Mechanistic Study of the Kinetic Phenomena Influencing the Bacteriostatic Action of Silver Ions in Agar Bioassays.

Louis Cornette De Saint Cyr,Azariel Ruiz Valencia,Guillaume Ramadier,Jean-Pierre Méricq,Laurence Soussan

doi:10.3390/antibiotics10040368

Abstract

Bacteriostatic action of a biocidal agent results from the cumulative impact of different kinetics, including those of bacterial growth, mass transfer of the agent and its antibacterial action against the targeted bacteria. Current studies on bacteriostatic effects always directly consider the combination of these kinetics at given times, without discrimination between each other. This work introduces a novel approach, consisting of first studying independently, by the experiment and the model, the different kinetics involved, and then in coupling these kinetics to obtain a model that will be confronted with experimental data. An agar diffusion test with silver ions against Escherichia coli bacteria was implemented herein to assess the relevance of this approach. This work achieved to characterize the different kinetics and to propose a dynamic model combining them, which fits the experimental data with a silver diffusivity in the biofilm fixed to 7.0 ± 0.1 × 10−12 m2 s−1. This study also proves that the diffusive phenomenon was limiting the bacteriostatic action of silver ions over the test duration.

Highlights

Pure bacterial growth, and pure antibacterial action of silver ions will be first decoupled and characterized by both experience and model to propose consistent kinetic models for each of this phenomenon. These kinetics will be combined in a global model that will be compared to experimental data
The diffusion of the antibacterial agent (Ag+ ) in the agar exempt of bacteria was first studied in order to test the reliability for this specific application of both the COMSOL
This study proposes an original approach and modeling to determine the diffusivity of silver ions in a bacterial biofilm and to fully characterize each phenomenon occurring during the bacteriostatic action of silver ions in an agar diffusion test

Summary

Introduction

Bacteriostatic action, i.e., the inhibition of bacterial growth, is useful, and required in numerous application fields, such as drug delivery to prevent tissue infections (e.g., antibacterial plasters), inhibition of biofilm formation on food packaging, or on membranes used for water and air treatments [1,2,3,4,5,6,7]. The bacteriostatic efficiency depends on several factors, such as the antibacterial agent used, its concentration, the bacterial strains, the bacterial concentration involved, and the kinetics (i.e., transport of the bacteriostatic agent, bacterial growth and antibacterial action), resulting in a certain contact time between bacteria and the antibacterial agent [8]. A too slow transport of the biocidal agent may not prevent bacteria from growing since bacteria can multiply faster than they die. It is very important to determine kinetics of antibacterial agent transfer, bacterial growth, and antibacterial action

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