Disinfectant test in biofilms: natural against chemical sanitizers

Main target of this work is to explore/delineate the bactericidal properties of natural product mixtures as disinfectants of plant origin. For this purpose, the disinfectant activity of essential oil [1], decoction and hydrosol of Satureja thymbra were tested against bacterial biofilms comparatively with the action of various known chemical decontaminating solutions. Thus, the activities of seven decontaminating solutions were determined against the following five bacterial species (grown either as monospecies or as mixed culture biofilms): Staphylococcus simulans and Lactobacillus fermentum (useful bacteria), Pseudomonas putida (spoilage bacterium), Salmonella enterica and Listeria monocytogenes (pathogenic bacteria). The quantification of their antimicrobial actions was performed using the bead vortexing method, followed by agar plating and/or by conductance measurements (via the metabolic activity of biofilm cells).

Salmonella enterica was determined as the least sensitive bacteria against the action of the decontaminating solutions in conductance measurements, followed by P. putida, S. simulans, L. monocytogenes and L. fermentum grown as monospecies biofilm. On the other hand, the essential oil and hydrosol of S. thymbra caused the most pronounced log-reduction of bacterial cells on both types of biofilms (monospecies or mixed culture). The observed activity was superior when compared with known chemical decontaminating solutions.

In conclusion, the use of essential oils and their by-products as alternative means of cleaning contaminated surfaces presents an intriguing case which by further development may provide potent disinfecting solutions of natural origin.

References: 1. Chorianopoulos, N. et al. (2006)J. Agric. Food Chem. 54: 3139–3145