Unveiling the Neem (Azadirachta indica) Effects on Biofilm Formation of Food-Borne Bacteria and the Potential Mechanism Using a Molecular Docking Approach

Ghada Abd-Elmonsef Mahmoud; Nahed M Rashed; Sherif M El-Ganainy; Shimaa H Salem

doi:10.3390/plants13182669

Unveiling the Neem (Azadirachta indica) Effects on Biofilm Formation of Food-Borne Bacteria and the Potential Mechanism Using a Molecular Docking Approach

Plants (Basel). 2024 Sep 23;13(18):2669. doi: 10.3390/plants13182669.

Authors

Ghada Abd-Elmonsef Mahmoud¹, Nahed M Rashed^{2

3}, Sherif M El-Ganainy^{2

4}, Shimaa H Salem¹

Affiliations

¹ Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut 71516, Egypt.
² Department of Arid Land Agriculture, College of Agricultural and Food Sciences, King Faisal University, P.O. Box 420, Al-Ahsa 31982, Saudi Arabia.
³ Horticulture Department, Faculty of Agriculture, Damietta University, Damietta 34519, Egypt.
⁴ Plant Pathology Research Institute, Agricultural Research Center, Giza 12619, Egypt.

Abstract

Biofilms currently represent the most prevalent bacterial lifestyle, enabling them to resist environmental stress and antibacterial drugs. Natural antibacterial agents could be a safe solution for controlling bacterial biofilms in food industries without affecting human health and environmental safety. A methanolic extract of Azadirachta indica (neem) leaves was prepared and analyzed using gas chromatography-mass spectrometry for the identification of its phytochemical constituents. Four food-borne bacterial pathogens (Bacillus cereus, Novosphingobium aromaticivorans, Klebsiella pneumoniae, and Serratia marcescens) were tested for biofilm formation qualitatively and quantitatively. The antibacterial and antibiofilm properties of the extract were estimated using liquid cultures and a microtiter plate assay. The biofilm inhibition mechanisms were investigated using a light microscope and molecular docking technique. The methanolic extract contained 45 identified compounds, including fatty acids, ester, phenols, flavonoids, terpenes, steroids, and antioxidants with antimicrobial, anticancer, and anti-inflammatory properties. Substantial antibacterial activity in relation to the extract was recorded, especially at 100 μg/mL against K. pneumoniae and S. marcescens. The extract inhibited biofilm formation at 100 μg/mL by 83.83% (S. marcescens), 73.12% (K. pneumoniae), and 54.4% (N. aromaticivorans). The results indicate efficient biofilm formation by the Gram-negative bacteria S. marcescens, K. pneumoniae, and N. aromaticivorans, giving 0.74, 0.292, and 0.219 OD at 595 nm, respectively, while B. cereus was found to have a low biofilm formation potential, i.e., 0.14 OD at 595 nm. The light microscope technique shows the antibiofilm activities with the biofilm almost disappearing at 75 μg/mL and 100 μg/mL concentrations. This antibiofilm property was attributed to DNA gyrase inhibition as illustrated by the molecular docking approach.

Keywords: antibacterial; human pathogens; leaves; natural products; neem; phytochemicals.

Grants and funding

The authors extend their appreciation to the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research, King Faisal University, Saudi Arabia, for funding the publishing of this research work (Project number: Grant KFU241677).