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.

Eugenol alleviates Salmonella Typhimurium-infected cecal injury by modulating cecal flora and tight junctions accompanied by suppressing inflammation.

BACKGROUND: Salmonella enterica serovar Typhimurium (ST) mainly exists in poultry and poultry related products, which are common sources of human salmonellosis. So, ST is an important zoonotic pathogen that threatens public health and safety. Eugenol has been noted for its antibacterial and anti-inflammatory properties, and it is expected to develop into an antibacterial therapy in vivo. METHODS: Herein, the effects of eugenol against ST infection in terms of intestinal flora, cecal tight junction, and cecal inflammation in broilers was evaluated in this study. RESULTS: The results showed that oral eugenol pretreatment obviously relieved the histopathological changes and ultrastructural injury of cecum caused by ST infection. Further analysis found that eugenol lessened the number of ST in the cecum, restrained Proteobacteria and Ruminococcus, and kept the ratio of Firmicutes to Bacteroidetes (F/B), improved the relative abundance of Alistipes compared to the infection control. Moreover, eugenol sustained the expression of ZO-1, claudin-1, and occluding tight junction proteins, reduced the mRNA levels of myeloid differentiation factor 88 (MyD88), toll-like receptor-4 (TLR4) and inducible nitric oxide synthesis (iNOS), suppressed the phosphorylation of p65 and IκBα in the NF-κB signaling pathway, as well as the mRNA levels of TNF-α, IL-1ß, IL-2, and IL-18 in the cecum tissue. CONCLUSION: Taken together, eugenol could protect broilers against ST infection via maintaining intestinal flora, tight junctions involved in mucosal barrier function, then accordingly limiting the excessive inflammation, finally contributed to improving relative weight gains and survival rates of broilers.

Bactericidal activity of gallic acid against multi-drug resistance Escherichia coli.

The continuous emergence of multidrug-resistant (MDR) bacteria has posed an increasingly serious public health threat which urges people to develop some alternatives. Gallic acid (GA) is a natural ingredient in many traditional Chinese medicines, which has many biological activities, such as antibacterial, and antiseptic. Here, clinical isolates of MDR Escherichia coli (E. coli) were used to evaluate the antibacterial effect of GA and the underlying mechanism. The results revealed that GA exerted bactericidal activity and inhibited the formation of bacterial biofilm. GA enhanced the activities of ceftiofur sodium or tetracycline against E. coli, and facilitated antibiotic accumulation in bacteria. Further analysis of morphological alterations and efflux pump gene expressions confirmed that GA damaged outer and inner membranes, and suppressed the mRNA expressions of acrA, acrB, tolC, acrD and acrF involved in membrane permeability. In addition, GA showed protective effects against bacterial infection and improved the survival rates of Galleria mellonella and BALB/c mice. These data highlight a better understanding of GA against bacteria and provide an alternative strategy for MDR bacterial infection.

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.

Effect of the bacterial community on the volatile flavour profile of a Chinese fermented condiment - Red sour soup - During fermentation.

Red sour soup (RSS) is a traditional fermented seasoning used by people in Guizhou Province, China. The volatile compounds were detected by gas chromatography ion mobility spectrometry (GC-IMS), while the bacterial community compositions were revealed by 16S sequencing. A total of 70 volatile substances were assessed, and esters, terpenes, and alcohols played a dominant role in RSS. Lactic acid bacteria (LAB) were dominant in the microbial community. During fermentation, multiple volatile flavour substances and various LAB were mainly derived from the secondary fermentation stage. The core bacteria with an important influence on volatile flavour substances were analysed by the Mantel test, identifying Bacteroides, Lactobacillus, Lactococcus, Enterobacteriaceae, Pantoea, Clostridium, Enterobacter, unclassified genera, Caproiciproducens, Nitriliruptoraceae, Halomonas, Bradyrhizobium, Pediococcus, Caulobacteraceae, Weissella, Ligilactobacillus, and Levilactobacillus and et al.. This study provides us with useful information about flavour-generating bacteria among RSS fermentation periods. The abundances of these bacteria may be controlled to enrich the desired flavour metabolites while eliminating unwanted metabolites.

The protective effect and potential mechanisms of eugenol against Salmonella in vivo and in vitro.

Salmonella enterica serovar Typhimurium (S. Typhimurium) continues to be a serious concern to the poultry industry as a bacterial foodborne zoonosis, which generally results in intestinal inflammation and barrier dysfunction or even death. Eugenol is a phenolic compound with various pharmacological activities involved antioxidant, anti-inflammatory, and antibacterial effects, which is expected to be an effective nonantibiotic therapy. The purpose of this study was to explore the protective effects of eugenol in the cellular and broiler models of S. Typhimurium infection and the possible underlying mechanisms. The results of animal infection showed that eugenol treatments enhanced the relative weight gains and survival rates of broilers with a reduction of the organ bacterial load and intestinal ultrastructural injury. Moreover, eugenol significantly inhibited the mRNA levels of myeloid differentiation factor 88 (MyD88) and toll-like receptor-4 (TLR4), then declined the phosphorylation of p65 and IκBα of NF-κB pathway and the expressions of inflammatory factors (TNF-α, IL-1ß, IL-2, and IL-18) in duodenum tissues, while maintained the expressions of intestinal tight junction proteins (ZO-1, claudin-1, occludin). Further experiments in vitro revealed that eugenol markedly inhibited the adhesion and invasion of S. Typhimurium to RAW264.7 or IEC-6 cells, then reduce bacterial multiplication in IEC-6 or DF-1 cells. In conclusion, eugenol could defend broilers from S. Typhimurium infection by stabilizing the intestinal mucosal barrier and relieving inflammatory response, as well as inhibiting bacterial adhesion and invasion to cells.

Eugenol exposure in vitro inhibits the expressions of T3SS and TIF virulence genes in Salmonella Typhimurium and reduces its pathogenicity to chickens.

BACKGROUND: Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common food-borne pathogen, which has the ability to infect a wide range of hosts. The increasing emergence of drug-resistant strains urgently requires new alternative therapies. Eugenol has been shown to be very effective against drug-resistant strains of Gram-negative and Gram-positive bacteria. The purpose of this study is to explore the effects of eugenol on the virulence factors and pathogenicity of S. Typhimurium. METHODS: The antibacterial activity of eugenol was investigated via the changes of cell morphology, fimbriae related-genes and virulence factors of S. Typhimurium, then the pathogenicity of S. Typhimurium pretreated by eugenol to chickens was evaluated. RESULTS: Susceptibility testing showed that eugenol possessed significant antimicrobial activity. Scanning electron microscope analysis showed eugenol treatment deformed the morphology with damaged fimbriae structure of S. Typhimurium. Real time PCR assay confirmed eugenol significantly down-regulated the expressions of virulence factors (hilA, hilD, sipA, sipC, spiC, misL) of Type III secretion system (T3SS) and adherence genes (fimA, fimH, fimD, fimY, fimZ, stm0551) of Type I fimbriae (TIF). Animal experiment proved that the pathogenicity of S. Typhimurium exposed by eugenol was reduced, which was evidenced by the higher survival rate, weight gains and organs indexes, the lower bacterial loads in organs. Meanwhile, the duodenal histopathological changes were mitigated, with a significantly decline in the expressions of TNF-α, IL-6 and IL-18. CONCLUSION: In summary, eugenol pretreatment may alleviate the pathogenicity of the S. Typhimurium to chickens via wrecking the fimbriae and inhibiting the mRNA expressions of virulence factors and adhesion molecules. These data dedicated the potential mechanisms of eugenol against S. Typhimurium in vitro.

Hydrothermal-template synthesis and electrochemical properties of Co3O4/nitrogen-doped hemisphere-porous graphene composites with 3D heterogeneous structure.

Despite the high capacity of Co3O4 employed in lithium-ion battery anodes, the reduced conductivity and grievous volume change of Co3O4 during long cycling of insertion/extraction of lithium-ions remain a challenge. Herein, an optimized nanocomposite, Co3O4/nitrogen-doped hemisphere-porous graphene composite (Co3O4/N-HPGC), is synthesized by a facile hydrothermal-template approach with polystyrene (PS) microspheres as a template. The characterization results demonstrate that Co3O4 nanoparticles are densely anchored onto graphene layers, nitrogen elements are successfully introduced by carbamide and the nanocomposites maintain the hemispherical porous structure. As an anode material for lithium-ion batteries, the composite material not only maintains a relatively high lithium storage capacity (the first discharge specific capacity can reach 2696 mA h g-1), but also shows significantly improved rate performance (1188 mA h g-1 at 0.1 A g-1, 344 mA h g-1 at 5 A g-1) and enhanced cycling stability (683 mA h g-1 after 500 cycles at 1 A g-1). The enhanced electrochemical properties of Co3O4/N-HPGC nanocomposites can be ascribed to the synergistic effects of Co3O4 nanoparticles, novel hierarchical structure with hemisphere-pores and nitrogen-containing functional groups of the nanomaterials. Therefore, the developed strategy can be extended as a universal and scalable approach for integrating various metal oxides into graphene-based materials for energy storage and conversion applications.