The antibacterial efficacy of disinfectants used for infection control

Abstract

Healthcare associated infections (HAIs) account for hundreds of millions of infections worldwide every year. Chemical disinfectants are relied upon globally as a primary method of infection control, with this dependence likely to be further reinforced with the continually rising prevalence of antimicrobial resistance. Mitigating the impact of HAIs will require making improvements to current infection control measures, which can only be made once potential limitations have been elucidated.
Concerns regarding the use of disinfectants have been raised in terms of bacterial tolerance development and the ability for bacteria to adopt various survival-related behavioural responses, such as the viable but nonculturable (VBNC) state. In addition, many commercial disinfectant products consist of formulations of multiple active antimicrobials, with the central axiom being that the presence of more mechanisms of action must enhance the efficacy of the product and mitigate bacterial tolerance development. However, little scientific research has been conducted interrogating these assumed beneficial interactions. This project aims to elucidate the aforementioned limitations associated with the use of chemical disinfectants that are commonly used as an infection control measure.
Synergistic interactions between disinfectants were found to be uncommon, species-dependant and on the threshold of the synergism classification, while Klebsiella pneumoniae was found to be able to develop tolerance to individual disinfectants and a combined disinfectant formulation through the acquisition of adaptations and induction into the VBNC state. Molecular mechanisms of tolerance to a range of common disinfectants were identified through a multi-omics approach, allowing the identification of novel mechanisms of disinfectant tolerance demonstrated by K. pneumoniae.
These data demonstrate that HAI-associated pathogenic bacteria are able to adapt to low-level disinfectant exposure, and disinfectant formulations provide minimal benefits over disinfectants used individually in terms of tolerance development and VBNC induction. These data highlight limitations regarding our understanding and attitudes towards the disinfectants which are relied upon heavily across the world every day.
Finally, this project marks the initial development of a novel methodology of direct VBNC quantification and isolation. Currently, VBNC research is limited and restricted by the highly flawed methods used, so further development of this promising novel methodology may provide new opportunities to expand our understanding of the VBNC state as a whole.

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Identifiers

ORCID for Daniel Noel: orcid.org/0000-0001-8560-4441

ORCID for Sandra Wilks: orcid.org/0000-0002-4134-9415

ORCID for Charles Keevil: orcid.org/0000-0003-1917-7706

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