Avaliação do potencial antibacteriano do óleo essencial de Melaleuca alternifolia e associação sinérgica ciprofloxacino

Abstract

The discovery and availability of new antimicrobials has been decreasing a lot over the years, in addition to resistance to antibiotics for clinical use, which is recognized by the WHO as the greatest threat in the treatment of infections. Because of this, it has become necessary to seek new strategies to remedy these public health problems. Plants have secondary metabolites that are the biggest target of science in this regard because they act as the plant's defense system and can be extracted in the form of essential oils and often possess antimicrobial capacity. Along with the discovery of new compounds with antimicrobial capacity, new tactics for the treatment of infections are sought and the combined use of antimicrobials for clinical use together with herbal medicines in search of a synergistic effect has shown to be very promising. The objective of this work was to evaluate the antibacterial activity of Melaleuca alternifolia essential oil (TTO) and to investigate the possibility of it’s having a synergistic effect with ciprofloxacin on bacterial strains of Escherichia coli (ATCC 25922, NP 0022, LB 25922 and a strain of Clinical Isolate) and Staphylococcus aureus (ATCC 25923, NP 0038, NP 0023 and B4). The evaluation of the antibiotic potential was performed by the disc-diffusion test, which demonstrated that the strains tested are sensitive to TTO and ciprofloxacin (CIP). The strains were submitted to the MIC test, through the dilution test in microplates, which has the purpose of knowing the concentration/percentage necessary to inhibit growth, the minimum inhibitory concentrations found were between 0.10- 0.50% (937-4500 μg /mL) for TTO and 0.001- 0.012% (10-120 μg/mL) for CIP. After the inhibitory concentrations were known, the checkerboard assay was performed, which associates the two compounds at subinhibitory concentrations. The test showed a strong synergistic effect between all the evaluated associations, after performing the calculations of the fractional inhibitory concentration index (IFIC), it was verified that between 3,3 and 40 times the TTO concentration and 2,3 and 8,3 times the concentration of CIP to have the same antibacterial effect. Complementary studies both in vitro and in vivo must be carried out in order to elucidate the mechanisms of action of the compounds used in this research.