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Thymol (THY) was found to have in vitro antifungal activity against 24 fluconazole (FLC)-resistant and 12 FLC-susceptible clinical isolates of Candida albicans, standard strain ATCC 10231 and one experimentally induced FLC-resistant C. albicans S-1. In addition, synergism was observed for clinical isolates of C. albicans with combinations of THY-FLC and THY-amphotericin B (AMB) evaluated by the chequerboard microdilution method. The interaction intensity was determined by spectrophotometry for the chequerboard assay, and the nature of the interactions was assessed using two non-parametric approaches [fractional inhibitory concentration index (FICI) and DE models]. The interaction between THY-FLC or THY-AMB in FLC-resistant and -susceptible strains of C. albicans showed a high percentage of synergism by the FICI method and the DE method. The DE model gave results consistent with FICI, and no antagonistic action was observed in the strains tested.

BackgroundFood safety is an important worldwide public health concern, and microbial contamination in foods not only leads to food deterioration and shelf life reduction but also results in economic losses and disease.ObjectiveThe main aim of the present study was to evaluate the effect of epsilon-poly-L-lysine (ε-PL) and citral combination against Escherichia coli O157:H7 (E. coli O157:H7) strains. The preliminary antioxidant and antitumor activities were also studied.DesignSynergism is a positive interaction created when two compounds combine and exert an inhibitory effect that is greater than the sum of their individual effects. The synergistic antimicrobial effect of ε-PL and citral was studied using the checkerboard method against E. coli O157:H7. The minimal inhibitory concentration, time-kill, and scanning electron microscope assays were used to determine the antimicrobial activity of ε-PL and citral alone or in combination; 2,2-diphenyl-1-picrylhydrazyl-scavenging assay and western blotting were used in antioxidant activity assays; cell viability assay was carried out to finish preliminary antitumor test.ResultsMinimal inhibitory concentrations of ε-PL and citral resisted to the five E. coli O157:H7 strains were 2–4 µg/mL and 0.5–1 µg/mL, and the fractional inhibitory concentration indices were 0.25–0.375. The results of time-kill assay revealed that a stronger bactericidal effect in a laboratory medium might be exerted in the combination against E. coli O157:H7 than that in a food model. The compounds alone or in combination exhibited a potential 2,2-diphenyl-1-picrylhydrazyl radical–scavenging activity, and the expression of superoxide dismutase 1 and glutathione peroxidase 1 protein increased. The preliminary antitumor activity effect of the combination was better than ε-PL or citral alone.ConclusionsThese findings indicated that the combination of ε-PL and citral could not only be used as a promising naturally sourced food preservative but also be used in the pharmaceutical industry.

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BackgroundIn epidemic regions of the world, brucellosis is a reemerging zoonosis with minimal mortality but is a serious public hygiene problem. Currently, there are various methods for brucellosis diagnosis, however few of them are available to be used to diagnose, especially for serious cross-reaction with other bacteria.MethodTo overcome this disadvantage, we explored a novel multi-epitope recombinant protein as human brucellosis diagnostic antigen. We established an indirect enzyme-linked immunosorbent assay (ELISA) based on this recombinant protein. 248 sera obtained from three different groups including patients with brucellosis (146 samples), non-brucellosis patients (82 samples), and healthy individuals (20 samples) were tested by indirect ELISA. To evaluate the assay, a receiver-operating characteristic (ROC) analysis and immunoblotting were carried out using these characterized serum samples.ResultsFor this test, the area under the ROC curve was 0.9409 (95 % confidence interval, 0.9108 to 0.9709), and a sensitivity of 88.89 % and a specificity of 85.54 % was given with a cutoff value of 0.3865 from this ROC analysis. The Western blot results indicate that it is feasible to differentiate human brucellosis and non-brucellosis with the newly established method based on this recombinant protein.ConclusionOur results obtained high diagnostic accuracy of the ELISA assay which encourage the use of this novel recombinant protein as diagnostic antigen to implement serological diagnosis of brucellosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1552-9) contains supplementary material, which is available to authorized users.

A checkerboard microdilution method, performed according to the recommendations of the National Committee for Clinical Laboratory Standards, was used to study the in vitro interaction of fluconazole and allicin in 24 fluconazole-resistant clinical isolates of Candida albicans, one experimentally induced strain S-1, and one ATCC type strain 10231. The interaction intensity was determined by spectrophotometric methods and visual reading of the checkerboard assay, and the nature of the interactions was assessed using two nonparametric approaches [fractional inhibitory concentration index (FICI) and DE models]. Synergism was observed in 23 strains using FICI, and in 22 strains using DE. The DE model gave results consistent with FICI, but no antagonistic action was observed. The positive interactions were also confirmed by the time-killing test and agar diffusion in the selected strains. Moreover, the in vivo experiment showed that a combination of fluconazole and allicin exhibited a good synergism against C. albicans.

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BackgroundThe targeting of Staphylococcus aureus biofilm structures are now gaining interest as an alternative strategy for developing new types of antimicrobial agents. Magnolol (MOL) shows inhibitory activity against S. aureus biofilms and Triton X-100-induced autolysis in vitro, although there are no data regarding the molecular mechanisms of MOL action in bacteria.Methodology/Principal FindingsThe molecular basis of the markedly reduced autolytic phenotype and biofilm inhibition triggered by MOL were explored using transcriptomic analysis, and the transcription of important genes were verified by real-time RT-PCR. The inhibition of autolysis by MOL was evaluated using quantitative bacteriolytic assays and zymographic analysis, and antibiofilm activity assays and confocal laser scanning microscopy were used to elucidate the inhibition of biofilm formation caused by MOL in 20 clinical isolates or standard strains. The reduction in cidA, atl, sle1, and lytN transcript levels following MOL treatment was consistent with the induced expression of their autolytic repressors lrgA, lrgB, arlR, and sarA. MOL generally inhibited or reversed the expression of most of the genes involved in biofilm production. The growth of S. aureus strain ATCC 25923 in the presence of MOL dose-dependently led to decreases in Triton X-100-induced autolysis, extracellular murein hydrolase activity, and the amount of extracellular DNA (eDNA). MOL may impede biofilm formation by reducing the expression of cidA, a murein hydrolase regulator, to inhibit autolysis and eDNA release, or MOL may directly repress biofilm formation.Conclusions/SignificanceMOL shows in vitro antimicrobial activity against clinical and standard S. aureus strains grown in planktonic and biofilm cultures, suggesting that the structure of MOL may potentially be used as a basis for the development of drugs targeting biofilms.