diffusion assay, agar well diffusion assay as well as determining Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Antiadhesive activity was also evaluated using a 96 well microtiter plate assay. The results of the study demonstrated that almost all ILs have antimicrobial activity against mentioned pathogens, however in different degrees. Among them, the IL with NTf₂ anion showed very strong antimicrobial activity against all pathogens. ILs with HSO₄ and SCN anions were also great antimicrobials. Weak antimicrobial activity was observed for the IL with PTS anion. In addition, not all ionic liquids showed antiadhesive activity.