Antibacterial activity of coinwort cotoneaster (Cotoneaster nummularia) gum extracts on P. aeruginosa and M. luteus strains under optimum conditions

Abstract

Here, antibacterial effects of extracts derived from Cotoneaster nummularia plant and gum, which obtained by the Soxhlet method, were examined on both Micrococcus luteus and Pseudomonas aeruginosa bacterial strains under three independent variables (e.g., solvent type, extraction time, and solvent/sample ratio), response factors of Minimum Inhibitory Concentration, Minimum Bactericidal Concentration, and zone of inhibition (growth inhibition zone). Furthermore, Gram staining technique and biochemical tests were applied to confirm the identification of the genus and species of bacterial strains. Box-Behnken design and Response Surface Methodology (involving 13 defined runs) were also employed to determine the optimal extraction conditions. Then, changes in response variables of the obtained extracts were analyzed for both bacteria. Findings revealed that the antibacterial effects of the examined extracts slightly varied concerning the microorganism strain and solvent type so that the aqueous solvent had the highest efficiency. Additionally, it was observed that the Gram-positive bacterium was more sensitive to the derived extractions than the Gram-negative bacterium. Results of concentration-response curves for Bacillus cereus and Salmonella also confirmed that increasing the time significantly enhanced bacterial growth, and concentrations of the obtained extracts (MICs= 0.25 and 0.5 µg.ml^-1) had notable inhibitory effects on the bacterial growth.