Kinetics of Bacterial Adaptation, Growth, and Death at Didecyldimethylammonium Chloride sub-MIC Concentrations

Adrián Pedreira; José A Vázquez; Míriam R García

doi:10.3389/fmicb.2022.758237

Kinetics of Bacterial Adaptation, Growth, and Death at Didecyldimethylammonium Chloride sub-MIC Concentrations

Front Microbiol. 2022 Apr 7:13:758237. doi: 10.3389/fmicb.2022.758237. eCollection 2022.

Authors

Adrián Pedreira^{1

2}, José A Vázquez², Míriam R García¹

Affiliations

¹ Biosystems and Bioprocess Engineering (Bio2Eng), Marine Research Institute-Spanish National Research Council (IIM-CSIC), Eduardo Cabello, Vigo, Spain.
² Group of Recycling and Valorization of Waste Materials (REVAL), Marine Research Institute-Spanish National Research Council (IIM-CSIC), Eduardo Cabello, Vigo, Spain.

Abstract

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) are standard indexes for determining disinfection effectiveness. Nevertheless, they are static values disregarding the kinetics at sub-MIC concentrations where adaptation, growth, stationary, and death phases can be observed. The understanding of these dynamic mechanisms is crucial to designing effective disinfection strategies. In this study, we studied the 48 h kinetics of Bacillus cereus and Escherichia coli cells exposed to sub-MIC concentrations of didecyldimethylammonium chloride (DDAC). Two mathematical models were employed to reproduce the experiments: the only-growth classical logistic model and a mechanistic model including growth and death dynamics. Although both models reproduce the lag, exponential and stationary phases, only the mechanistic model is able to reproduce the death phase and reveals the concentration dependence of the bactericidal/bacteriostatic activity of DDAC. This model could potentially be extended to study other antimicrobials and reproduce changes in optical density (OD) and colony-forming units (CFUs) with the same parameters and mechanisms of action.

Keywords: B. cereus; E. coli; bactericidal; bacteriostatic; didecyldimethylammonium chloride (DDAC); disinfection; dynamic modeling; sub-MIC concentration.