Antibacterial effects of the lectin from pomegranate sarcotesta (PgTeL) against Listeria monocytogenes.

AIMS: To investigate the effects of the lectin from Punica granatum sarcotesta (PgTeL) on growth, viability, cell structure, biofilm formation and chitinase activity of Listeria monocytogenes. In addition, the effect of PgTeL on the adhesion and invasion of human cells (HeLa) was determined. METHODS AND RESULTS: PgTeL showed bacteriostatic and bactericidal effects on the strains L. monocytogenes N53-1 and EGD-e, causing morphometric alterations, cell aggregation, strong deformation and cell disruption. PgTeL inhibited biofilm formation by EGD-e and N53-1 and also interfered with the adhesion and invasion processes of EGD-e and N53-1 in HeLa cells. Finally, the chitinase activity of L. monocytogenes EGD-e was reduced in the presence of PgTeL, which can be involved in the inhibition of adhesion process. CONCLUSION: PgTeL is an antibacterial agent against L. monocytogenes, inhibiting growth and promoting cell death, as well as impairing biofilm formation and bacterial adhesion and invasion into human cells. SIGNIFICANCE AND IMPACT OF THE STUDY: The results stimulate future investigations on the potential of PgTeL for protection of contamination in food products.

Anti-staphylococcal effects of Myracrodruon urundeuva lectins on nonresistant and multidrug resistant isolates.

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.