Aims
To evaluate the anti‐staphylococcal effects of lectins isolated from bark (MuBL), heartwood (MuHL) and leaves (MuLL) of Myracrodruon urundeuva.
Methods and Results
The lectins were evaluated for: effects on growth, aggregation, haemolytic activity and biofilm‐forming ability of Staphylococcus aureus clinical isolates nonresistant (8325‐4) and multidrug resistant (LAC USA300); interference with the expression of virulence genes (hla, rnaIII and spa) of the Agr system of S. aureus; and synergistic effect with the antibiotics cefoxitin and cefotaxime. MuBL, MuHL and MuLL reduced growth (minimal inhibitory concentration (MIC): 12·5–50 µg ml−1) and viability (minimal bactericidal concentration (MBC): 100 µg ml−1) of 8325‐4 and LAC USA300 cells. MuLL (at ½MIC and MIC) reduced LAC USA300 agglutination. The lectins did not interfere with haemolytic activity and expression of hla, rnaIII and spa genes. Only MuHL was able to reduce the biofilm production by 8325‐4 (50–400 µg ml−1) and LAC USA300 (400 µg ml−1).
Conclusion
The M. urundeuva lectins showed antibacterial activity against nonresistant and resistant clinical isolates of S. aureus and synergistic effects with antibiotics in reducing growth and biofilm formation.
Significance and Impact of the Study
This work reports bioactive molecules capable of acting as anti‐staphylococcal agents, since there are increasing reports of multiresistant isolates of this bacterium.
BACKGROUND: Lectins from Moringa oleifera seeds (WSMoL), Myracrodruon urundeuva bark (MuBL), and heartwood (MuHL) are larvicidal agents against Aedes aegypti; in addition, WSMoL is an ovicidal agent against this mosquito. In this work, we evaluated the ovicidal activity of MuBL and MuHL by determining the concentrations that reduce the hatching rates by 50% in 72 h (EC 50 ). The effects of WSMoL, MuBL, and MuHL on the ultrastructure of the eggs' surface were assessed by scanning electron microscopy (SEM). In addition, the ability of these lectins to penetrate the eggs was investigated by using conjugates of the lectins with fluorescein isothiocyanate (FITC).
RESULTS: MuBL andMuHL were ovicidal agents with EC 50 of 0.26 and 0.80 mg/mL (260 and 800 ppm), respectively. SEM images of eggs treated with WSMoL for 24 h revealed discontinuity of the exochorionic network and the absence of the exochorionic cells and their tubercles. After 48 and 72 h of incubation, strong deformation and degeneration of egg surfaces were observed. In MuBL and MuHL-treated eggs, the presence of lumps on the surface of the eggs, disappearance of the exochorionic network and the decrease and deformation of tubercles were observed. Lastly, fluorescence microscopy revealed that the three lectins were able to enter the eggs and reach the digestive tract of the embryos. CONCLUSION: WSMoL, MuBL, and MuHL are ovicidal agents on A. aegypti that have differing efficiencies in terms of how they cause alterations in the chorionic surface and in terms of their ability to penetrate the eggs.
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