Impact on bacterial membranes and membrane bound proteins of treatment with chlorhexidine in aqueous and alcohol solutions: Insights from molecular simulations and nuclear magnetic resonance.

Abstract

Lipid membranes form bacteria and enveloped viruses first line of defence against harmful molecules in their environment, whilst also containing proteins crucial to their function. Understanding their properties represents an important step towards developing targeted antimicrobial strategies, such as those employed to protect against infection and spread of pathogens. The most common component in hand sanitizers is alcohol, which is known to kill some pathogens via destruction of their lipid envelope. This is a leading theory for the mode of action of chlorhexidine, a widely used sanitizer in operating theatres. Although the effectiveness of these sanitizer components is well established, the exact way in which they partition into membranes and induce their disruption is unclear. Furthermore, it has been proposed that a significant portion of the disruptive effect of polar sanitizer components such as alcohol may also arise from their denaturing effect upon membrane bound proteins. Since many other sanitizer components are similarly chaotropic, this may be a common shared but often overlooked mechanism. Here, we report on the partitioning behaviour and key interactions of common sanitizer molecules using molecular dynamics (MD) simulations at all atom and coarse-grained resolution, alongside nuclear magnetic resonance (NMR) experiments. We explore the impact of these sanitizer components upon the envelope membranes and associated proteins of both Gram-positive and Gram-negative bacteria, as well as viruses. We find that the partitioning interactions of these sanitizer components are transient, however they consistently take similar positions and conformations. Collectively, this work sheds light on the modes of action of sanitizers across different classes of microbial envelope, and has the potential to identify sites on their associated proteins at which resistant mutations may emerge.