Atividade antibacteriana de plantas medicinais frente á bactérias multirresistentes e a sua interação com drogas antimicrobianas

Abstract

Infection control of the multidrug-resistant microorganisms sometimes is ineffective even with the development of new antibiotics. Many herbal extracts have antimicrobial effects and may represent an alternative therapy for infectious diseases, mainly when associated with antibiotics of clinical use. The aim of this study was to evaluate the antibacterial activity of medicinal plants in multidrug-resistant microorganisms and their interaction with antimicrobial agents. We evaluate the antibacterial activity of plant extracts and fractions of Eleutherine plicata (“marupazinho”) Geissospermum vellosii (“pau-pereira”) and Portulaca pilosa (“amor-crescido”) against isolates of Oxacillin-Resistant Staphylococcus aureus (ORSA) and multi-resistant bacteria Pseudomonas aeruginosa, from human clinical isolates. Also we evaluate interaction of these plant extracts with antimicrobial agents of clinical use. The antibacterial activity was determined by disk diffusion on Mueller Hinton agar and the Minimum Inhibitory Concentration (MIC) by micro dilution plate technique using Muller Hinton broth as culture medium and 0.01% resazurin as a developer of bacterial growth. The extracts and fractions were tested at concentrations of 500, 250, 125, 62.5, 31.2 and 16.2 μg/mL dissolved in 10% DMSO. Plants E. plicata and G. vellosii demonstrated activity against ORSA isolates with MICs of 125 μg/mL, whereas P. pilosa had an effect on the isolates of P. aeruginosa with MIC of 250 μg/mL. There were 25% of synergism and only 5% of antagonism of all 120 plant and antimicrobial agents interaction tested. ORSA isolates had synergistic interaction with ciprofloxacin, clindamycin and vancomycin agents and with both plant derivatives of E. plicata and G. vellosii. The derivatives of P. pilosa potentiated the action of the aztreonam, cefepime and piperacillin + tazobactam agents compared to the isolates of P. aeruginosa multidrug-resistant. The results shows therapeutic potential of E. plicata, G. vellosii and P. pilosa in the control of bacterial infections involving multidrug-resistant phenotype (MDR) and its interaction with antibacterial agents may represent a new alternative in the therapy of these infections.