The synergy of tea tree oil nano-emulsion and antibiotics against multidrug-resistant bacteria

AIMS

We determined the synergistic effects of tea tree essential oil nano-emulsion (nanoTTO) and antibiotics against multidrug-resistant (MDR) bacteria in vitro and in vivo. Then, the underlying mechanism of action of nanoTTO was investigated.

METHODS AND RESULTS

Minimum inhibitory concentrations and fractional inhibitory concentration index (FICI) were determined. The transepithelial electrical resistance (TEER) and the expression of tight junction (TJ) protein of IPEC-J2 cells were measured to determine the in vitro efficacy of nanoTTO in combination with antibiotics. A mouse intestinal infection model evaluated the in vivo synergistic efficacy. Proteome, adhesion assays, quantitative real-time PCR, and scanning electron microscopy were used to explore the underlying mechanisms. Results showed that nanoTTO was synergistic (FICI ≤ 0.5) or partial synergistic (0.5 < FICI < 1) with antibiotics against MDR Gram-positive and Gram-negative bacteria strains. Moreover, combinations increased the TEER values and the TJ protein expression of IPEC-J2 cells infected with MDR Escherichia coli. The in vivo study showed that the combination of nanoTTO and amoxicillin improved the relative weight gain and maintained the structural integrity of intestinal barriers. Proteome showed that type 1 fimbriae d-mannose specific adhesin of E. coli was downregulated by nanoTTO. Then, nanoTTO reduced bacterial adhesion and invasion and inhibited the mRNA expression of fimC, fimG, and fliC, and disrupted bacterial membranes.

Moringa oleifera leaf polysaccharide alleviates experimental colitis by inhibiting inflammation and maintaining intestinal barrier

The characteristic of ulcerative colitis (UC) is extensive colonic mucosal inflammation. Moringa oleifera (M. oleifera) is a medicine food homology plant, and the polysaccharide from M. oleifera leaves (MOLP) exhibits antioxidant and anti-inflammatory activity. The aim of this study to investigate the potential effect of MOLP on UC in a mouse model as well as the underlying mechanism. Dextran sulfate sodium (DSS) 4% in drinking water was given for 7 days to mice with UC, at the same time, MOLP (25, 50, and 100 mg/kg/day) was intragastric administered once daily during the experiment. Structural analysis revealed that MOLP had an average molecular weight (Mw) of 182,989 kDa and consisted of fucose, arabinose, rhamnose, galactose, glucose, xylose, mannose, galactose uronic acid, glucuronic acid, glucose uronic acid and mannose uronic acid, with a percentage ratio of 1.64, 18.81, 12.04, 25.90, 17.57, 12.01, 3.51, 5.28, 0.55, 1.27, and 1.43%, respectively. In addition, the features of MOLP were identified by Fourier-transform infrared (FT-IR) and spectra, X-ray diffraction (XRD). The results showed that MOLP exhibited protective efficacy against UC by alleviating colonic pathological alterations, decreasing goblet cells, crypt destruction, and infiltration of inflammatory cells caused by DSS. Furthermore, MOLP notably repressed the loss of zonula occludens-1 (ZO-1) and occludin proteins in mucosal layer, as well as up-regulating the mRNA expression of interleukin-10 (IL-10) and peroxisome proliferator-activated receptor-γ (PPAR-γ), whereas down-regulating the activation of Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor-kappa B (NF-κB) signaling pathway and the production of pro-inflammatory cytokines. Therefore, these results will help understand the protective action procedure of MOLP against UC, thereby providing significance for the development of MOLP.

Tea Tree Oil Nanoemulsion Potentiates Antibiotics against Multidrug-Resistant Escherichia coli

Extensive efforts are underway to overcome the rising prevalence of antibiotic resistance. Combination therapy may be a potential method to treat multidrug-resistant (MDR) bacterial infections. In this study, tea tree essential oil (TTO) nanoemulsion (nanoTTO) was used in combination with antibiotics to kill microbes. Results showed that nanoTTO enhanced the activities of multiple antibiotics against MDR Escherichia coli (E. coli), and its antimicrobial activity was not changed against bacteria that were cultured in the presence of nanoTTO for 30 passages. Further studies to visualize and quantify intracellular antibiotics concentrations identified that nanoTTO increased the drug accumulation in MDR E. coli by disrupting outer and inner membranes and inhibiting the AcrAB-TolC efflux pump involved in membrane permeability. In addition, nanoTTO was effective in enhancing antibiotic efficacy in the Galleria mellonella infection model and mouse peritonitis model, suggesting a potential strategy against MDR bacterial infections.