Avaliação dos efeitos antimicrobianos do extrato salino e lectina de folhas de Schinus terebinthifolia Raddi sobre Staphylococcus

Abstract

Bacteria of the genus Staphylococcus are considered important pathogens for human and veterinary medicine. The formation of biofilm by these isolates is a virulence factor that hinders the treatment of infections, stimulating the search for alternative control strategies. The saline extract of leaves of Schinus terebinthifolia (ES) and the lectin isolated from it (SteLL) have previously reported antimicrobial action. The objectives of this dissertation were: 1. Carry out a narrative review on the action of compounds of plant origin against agents that cause mastitis; 2. To investigate the effect of ES on strains of Staphylococcus isolated from caprine mastitis and 3. To evaluate the antibacterial potential of SteLL against isolates of S. aureus sensitive (UFPEDA 02) and resistant to oxacillin (UFPEDA 670). Previously published studies were accessed in the main databases and a review article was constructed, considering the main mechanisms of antimicrobial action of plant compounds. S. terebinthifolia leaves were homogenized in 0.15M NaCl to obtain ES and SteLL was isolated by chitin column chromatography. The effect of ES on the growth and survival of mastitis strains isolated from S. aureus (Sa24, Sa32) or Staphylococcus sp. (Ssp1 and Ssp2) was evaluated by determining the minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations. Then, the growth curve of the isolates was determined. The antibiofilm activity of ES was investigated by the crystal violet method. The synergistic potential of ES with carbapenem and cephalexin antibiotics was also evaluated. Additionally, the MIC and MIC of SteLL against UFPEDA 02 and UFPEDA 670 were determined and the viability of bacterial cells was investigated by flow cytometry. The antibiofilm potential of SteLL was also evaluated. The review revealed that the toxicity of plant antimicrobials for causing mastitis may mainly involve damage to the cell wall, lipid peroxidation, alteration of transmembrane potential, oxidative stress, formation of membrane pores and morphometric changes that lead to apoptosis or increase in cell permeability. Antibiofilm activity may result from inhibition of adhesion of microorganisms, interference with autoinductive quorum sensing signals and/or degradation of the exopolymeric matrix. ES inhibited the growth of Sa24, Sa32, Ssp1 and SSp2 (CMI of 1800, 900, 450 and 225 μg/mL, respectively) but did not interfere with the survival of the isolates. Biofilm formation by all isolates was impaired by ES. In addition, ES also exerted a synergistic action in combination with antibiotics against all isolates. SteLL was a bacteriostatic and bactericidal agent for UFPEDA 02 and UFPEDA 670 with CMI of 12.5 and 25 μg/mL and CMB of 50 and 100 μg/mL, respectively. SteLL inhibited growth in a dose-dependent manner and altered morphometric parameters related to cell size, shape and complexity of sensitive and resistant strains, as well as inhibiting biofilm formation. In conclusion, ES is an antimicrobial agent as it affects growth and biofilm formation by mastitis isolates, and the toxicity of SteLL to S. aureus involves inhibition of growth, induction of cell death and inhibition of biofilm formation.