How are resistance, tolerance and the like defined? ’Tolerance‘ refers to the ability of micro-organisms to survive temporary exposure to normally lethal concentrations of an antimicrobial agent. This may or may not be inherited. Rather, the transient nature of the ability needs to be emphasised. This means that prolonged exposure to an agent could kill tolerant bacteria. Resistance, on the other hand, is the inherited ability to survive normally lethal concentrations of the agent, regardless of the duration of exposure. Disinfectants and antibiotics are fundamentally different Disinfectants are usually used at concentrations well above the minimum inhibitory concentration (MIC) of bacteria, whereas antibiotics are dosed as high as necessary (efficacy) and as low as possible (patient comfort) [2]. In addition, disinfectants only work for seconds to hours. As a result, bacteria in contact with disinfectants have little time to arm themselves by adapting. In addition, disinfectants usually have a non-specific effect, e.g. destroying the bacterial membrane. In contrast, antibiotics often target individual metabolic pathways [4]. Antibiotic therapy also usually uses only one active ingredient, while disinfectants often consist of combinations of active ingredients [5]. Low risk of bacterial adaptation to disinfectants The differences show that research on antibiotics cannot simply be transferred to disinfectants. Even if genuine resistance to disinfectants cannot be ruled out, the risk is low if disinfectants are used correctly [1]. What do these terms mean in relation to disinfectants? Resistance or tolerance? The term ’resistance‘ is well known in the context of antibiotics. But what about resistance to disinfectants? To understand that this is not usually true resistance, the terms need to be clarified. A review article from the HARTMANN SCIENCE CENTER addresses this issue [1]. In it, the team distinguishes between definitions from antibiotic and disinfectant research and provides an assessment of the risk of ’true’ disinfectant resistance. KNOWLEDGE References Krewing M et al. (2024) J Hosp Infect 150: 51-60. https://doi.org/10.1016/j.jhin.2024.05.006 Abel Zur Wiesch P et al.(2017) PLoS Comput Biol 13: e1005321. https://doi.org/10.1371/journal.pcbi.1005321 Huet AA et al. (2008) Microbiology 154: 3144-3153. https://doi.org/10.1099/mic.0.2008/021188-0 Noel DJ et al.(2021) mBio 12: e0228121. https://doi.org/10.1128/mBio.02281-21 Exposure time Mode of action Composition Concentration Antibiotics and disinfectants differ in... 5
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