In Vitro Evaluation of the Potentiating Effects of Plant-Derived Molecules on Conventional Biocides

Abstract

Developing innovative and efficient approaches to enhance the antimicrobial activity of conventional biocides is a promising strategy for improving microbial control for healthcare disinfection purposes. In this context, we describe a detailed protocol for evaluating the potentiating effects of plant-derived phytochemicals on synthetic biocides. These plant-based products are attractive candidates as biocide adjuvants due to their structural diversity, bioactivity, and often lower toxicity. The workflow here described allows for the determination of minimum bactericidal concentrations (MBCs) and the systematic generation of both dose-response and time-response curves for each product tested individually (biocides and phytochemicals) and for their dual or triple combinations. The resulting data allow for advanced mathematical modelling, including determining the fractional bactericidal concentration index (FBCI) and assessing the interactions between the tested products regarding synergistic, additive, or antagonistic effects using the software Combenefit. In that sense, it is possible to identify promising natural products as biocide enhancers, optimize antimicrobial efficacy, and design more sustainable and safer disinfection strategies that may reduce the concentrations required of synthetic biocides. This improves microbial control and minimizes environmental and public health risks associated with excessive biocide use.