Application of biocides; here surface disinfection – what happens if some microorganisms survive the treatment?
Source: BAM
Biocides are important products to control unwanted microorganisms. For example, disinfectants are a main group of biocidal products that are key to ensure hygiene and to prevent infections. In addition, biocidal products of the main group ‘preservatives’ are crucial to prevent material deterioration and to enable a multitude of industrial processes. In many biocidal applications, the products are intended to kill the microorganisms, as opposed to solely prevent them from growing. This is especially the case for disinfectants, but also for some types of preservatives.
Previous work has shown that the application of disinfectants bears the risk to promote the evolution of microorganisms that are more likely to survive disinfection. It is also known that a fraction of microbial cells within a population of genetically identical cells can survive much longer than others, which can lead to unexpected failure of disinfection. The extent of this heterogeneity in microbial populations exposed to disinfection and the consequences for resistance evolution were hitherto unknown.
In this paper, the death kinetics of a microorganism (the bacterium Escherichia coli) exposed to different disinfectants were measured with high temporal resolution. Using a mathematical model to analyze the death kinetics, it was found that for a specific set of disinfectants, including isopropanol and quaternary ammonium compounds, a fraction of individual cells survived the disinfection, increasing the risk for disinfection failure. Next, the authors hypothesized that this heterogeneous survival in the bacterial population promotes the occurrence of genetic changes upon repeated exposure, allowing the bacteria to evade disinfection. To test this hypothesis, a series of evolution experiments were conducted, in which bacteria were repeatedly exposed to different disinfectants in lethal concentrations. Interestingly, the authors found that bacteria were more likely to evolve higher survival towards those disinfectants for which the model initially predicted a high level of heterogenous survival. Conversely, no evolution of disinfectant resistance to substances that initially showed low heterogeneity was observed.
This study will help to improve strategies for the application of biocides in different settings to avoid application failures due to heterogeneity within bacterial populations and to mitigate the evolution of resistance, ensuring sustained efficacy of biocides on the long term.
Heterogeneous survival upon disinfection underlies evolution of increased tolerance.
Nordholt N, Sobisch L, Gödt A, Lewerenz D, Schreiber F.
Microbioly Spectrum, 2024