Anti-biofilm activity of biochanin A against Staphylococcus aureus.

Biofilm-forming Staphylococcus aureus can easily accumulate on various food contact surfaces which induce cross-contamination and are difficult to eliminate in the food industry. This study aimed to evaluate the anti-biofilm effects of natural product biochanin A against S. aureus. Results showed that biochanin A effectively eradicated established S. aureus biofilms on different food-contact materials. Fluorescence microscopic analyses suggested that biochanin A disintegrated the established biofilms by dissociate extracellular polymeric substance (EPS) in matrix. In addition, biochanin A at the sub-MIC concentration also effectively inhibited the biofilm formation by regulating the expression of biofilm-related genes (icaA, srtA, eno) and suppressing the release of EPS in biofilm matrix. Molecular docking also demonstrated that biochanin A conducted strong interactions with biofilm-related proteins (Ica A, Sortase A, and Enolase). These findings demonstrated that biochanin A has the potential to be developed as a potent agent against S. aureus biofilm in food industries. KEY POINTS: • Anti-biofilm effect of biochanin A against S. aureus was revealed for the first time. • Biofilm of S. aureus on various food-contact surfaces were efficiently eradicated. • Biochanin A prevented S. aureus biofilm formation via reducing EPS production.

Phenotype and RNA-seq-Based transcriptome profiling of Staphylococcus aureus biofilms in response to tea tree oil.

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that causes a wide range of diseases, including food poisoning. Tea tree oil (TTO), an essential oil distilled from Melaleuca alternifolia, is well-known for its antibacterial activities. TTO effectively inhibited all 19 tested strains of S. aureus biofilm and planktonic cells. Phenotype analyses of S. aureus biofilm cells exposed to TTO were performed by biofilm adhesion assays, eDNA detection and PIA release. RNA sequencing (RNA-seq) was used in our study to elucidate the mechanism of TTO as a potential antibacterial agent to evaluate differentially expressed genes (DEGs) and the functional network in S. aureus ATCC 29213 biofilms. TTO significantly changed (greater than a 2- or less than a 2-fold change) the expression of 304 genes in S. aureus contained in biofilms. The levels of genes related to the glycine, serine and threonine metabolism pathway, purine metabolism pathway, pyrimidine metabolism pathway and amino acid biosynthesis pathway were dramatically changed in the biofilm exposed to TTO. Furthermore, the expression changes identified by RNA-seq analysis were verified by real-time RT-PCR. To the best of our knowledge, this research is the first study to report the phenotype and expression profiles of S. aureus in biofilms exposed to TTO.

Antibacterial activity and mode of action of totarol against Staphylococcus aureus in carrot juice.

Food contaminated with pathogenic bacteria such as Staphylococcus aureus (S. aureus), represents a serious health risk to human beings. Totarol is an antibacterial novel phenolic diterpenes. In present study, the antibacterial activity of totarol against S. aureus was investigated in a food system. The antibacterial activity of totarol was determined by measuring the zones of inhibition and minimum inhibitory concentrations (MICs). The MICs for S. aureus strains were in the range of 2-4 µg/ml. The probable antibacterial mechanism of totarol was the alteration in cell membranes integrity and permeability, which leading to the leakage of cellular materials. The electric conductivity showed a time- and dose-dependent increasing manner, and we utilized totarol to induce the production of cytoplasmic ß-galactosidase in S. aureus. Scanning electron microscopy and transmission electron microscopy analysis further confirmed that S. aureus cell membranes were damaged by totarol. The time-kill assay and detection of the kinetics of S. aureus deactivation in situ indicated that totarol has good preservative activities in a food model. Totarol successfully inhibited S. aureus development in carrot juice, at room temperature (25 °C) and in refrigerator (4 °C) respectively. Our works provided not only additional evidences in support of totarol being regarded as a natural antibacterial food preservative but also fundamental understanding on the mode of antibacterial action. It is necessary to consider that totarol will become a promising antibacterial additive for food preservative.

A novel multi-epitope recombined protein for diagnosis of human brucellosis.

BACKGROUND: In 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. METHOD: To 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. RESULTS: For 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. CONCLUSION: Our 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.

Aptamer-based fluorescent screening assay for acetamiprid via inner filter effect of gold nanoparticles on the fluorescence of CdTe quantum dots.

This paper reports a novel aptamer-based fluorescent detection method for small molecules represented by acetamiprid based on the specific binding of aptamers with acetamiprid, and the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (CdTe QDs). When CdTe QDs were mixed with AuNPs, the fluorescence of CdTe QDs was significantly quenched via IFE. The IFE efficiency could be readily modulated by the absorption and the aggregation state of AuNPs. The presence of salt could easily induce the aggregation of AuNPs, resulting in the fluorescence recovery of the quenched QDs. Acetamiprid-binding aptamer (ABA) could adsorb on the negatively charged AuNPs through the coordination interaction to protect AuNPs from salt-induced aggregation, so the fluorescence of CdTe QDs would be quenched by the IFE of AuNPs. However, the specific binding of ABA with acetamiprid could release the ABA from the surfaces of AuNPs and decrease the salt tolerance of AuNPs, so the IFE-decreased fluorescence of CdTe QDs was regained with the presence of acetamiprid, and the fluorescence enhancement efficiency was driven by the concentration of acetamiprid. Based on this principle, the aptamer-based fluorescent method for acetamiprid has been established and optimized. The assay exhibited excellent selectivity towards acetamiprid over its analogues and other pesticides which may coexist with acetamiprid. Under the optimum experiment conditions, the established method could be applied for the determination of acetamiprid with a wide linear range from 0.05 to 1.0 µM, and a low detection limit of 7.29 nM (3σ). Furthermore, this IFE-based method has been successfully utilized to detect acetamiprid in six types of vegetables, and the results were in full agreement with those from HPLC and LC-MS. The proposed method displays remarkable advantages of high sensitivity, rapid analysis, excellent selectivity, and would be suitable for the practical application of target screening in real samples.

In vitro antimicrobial activity of honokiol against Staphylococcus aureus in biofilm mode.

Staphylococcus aureus (S. aureus) can attach to food, host tissues and the surfaces of medical implants and form a biofilm, which makes it difficult to eliminate. The purpose of this study was to evaluate the effect of honokiol on biofilm-grown S. aureus. In this report, honokiol showed effective antibacterial activity against S. aureus in biofilms. S. aureus isolates are capable of producing distinct types of biofilms mediated by polysaccharide intercellular adhesion (PIA) or extracellular DNA (eDNA). The biofilms' susceptibility to honokiol was evaluated using confocal laser scanning microscopy (CLSM) analysis. The transcript levels of the biofilm-related genes, the expression of PIA, and the amount of eDNA of biofilm-grown S. aureus exposed to honokiol were also investigated. The results of this study show that honokiol can detach existing biofilms, kill bacteria in biofilms, and simultaneously inhibit the transcript levels of sarA, cidA and icaA, eDNA release, and the expression of PIA.

Effect of nisin and perilla oil combination against Listeria monocytogenes and Staphylococcus aureus in milk.

In the present study, in vitro interaction of nisin and perilla oil (PO) against 20 food-borne isolates of L. monocytogenes and S. aureus were assessed using a checkerboard microdilution method. Synergism was observed in tested strains with the fractional inhibitory concentration indexs (FICIs) ranges from 0.125-0.25 and 0.19-0.375, respectively. Scanning electron microscopy was carried out to investigate the effect of nisin and PO on the integrity of cell wall and membrane of L. monocytogenes and S. aureus. The results showed that nisin and PO were more effective in damaging cell wall and membrane in combination.

Inhibitory effect of totarol on exotoxin proteins hemolysin and enterotoxins secreted by Staphylococcus aureus.

Staphylococcus aureus (S. aureus) causes a wide variety of infections, which are of major concern worldwide. S. aureus produces multiple virulence factors, resulting in food infection and poisoning. These virulence factors include hyaluronidases, proteases, coagulases, lipases, deoxyribonucleases and enterotoxins. Among the extracellular proteins produced by S. aureus that contribute to pathogenicity, the exotoxins α-hemolysin, staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) are thought to be of major significance. Totarol, a plant extract, has been revealed to inhibit the proliferation of several pathogens effectively. However, there are no reports on the effects of totarol on the production of α-hemolysin, SEA or SEB secreted by S. aureus. The aim of this study was to evaluate the effects of totarol on these three exotoxins. Hemolysis assay, western blotting and real-time reverse transcriptase-PCR assay were performed to identify the influence of graded subinhibitory concentrations of totarol on the production of α-hemolysin and the two major enterotoxins, SEA and SEB, by S. aureus in a dose-dependent manner. Moreover, an enzyme linked immunosorbent assay showed that the TNF-α production of RAW264.7 cells stimulated by S. aureus supernatants was inhibited by subinhibitory concentrations of totarol. Form the data, we propose that totarol could potentially be used as a promising natural compound in the food and pharmaceutical industries.

Complete genome sequence of Escherichia coli O157:H7 lytic phage JL1.

A novel virulent phage named JL1 against Escherichia coli O157:H7 was isolated from raw sewage. It was found that JL1 has an icosahedral head and a long flexible non-contractile tail. The complete genome of JL1 is composed of a linear double-stranded DNA of 43,457 base pairs in length, with 54.77 % G+C content and 60 putative open reading frames. Morphology and bioinformatics analysis revealed that phage JL1 is a member of the family Siphoviridae of the order Caudovirales. It is different from previously reported phages of E. coli O157:H7 but is homologous to Sodalis phage SO-1, Shigella phage EP23, Escherichia phage HK578 and Escherichia phage SSL-2009a.

Inhibitory Effect of Non-Saccharomyces Starmerella bacillaris CC-PT4 Isolated from Grape on MRSA Growth and Biofilm.

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious pathogen with biofilm-forming and drug-resistant properties that make it difficult to eradicate. In this study, the inhibition of MRSA (ATCC 43300) by Starmerella bacillaris CC-PT4 (CGMCC No. 23573) was evaluated. The results showed that the inhibition of MRSA growth and biofilm was caused by S. bacillaris CC-PT4 cell-free supernatant (CFS). The CFS of S. bacillaris CC PT4 at different times can effectively inhibit the formation of MRSA biofilm, remove the preformed biofilm, and down-regulate the related genes that promote the formation of biofilm. Afterwards, untargeted metabolomics was performed to analyze the CFS of S. bacillaris CC-PT4. Several molecules with antibacterial and inhibitory biofilm effects from the CFS were found, one of which, 2-amino-1-phenylethanol (APE), has not been reported to have antiMRSA ability before. In this study, molecular docking analysis and in vitro experiments were used to verify the function of APE to inhibit MRSA. These results indicate that S. bacillaris CC-PT4 CFS can effectively inhibit MRSA which has potential application value in controlling MRSA.

Allicin-induced global gene expression profile of Saccharomyces cerevisiae.

To understand the response mechanisms of fungus cells upon exposure to the natural fungicide allicin, we performed commercial oligonucleotide microarrays to determine the overall transcriptional response of allicin-treated Saccharomyces cerevisiae strain L1190. Compared with the transcriptional profiles of untreated cultures, 147 genes were significantly upregulated, and 145 genes were significantly downregulated in the allicin-treated cells. We interpreted the microarray data with the hierarchical clustering tool, T-profiler. Major transcriptional responses were induced by allicin and included the following: first, Rpn4p-mediated responses involved in proteasome gene expression; second, the Rsc1p-mediated response involved in iron ion transporter activity; third, the Gcn4p-mediated response, also known as general amino acid control; finally, the Yap1p-, Msn2/4p-, Crz1p-, and Cin5p-mediated multiple stress response. Interestingly, allicin treatment, similar to mycotoxin patulin and artificial fungicide thiuram treatment, was found to induce genes involved in sulfur amino acid metabolism and the defense system for oxidative stress, especially DNA repair, which suggests a potential mutagenicity for allicin. Quantitative real-time reverse transcription-polymerase chain reaction was performed for selected genes to verify the microarray results. To our knowledge, this is the first report of the global transcriptional profiling of allicin-treated S. cerevisiae by microarray.

Microarray analysis of p-anisaldehyde-induced transcriptome of Saccharomyces cerevisiae.

p-Anisaldehyde (4-methoxybenzaldehyde), an extract from Pimpinella anisum L. seeds, is a potential novel preservative. To reveal the possible action mechanism of p-anisaldehyde against microorganisms, yeast-based commercial oligonucleotide microarrays were used to analyze the genome-wide transcriptional changes in response to p-anisaldehyde. Quantitative real-time RT-PCR was performed for selected genes to verify the microarray results. We interpreted our microarray data with the clustering tool, T-profiler. Analysis of microarray data revealed that p-anisaldehyde induced the expression of genes related to sulphur assimilation, aromatic aldehydes metabolism, and secondary metabolism, which demonstrated that the addition of p-anisaldehyde may influence the normal metabolism of aromatic aldehydes. This genome-wide transcriptomics approach revealed first insights into the response of Saccharomyces cerevisiae (S. cerevisiae) to p-anisaldehyde challenge.

Antibacterial Effect of Caprylic Acid and Potassium Sorbate in Combination against Listeria monocytogenes ATCC 7644.

ABSTRACT: Listeria monocytogenes is a common foodborne pathogen that cause life-threatening infection with high mortality rates. Biofilm development of L. monocytogenes decreases its sensitivity to antibiotics, which has long attracted attention globally. Caprylic acid (CA) and potassium sorbate (PS) are both widely used food preservatives, but their synergistic effect against L. monocytogenes has not been described. This study explored the antibacterial activities of the CA-PS combination against L. monocytogenes ATCC 7644 grown in planktonic or biofilm cultures. The fractional inhibitory concentration index values, determined by the checkerboard microdilution method, were 0.37 ± 0.03 and 0.31 ± 0.04, showing their synergistic antimicrobial effects against L. monocytogenes ATCC 7644 in planktonic and biofilm cultures, respectively. CA-PS effectively eradicated the biofilm biomass to 10.8% by crystal violet assay and to 8.63% by fluorescence microscopic analysis compared with the control. The apoptosis rates of microbial cells embedded within biofilm significantly increased to 51.4%. Subsequent analysis revealed that the combination inhibited biofilm formation by affecting extracellular DNA release and polysaccharide intercellular adhesion expression, which was decreased from 8.93 to 1.04 ng of extracellular DNA per relative biomass and to 54.7% of the control, respectively. In addition, the combination inhibited the growth of L. monocytogenes ATCC 7644 by up to 0.67 ± 0.05 and 0.30 ± 0.03 log CFU/cm2 in planktonic and biofilm modes on a carrot surface, respectively. The synergistic antibacterial effects of CA-PS against L. monocytogenes ATCC 7644 were statistically significant, and the combination is an excellent candidate to be a novel food preservative.

Antifungal activity of thymol against clinical isolates of fluconazole-sensitive and -resistant Candida albicans.

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 DeltaE 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 DeltaE method. The DeltaE model gave results consistent with FICI, and no antagonistic action was observed in the strains tested.

Multicolor quantum dot-encoded microspheres for the fluoroimmunoassays of chicken newcastle disease and goat pox virus.

Semiconductor nanocrystals (or quantum dots, QDs) have the potential to overcome some of the limitations encountered by traditional fluorophores in fluorescence labeling applications. The unique spectroscopic properties of QDs make them hold immense promise as versatile labels for biological applications. In this work, we employ the layer-by-layer (LbL) method for the construction of bio-functional multicolor QD-encoded microspheres. Polystyrene microspheres with diameter of 3 microm were used as templates for the deposition of different sized CdTe QDs/polyelectrolyte multilayers. Two different antigens, Chicken newcastle disease (CND) antigen and goat pox virus (GPV) antigen, were conjugated to two kinds of biofunctional multicolor microspheres with different optical encoding. The multicolor microspheres can capture corresponding antibodies labeled with QDs, QDs-CND antibody and QDs-GPV antibody in the fluoroimmunoassays. The microspheres can be distinguished from each other based on their optical encoding.

Global gene expression profile of Saccharomyces cerevisiae induced by dictamnine.

Dictamnine, a natural plant product, has been reported to have antimicrobial activity against bacteria and fungi; however, the dictamnine response mechanisms of microorganisms are still poorly understood. We have shown that dictamnine has antimicrobial activities against the model fungus Saccharomyces cerevisiae, with a minimum inhibitory concentration (MIC) value of 64 microg/ml. Commercial oligonucleotide microarrays were used to determine the global transcriptional response of S. cerevisiae triggered by treatment with dictamnine. We interpreted our microarray data using the hierarchical clustering tool, T-profiler. Several major transcriptional responses were induced by dictamnine. The first was the induced environmental stress response, mainly under the control of the Msn2p and Msn4p transcription factors, and the repressed environmental stress response in genes containing the PAC (RNA polymerase A and C box) and rRPE (ribosomal RNA processing element) motifs. The second was the Upc2p-mediated response involved in lipid biosynthesis. The third comprised the PDR3- and RPN4-mediated responses involved in multidrug resistance (MDR). Finally, the TBP-mediated response was induced with dictamnine treatment. TBP is an essential general transcription factor involved in directing the transcription of genes. Quantitative real-time RT-PCR was performed on selected genes to verify the microarray results. Furthermore, morphological transitions during dictamnine exposure to S. cerevisiae L1190 (MATa/alpha) were examined, using confocal laser microscopy.

Antibacterial activity and mode of action of ε-polylysine against Escherichia coli O157:H7.

Purpose. Gram-negative Escherichia coli O157:H7 were chosen as model bacteria to evaluate the antimicrobial mechanism of ε-polylysine (ε-PL).Methodology. The antibacterial activity of ε-PL was detected by measuring the minimum inhibitory concentration values as well as the time-kill curve. The membrane integrity was determined by ultraviolet (UV) absorption, membrane potential (MP) assay and flow cytometry (FCM) experiments. The permeability of the inner membrane was detected by ß-galactosidase activity assay. Furthermore, electron microscopy [scanning electron microscopy (SEM) and transmission electron microscopy (TEM)] was utilized to observe bacterial morphology.Key findings. These results demonstrated that ε-PL showed its antibacterial activity by changing the integrity and permeability of cell membranes, leading to rapid cell death. The electron microscopy analysis (SEM and TEM) results indicated that the bacterial cell morphology, membrane integrity and permeability were spoiled when the E. coli O157:H7 cells were exposed to minimum inhibitory concentrations of ε-PL (16 µg ml-1). In addition, the bacterial membrane was damaged more severely when the concentration of ε-PL was increased.Conclusion. The present study investigated the antimicrobial mechanism of ε-PL by measuring the content of cytoplasmic ß-galactosidase, proteins and DNA. In addition, SEM and TEM were carried out to assess the mechanism. These results show that ε-PL has the ability to decrease the content of large molecules, cellular soluble proteins and nucleic acids associated with increasing the content of cytoplasmic ß-galactosidase in supernatant by causing damage to the cell membranes. Consequently, the use of ε-PL as a natural antimicrobial agent should eventually become an appealing method in the field of food preservation.

Antioxidative and anticancer properties of Licochalcone A from licorice.

ETHNOPHARMACOLOGICAL RELEVANCE: Licochalcone A (LCA) is a characteristic chalcone that is found in licorice, which is a traditional medicinal plant. In traditional medicine, LCA possesses many potential biological activities, including anti-parasitic, anti-inflammatory and antitumor activities. AIM OF THE STUDY: To determine the antioxidant activity of LCA and, on this basis, to investigate the role of its anticancer activity. MATERIALS AND METHODS: To validate the antioxidant activity of LCA, the proteins SOD, CAT and GPx1 were analyzed using western blotting and cellular antioxidant activity (CAA) assays. Oxidative free radicals are associated with cancer cells. Therefore, the anticancer activity of LCA was also evaluated. To assess the anticancer activity, cell viability assays were performed and apoptosis was evaluated. In addition, MAPK-related proteins were analyzed using western blotting. RESULTS: The experimental data showed that the EC50 of LCA is 58.79±0.05µg/mL and 46.29±0.05µg/mL under the two conditions tested, with or without PBS. In addition, LCA at a concentration of approximately 2-8µg/mL can induce the expression of SOD, CAT and GPx1 proteins. Further, LCA inhibits the growth of HepG2 cells through cell proliferation arrest and the subsequent induction of apoptosis, and LCA attenuated the p38/JNK/ERK signaling pathway in a dose-dependent manner. CONCLUSION: The results showed that LCA suppresses the oxidation of cells and markedly inhibits the proliferation of cancer cells. These findings confirm the traditional use of LCA in folk medicine.

Oleuropein protects L-02 cells against H2O2-induced oxidative stress by increasing SOD1, GPx1 and CAT expression.

Oleuropein (OL), a natural phenolic compound, comprises the major constituent of Olea europea leaves and unprocessed olives, and OL is considered to be the principal components that confer the characteristic taste and stability of olive oil. Oxidative damage induced by H2O2 treatment can irreversibly damage the L-02 cells, resulting in cell death and apoptosis. Whether the effects of oxidative stress could be attenuated in cultured human L-02 cells by incubation with OL is still unknown. In this research, the function of OL in protecting human L-02 cells against H2O2 induced cell death and cell apoptosis was investigated, and the mechanism by which OL underlies the effect was also examed. L-02 cells were exposed to 100µM H2O2 with or without OL pretreatment at different concentrations. Cell viabilities were monitored by WST-1 assay. ALT, AST and LDH production in culture medium were also determined. ROS levels were detected by L-012 chemiluminescence, and OL increased SOD1, CAT and GPx1 expression in a concentration-dependent manner. Further studies showed that OL also inhibited H2O2-induced P38 and JNK phosphorylation but enhanced ERK1/2 phosphorylation in a dose-dependent manner. These findings suggested that OL as a potent antioxidant agent and a natural compound found in several plants, may be exploited as a potentially useful method for hepatopathy prevention.

Antimicrobial, antioxidant, and antitumor activity of epsilon-poly-L-lysine and citral, alone or in combination.

BACKGROUND: Food 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. OBJECTIVE: The 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. DESIGN: Synergism 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. RESULTS: Minimal 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. CONCLUSIONS: These 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.