Moringa oleifera seed preparations containing the lectin WSMoL inhibit growth, cell aggregation, and biofilm production of Listeria monocytogenes.

This work evaluated the antibacterial properties of aqueous extract (AE), protein-rich fraction (PF), and isolated water-soluble lectin (WSMoL) from Moringa oleifera Lam. seeds against the gram-positive bacterium Listeria monocytogenes, which causes listeriosis. Foodborne bacterial infections, which are facilitated by biofilm formation, pose significant public health threats. Listeriosis is an infection that involves bacteremia, meningitis, or meningoencephalitis. The strains N53-1 and EGD-e were assessed in this work. Bacteriostatic and bactericidal effects on planktonic cells were assessed by broth microdilution assay and flow cytometry. Possible combined effects with antibiotics (ciprofloxacin and cephalexin) were also determined, as well as the impact of all preparations on bacterial aggregation and biofilm formation. AE, PF and WSMoL presented minimum inhibitory concentration (MIC) ranging from 250 to 300 μg/mL for N53-1, and between 150 and 250 μg/mL for EGD-e. AE and WSMoL did not show bactericidal action but PF was bactericidal to EGD-e (minimal bactericidal concentration: 1500 μg/mL). AE, PF, and WSMoL demonstrated synergistic effects with ciprofloxacin, while AE and PF were synergic together with cephalexin. Moreover, AE, PF and WSMoL showed an inhibitory effect on aggregation of cells of both strains. At 0.97 μg/mL, WSMoL inhibited 95 % the biofilm formation by N53-1, while PF at 4.68 μg/mL elicited a biofilm inhibition of 87 % on the same strain. The data stimulate more studies assessing the potential of crude and purified preparations from M. oleifera containing the lectin WSMoL to combat the causer of listeriosis, as synergistic agents and as aggregation inhibitors.