Evaluation of the antimicrobial activity of pyrithione-based ionic liquids

Abstract The development of new disinfection strategies has become increasingly important over the past decades. One substance that is already used as a potent antimicrobial is pyrithione (2-mercaptopyridine N-oxide), a derivate of naturally occurring aspergillic acid. Even though pyrithione has already proved successful as an antimicrobial, it has some major disadvantages. These include ineffectiveness against viruses and bacteriostatic activity as opposed to bactericidal. A promising approach to address these disadvantages is to incorporate pyrithione into ionic liquids (ILs), to strengthen or physically modify its effects that could portend new applications. This study therefore investigated the antimicrobial properties of pyrithione-based ILs by applying a tripartite test system, including enzyme inhibition tests, virucidal activity determination against three model viruses and activity against eleven clinically relevant bacteria and two yeasts. Results confirm that pyrithione remains an effective antimicrobial even in IL form. A typical “sidechain effect” was demonstrated at the enzymatic level and it was possible to prepare ILs with antiviral properties against all three model viruses. Furthermore, at the bacterial level, this study revealed additional characteristics after incorporating pyrithione into an IL: improved diffusion of pyrithione through agar, a bactericidal effect, especially against gram-negative bacteria and a high susceptibility against clinically relevant yeast Candida tropicalis. These observations demonstrate benefits of pyrithione-IL combinations. Efficacy of pyrithione-based ILs against viruses, bacteria and yeast is particularly worthy of future investigation.