Common Foodborne Pathogenic Bacteria Research Articles

Colorimetric aptasensor for Listeria monocytogenes detection using dual functional Fe3O4@MIL-100(Fe) with magnetic separation and oxidase-like activities in food samples.

A novel colorimetric aptasensor assay based on the excellent magnetic responsiveness and oxidase-like activity of Fe3O4@MIL-100(Fe) was developed. Fe3O4@MIL-100(Fe) absorbed with aptamer and blocked by BSA served as capture probe for selective isolation and enrichment of Listeria monocytogenesone of the most common and dangerous foodborne pathogenic bacteria. The aptamer absorbed on Fe3O4@MIL-100(Fe) was further used as signal probe that specifically binds with target bacteria conjugation of capture probe for colorimetric detection of Listeria monocytogenes, taking advantages of its oxidase-like activity. The linear range of the detection of Listeria monocytogenes was from 102 to 107CFUmL-1, with the limit of detection as low as 14CFUmL-1. The approach also showed good feasibility for detection of Listeria monocytogenes in milk and meat samples. The spiked recoveries were in the range 81-114% with relative standard deviations ranging from 1.28 to 5.19%. Thus, this work provides an efficient, convenient, and practical tool for selective isolation and colorimetric detection of Listeria monocytogenes in food.

A REVIEW OF MICROBIAL SAFETY AND BACTERIAL BIOFILM FORMATION OF FRESH VEGETABLES

Fresh vegetables are usually eaten raw and do not receive any treatment to ensure adequate removal or inactivation of harmful microorganisms prior to eating. Food-borne disease associated with the consumption of fresh vegetables appear to be rising. Farming practices, post-harvest processing and condition of storage have effect on microbial communities for fresh vegetables. Salmonella spp, E. coli, Staphylococcus aureus and Listeria are common foodborne pathogenic bacteria associated with the consumption of fresh vegetables. Biofilm, is characterized as by population of bacteria firmly adhered to a surface and these communities provide longer survival and resistance to adverse conditions such as presence of disinfectants and antibiotics. Attachment of bacteria to plant surface or biofilm formation is the initial step towards the contamination in fresh vegetable. This review emphasizes on pre- and post- harvest contaminant in the safety of fresh vegetables, bacterial biofilm formation and food safety strategies to reduce risk and the foodborne disease outbreaks linked to fresh produce

Antibacterial activity and mechanisms of α-terpineol against foodborne pathogenic bacteria.

This study aimed to evaluate the antibacterial activities of α-terpineol against common foodborne pathogenic bacteria by agar well diffusion, broth microdilution, and colony counting assay. Propulsive research was conducted to reveal the antibacterial mechanisms, including morphology, infrared spectroscopy, membrane fluidity, membrane permeability, proton motive force, and oxidative phosphorylation. Results indicated that the antibacterial activity of α-terpineol decreased in the following order: Escherichia coli O157:H7, Salmonella typhimurium, Listeria monocytogenes, and Staphylococcus aureus. With an initial cell count of 8 log CFU/mL, α-terpineol at 0.8% (v/v) reduced E. coli O157:H7 and S. aureus by approximately 5.6 and 3.9 log CFU/mL within 1 h, respectively. Remarkable destruction in cell envelopes and intracellular organizations was observed. The hydroxyl of α-terpineol might form glycosidic bonds with carbohydrates and hydrogen bonds with PO2- and COO- via infrared spectroscopy analysis. Generalized polarization of Laurdan revealed that the polar head groups of phospholipids transformed into close packed. The anisotropy variations of trimethyl amino-diphenylhexatriene (TMA-DPH) and DPH suggested membrane fluidity decreased. The N-phenyl-1-naphthylamine intake assay indicated that α-terpineol impairedthe cell wall. Propidium iodide staining was indicative of damaged plasma membranes. Electron transport in the cytoplasmic membrane was impaired, inducing reactive oxygen species accumulation. Both membrane electrical potential and membrane pH gradient collapsed. The disruption of proton motive force and the leakage of ATP resulted in a deficit of intracellular ATP. Our research revealed the interaction between the hydroxyl group of α-terpineol and bacteria affects membrane function contributing to the bacteria's death. KEY POINTS: • α-Terpineol hydroxy formed glycosidic bonds and hydrogen bonds with bacteria • α-Terpineol increased the membrane gelation and reduced the membrane fluidity • Proton motive force and oxidative phosphorylation were impaired.

Antimicrobial activity of selected plant extracts against common food borne pathogenic bacteria

Increasing antibiotic resistance of important human pathogens calls for investigation and discovery of new antibiotics. Various medicinal plants and spices available in Fiji have antimicrobial potential against various food-borne pathogens. This research aims to address the assumed antimicrobial activity of twelve selected plant extracts against fifteen food-borne pathogens and to evaluate the pathogens resistances. The Kirby-Bauer Method was used in this study to determine the potency of plant extracts. Total Phenolic Content (TPC) was determined by the Folin-Ciocalteu Spectrophotometric method. The chosen plant species samples used were Morinda citrifolia (noni) leaves, Syzygium aromaticum (clove) bud, Psidium guajava (guava) leaves, Ocimum basilicum (basil) leaves, Carica papaya (pawpaw) leaves, Azadirachta indica (neem) seed oil, Citrus limon (lemon) leaves, and Zingiber officinale (ginger) root. Extracts from these eight plants were tested against common food-borne bacteria; Clostridium perfringens, Citrobacter youngae, Enterobacter aerogenes, Enterobacter amnigenus, Enterobacter cloacae, Escherichia coli, Hafnia alveia, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus vulgaris, Proteus mirabilis, Photobacterium damselae, Raoultella ornithinolytica and Vibrio alginolyticus. Both resistance and antibacterial responses were observed for the different plant extracts. All plant extracts were successful in inhibiting bacterial growth for different number of species at varying levels of effectiveness with noni being the most effective. The highest inhibition zones (ZOI>14 mm) were shown by garlic, basil, jasmine and neem. Highest mean ZOI was shown by noni at 11.4 mm followed by garlic at 10.1 mm and clove at 8.4 mm. Minimum inhibitory concentrations were determined for extracts exhibiting antibacterial potential. TPC may attribute to the antibacterial properties of the extracts, however, this needs further investigation. Results indicate presence of possible bioactive compounds in the extracts which can aid in search for new antibiotic drugs from plant sources. Studies that identify the compounds of therapeutically important flora in Fiji is recommended.

Antibiofilm Efficacy of Quercetin against Vibrio parahaemolyticus Biofilm on Food-Contact Surfaces in the Food Industry.

Vibrio parahaemolyticus, one of the most common foodborne pathogenic bacteria that forms biofilms, is a persistent source of concern for the food industry. The food production chain employs a variety of methods to control biofilms, although none are completely successful. This study aims to evaluate the effectiveness of quercetin as a food additive in reducing V. parahaemolyticus biofilm formation on stainless-steel coupons (SS) and hand gloves (HG) as well as testing its antimicrobial activities. With a minimum inhibitory concentration (MIC) of 220 µg/mL, the tested quercetin exhibited the lowest bactericidal action without visible growth. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin at sub-MICs levels (1/2, 1/4, and 1/8 MIC) against V. parahaemolyticus was examined. Control group was not added with quercetin. With increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of target genes linked to flagellar motility (flaA, flgL), biofilm formation (vp0952, vp0962), virulence (VopQ, vp0450), and quorum-sensing (aphA, luxS) were all dramatically suppressed. Quercetin (0–110 μg/mL) was investigated on SS and HG surfaces, the inhibitory effect were 0.10–2.17 and 0.26–2.31 log CFU/cm2, respectively (p < 0.05). Field emission scanning electron microscopy (FE-SEM) corroborated the findings because quercetin prevented the development of biofilms by severing cell-to-cell contacts and inducing cell lysis, which resulted in the loss of normal cell shape. Additionally, there was a significant difference between the treated and control groups in terms of motility (swimming and swarming). According to our research, quercetin produced from plants should be employed as an antibiofilm agent in the food sector to prevent the growth of V. parahaemolyticus biofilms. These results indicate that throughout the entire food production chain, bacterial targets are of interest for biofilm reduction with alternative natural food agents in the seafood industry.

Advances in Electrochemical Aptamer Biosensors for the Detection of Food‐borne Pathogenic Bacteria

AbstractThe detection of harmful components in food is of paramount importance in the light of recent food safety incidents caused by foodborne pathogenic bacteria. Aptamer electrochemical biosensors are novel biosensors that use electrode modifications to immobilise aptamers, the biological recognition elements, and then use electrochemical techniques to detect the generated electrical signals. Compared with traditional detection methods, electrochemical aptamer sensors have the advantages of high specificity, high sensitivity, and low cost and have been widely used to detect hazardous components in food. This review summarises these sensors′ current research status and problems in detecting common foodborne pathogenic bacteria and provides an outlook on their development trends.

Development of rapid and easy detection of Salmonella in food matrics using RPA-CRISPR/Cas12a method

Salmonella species are common foodborne pathogenic bacteria. At present, most detection methods for Salmonella are unsuitable for on-site applications because they require large instruments or complicated procedures. This study developed a novel method of the on-site detection for Salmonella in food by combining the CRISPR/Cas12a system with recombinant polymerase amplification (RPA). The optimal concentration ratio of Cas12a enzyme, CRISPR RNA (crRNA) and FQ-probe is 1 : 1: 2.5. The detection limit of the RPA–CRISPR/Cas12a method was 1 × 10−4 ng/μL for genomic DNA (gDNA), and 102 CFU/mL for bacterial liquid. The method exhibited no cross-reactivity to 4 common pathogenic bacteria. A simple boiling method was used to pretreat chicken and egg samples to meet on-site testing requirements. The detection limits of chicken and egg samples were 103 CFU/mL initially and could reach 102 CFU/mL and 101 CFU/mL, respectively, after 3 h enrichment at 37 °C. The sensitivity of the RPA–CRISPR/Cas12a method was comparable to that of the quantitative polymerase chain reaction (qPCR) technique. In addition, the operation of this method is simpler and faster than qPCR. Thus, the method is applicable to the on-site detection for Salmonella in food.

ENHANCING THE ANTIBACTERIAL EFFECT OF BACTERIOCIN FROM LACTOCOCCUS LACTIS SUBSP. LACTIS USING CHITOSAN NANOPARTICLES

Chitosan, a cationic polymer derived from the hot alkali deacetylation of chitin, has numerous biological applications with non-toxicity, biocompatibility and biodegradability. Chitosan nanoparticles were prepared and encapsulated with bacteriocin extracted from Lactococcus lactis subsp lactis to produce chitosan nanoparticles conjugate bacteriocin using ionic gelation method. This formulation was examined for its antibacterial activity representing food bio-preservative against Salmonella typhimurium, Escherichiae coli, Bacillus cereus and Staphylococcus aureus, compared with chitosan nanoparticles, crud chitosan and free bacteriocin. Agar diffusion method was applied to evaluate the in-vitro drug release, effect of pH and temperature on its stability. The results revealed that the In-vitro release within 24 hours of chitosan nanoparticles conjugate bacteriocin was controlled by about (79%) with cumulative and sustained effect when compared with free bacteriocin (94%). Chitosan nanoparticles conjugate bacteriocin exhibit the highest antibacterial activity (with significant difference p &lt; 0.05) followed by free bacteriocin and chitosan nanoparticles, while crud chitosan was the lowest representing thermal stability (≤ 70ºC) when subjected to low pH. Gram-positive bacteria were more susceptible than Gram-negative bacteria to all of the components. Chitosan nanoparticles contribute successful safe food preservative enhancement when incorporated with bacteriocin against the common food-borne pathogenic bacteria.

Inactivation of foodborne pathogenic and spoilage bacteria by single and dual wavelength UV-LEDs: Synergistic effect and pulsed operation

As an emerging UV source, UV light-emitting diodes (UV-LEDs) are an attractive alternative to traditional mercury vapor lamps for food decontamination. In this work, we sought to find the strategies for the improvement of UV-LED inactivation efficiencies on common foodborne pathogenic and spoilage bacteria. Inactivation efficiencies of UV-LEDs with peak emissions at 369 nm (UVA), 288 nm (UVB), and 271 nm (UVC) and combined emissions at 369/288, 369/271, and 288/271 nm on three foodborne pathogenic bacteria (Escherichia coli, Staphylococcus epidermidis, Salmonella Typhimurium) and two spoilage bacteria (Serratia marcescens, Pseudomonas alcaligenes), were investigated. The solid agar surface was chosen as a model to mimic the food surface. The UV dose delivered to the samples ranged between 0.75 and 6.75 mJ/cm2. For the application of single-wavelength UV-LEDs, 271 nm UV-LED displayed the highest inactivation efficiency on the tested bacteria. A synergistic effect was observed when E. coli, S. epidermidis, and S. Typhimurium were exposed to irradiation from 288/271 nm UV-LEDs. The synergy ratios ranged from 0.20 to 0.87. No synergy was observed for S. marcescens and P. alcaligenes, or any bacteria tested with 369/288 or 369/271 nm combined modules. Besides, the inactivation efficiencies of continuous and pulsed irradiation against E. coli and S. epidermidis were compared using three modules: 288 nm, 271 nm, and 288/271 nm UV-LEDs. All of the tested UV-LED modules showed comparable inactivation by continuous and pulsed irradiation with various duty cycles under an equivalent UV dose of 6.46 mJ/cm2. Based on the operation-specific microbial inactivation data, this study demonstrated an effective and sustainable method for inactivating foodborne pathogens and offered strategies to enhance disinfection efficiency for system designers and industrial engineers.

An Unsupervised Prediction Model for Salmonella Detection with Hyperspectral Microscopy: A Multi-Year Validation

Hyperspectral microscope images (HMIs) have been previously explored as a tool for the early and rapid detection of common foodborne pathogenic bacteria. A robust unsupervised classification approach to differentiate bacterial species with the potential for single cell sensitivity is needed for real-world application, in order to confirm the identity of pathogenic bacteria isolated from a food product. Here, a one-class soft independent modelling of class analogy (SIMCA) was used to determine if individual cells are Salmonella positive or negative. The model was constructed and validated with a spectral library built over five years, containing 13 Salmonella serotypes and 14 non-Salmonella foodborne pathogens. An image processing method designed to take less than one minute paired with the one-class Salmonella prediction algorithm resulted in an overall classification accuracy of 95.4%, with a Salmonella sensitivity of 0.97, and specificity of 0.92. SIMCA’s prediction accuracy was only achieved after a robust model incorporating multiple serotypes was established. These results demonstrate the potential for HMI as a sensitive and unsupervised presumptive screening method, moving towards the early (&lt;8 h) and rapid (&lt;1 h) identification of Salmonella from food matrices.

Surface chemistry modified upconversion nanoparticles as fluorescent sensor array for discrimination of foodborne pathogenic bacteria

BackgroundThe identification of foodborne pathogenic bacteria types plays a crucial role in food safety and public health. In consideration of long culturing times, tedious operations and the desired specific recognition elements in conventional methods, the alternative fluorescent sensor arrays can offer a high-effective approach in bacterial identification by using multiple cross-reactive receptors. Herein, we achieve this goal by constructing an upconversion fluorescent sensor array based on anti-stokes luminogens featuring a series of functional lanthanide-doped upconversion nanoparticles (UCNPs) with phenylboronic acid, phosphate groups, or imidazole ionic liquid. The prevalent spotlight effect of microorganism and the electrostatic interaction between UCNPs and bacteria endow such sensor array an excellent discrimination property.ResultsSeven common foodborne pathogenic bacteria including two Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) and five Gram-negative bacteria (Escherichia coli, Salmonella, Cronobacter sakazakii, Shigella flexneri and Vibrio parahaemolyticus) are precisely identified with 100% accuracy via linear discriminant analysis (LDA). Furthermore, blends of bacteria have been identified accurately. Bacteria in real samples (tap water, milk and beef) have been effectively discriminated with 92.1% accuracy.ConclusionsCurrent fluorescence sensor array is a powerful tool for high-throughput bacteria identification, which overcomes the time-consuming bacteria culture and heavy dependence of specific recognition elements. The high efficiency of whole bacterial cell detection and the discrimination capability of life and death bacteria can brighten the application of fluorescence sensor array.

Isolation of swine-derived Lactobacillus plantarum and its synergistic antimicrobial and health-promoting properties with ZnO nanoparticles.

The purpose of this study was to isolate Lactobacillus from gastrointestinal tract of healthy postweaning piglets and investigate its synergistic antimicrobial and probiotic effects with ZnO nanoparticles (nZnO). Of the 128 isolates, Lactobacillus plantarum BLPL03 was selected based on its excellent acid and bile salt tolerance properties. Lactobacillus plantarum BLPL03 was sensitive to β-lactams, macrolides, amphenicols and cephalosporins, whereas it displayed the steady resistance to aminoglycosides, tetracyclines, quinolones and peptide antibiotics. In vitro analysis of antibacterial activities showed that L. plantarum BLPL03 inhibited the four common food-borne pathogenic bacteria including Escherichia coli O157:H7 CMCC 44828, Salmonella Typhimurium ATCC 13311, Staphylococcus aureus CMCC 26003 and Listeria monocytogenes CMCC 54007 in synergy with nZnO. Furthermore, the quantitative polymerase chain reaction test demonstrated that the combined administration of L. plantarum BLPL03 fermentation liquor (LFL) and nZnO synergistically elevated the faecal number of Bifidobacterium by 73·19-fold, and reduced the two potential enteropathogenic bacteria Enterobacteriaceae and Clostridium perfringens in mice challenged with Salm. Typhimurium. Finally, dietary supplementation with low dose of nZnO (20mgkg-1 ) when combined with LFL administration enhanced final body weight, fur appearance and average daily gain, and decreased feed conversion ratio and diarrhoea incidence in weaned piglets. The faecal Bifidobacterium and Lactobacillus of piglets were dramatically enhanced by 81·96- and 3·15-fold, respectively, after administration of a mixture of nZnO and LFL. Meanwhile, combination of nZnO with LFL resulted in low levels of Bacteroides, Enterococcus, and Enterobacteriaceae. A combination of nZnO and LFL exhibits potential health-benefit properties for the control of gut microbial composition by their synergistic antimicrobial and probiotic effects. This study may provide a potential nutritional strategy to improve performance and gut health of animals with gut microbiota disorders caused by pathogen infections and weanling, and so on.

Principal component analysis of MALDI-TOF MS of whole-cell foodborne pathogenic bacteria

The rapid and accurate identification of foodborne pathogenic bacteria is of great importance for human health. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) can be used to rapidly and sensitively identify microorganisms but is limited by the expensive protein databases available. In this study, we established a whole-cell method for the identification of foodborne pathogenic bacteria, using MALDI-TOF MS and principal component analysis (PCA), which did not use protein extractions or expensive protein databases. Thirty strains comprising six common foodborne pathogenic bacteria, namely, Shigella flexneri, Escherichia coli, Staphylococcus aureus, Salmonella enteritidis, Pseudomonas aeruginosa, and Listeria monocytogenes were analyzed using MALDI-TOF MS. The culture time, matrix, and spotting method were optimized based on peak intensity and deviation. A PCA was performed to analyze the mass spectrometry results of six samples and proved capable of identifying significant changes in those samples. It was found that directly applying MALDI-TOF MS analysis to whole-cell bacteria, without protein extraction, exhibited rich peak contents and a high level of reproducibility. MALDI-TOF MS combined with PCA is a promising method of rapidly identifying pathogens in food products.

Advances in the detection of virulence genes of Staphylococcus aureus originate from food

Human health is threatened by foodborne illness and Staphylococcus aureus is a common foodborne pathogenic bacteria. It can cause food poisoning when we are infected, therefore, it is necessary to detect pathogenic bacteria. The virulence genes and detection methods of S. aureus are summarized from literatures. Traditional detection methods are simple but need bacteria enrichment and to prolong detection time. Immunological technology has high specificity, but false positive results are easy to occur in its detection. In recent years, molecular biology methods have developed rapidly, and various PCR techniques have been applied to detect foodborne pathogens. Real-time fluorescent quantitative PCR is more effective than ordinary PCR, while price is expensive when use it, the scope of use is limited. LAMP is a flexible detection method, biosensor and flow cytometry are fast but the cost of detection is high and the price is relatively expensive.

The Influence of Heat-Killed Enterococcus faecium BGPAS1-3 on the Tight Junction Protein Expression and Immune Function in Differentiated Caco-2 Cells Infected With Listeria monocytogenes ATCC 19111.

Listeria monocytogenes, the common foodborne pathogenic bacteria species, compromises the intestinal epithelial barrier, leading to development of the listeriosis, a severe disease especially among immunocompromised individuals. L. monocytogenes infection usually requires antibiotic treatment, however, excessive use of antibiotics promotes emergence of antibiotic resistance and the destruction of gut microbiota. Probiotics, including lactic acid bacteria (LAB), have been repeatedly proven as an alternative approach for the treatment of various infections. We have analyzed the potential of Enterococcus faecium BGPAS1-3, a dairy isolate exhibiting strong direct antilisterial effect, to modulate the response of differentiated Caco-2 intestinal epithelial cells to L. monocytogenes ATCC 19111 infection. We showed that the molecule with antilisterial effect is a bacterial cell-wall protein that is highly resistant to the high-temperature treatment. When we tested the antilisterial potential of heat-killed BGPAS1-3, we found that it could prevent tight junction disruption in differentiated Caco-2 monolayer infected with L. monocytogenes ATCC 19111, induce antilisterial host response mechanisms, and stimulate the production of protective TGF-β in intestinal epithelial cells. We also showed that the modulation of MyD88 dependent TLR2 and TLR4 pathways by BGPAS1-3 are involved in host response against L. monocytogenes ATCC 19111. Since heat-killed BGPAS1-3 possess strong antilisterial effects, such postbiotic could be used as a controllable and safe therapeutic.

The fingerprint mapping and genotyping systems application on methicillin-resistant Staphylococcus aureus

As a typical Gram-positive microorganism, S. aureus was recognized as common foodborne pathogenic bacteria in food industry. To study their individuality and pathogenicity mechanism, thirty-three Staphylococci strains were applied to the investigation with the identification of MRSA by PCR targeting on S. aureus specific 16S rRNA and femA genes as well as methicillin-resistant mecA and orfX elements by multiplex-PCR assay. Fingerprinting mapping was then employed using three typing systems (KZ/M13, IS256 and ERIC2) to genotype 33 MRSA strains. As the result indicated, all 33 Staphylococci strains were identified as MRSA. However, diversity occurred among different fingerprinting system results. KZ/M13 system and IS256 system both typed 10 genotypes while ERIC2 system had 8 genotypes. Based on the genotyping results, a discussion was performed in typing ability, discriminatory ability and accordance ratio. Given the above studies, a novel rapid detection method for MRSA was conducted with multiplex-PCR, which possessed rapidity and accuracy. Meanwhile, three fingerprinting systems showed high sensitivity, resolution and classification ratio in MRSA typing. These methods have a broad application prospect in food safety and epidemiology in the future.

Polyphenols from selected dietary spices and medicinal herbs differentially affect common food-borne pathogenic bacteria and lactic acid bacteria

Phenolic rich extracts from edible plants exhibit antimicrobial ability against various pathogens, however, their effects on probiotic bacteria have been much less investigated. This study, therefore, investigated and compared the effects of phenolic rich extracts from six dietary spices and medicinal herbs (Padang cassia, Chinese cassia, oregano, Japanese knotweed, pomegranate peel and clove) on five common food-borne pathogenic bacteria, including Bacillus cereus, Escherichia coli, Salmonella enterica subsp. enterica serovar typhimurium, Shigella flexneri and Staphylococcus aureus, and five selected lactic acid bacteria (LAB), including Lactobacillus (L.) acidophilus, L. delbrueckii subsp. bulgaricus, L. casei, L. plantarum and L. rhamnosus. Antimicrobial tests, included diameter of inhibition zone (DIZ), minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), were performed. Considering the food-borne pathogenic bacteria, the DIZ values ranged from 9.33 to 26 mm, while the DIZ for LAB were overall less than 8 mm. From the results of MIC, Japanese knotweed, pomegranate peel and clove extracts showed stronger inhibitory effects on Shigella flexneri and Staphylococcus aureus, about 313–2500 μg/mL, while the MIC values of phenolic rich extracts on other bacteria, including LAB, were generally more than 2500 μg/mL. Overall, the phenolic rich extracts possessed evident antibacterial ability against food-borne pathogenic bacteria, but not against LAB, suggesting that these phenolic rich extracts did not inhibit the growth of probiotic bacteria. Furthermore, the main phenolic compounds of selected edible plants, including carvacrol, trans-cinnamaldehyde, p-coumaric acid, eugenol, gallic acid and rosmarinic acid, were confirmed to possess strong antibacterial effect against the selected food-borne pathogenic bacteria, suggesting that they were mainly responsible for the antibacterial activity of phenolic rich extracts against pathogenic bacteria. In conclusion, natural phenolic rich extracts exhibit differential effects on food-borne pathogenic bacteria and probiotic LAB, providing a scientific basis for their application in foods not only to extend the shelf-life by controlling bacterial contamination but also to enhance health benefits of foods.

Borago officinalis L. flower: a comprehensive study on bioactive compounds and its health-promoting properties

The herbal plant Borago officinalis L. flower were analysed for its bioactive compounds and antioxidant, antibacterial, anti-inflammatory and anticancer activities using different solvent polarities (methanol, ethanol and water). The RP-HPLC analyses of the methanolic extract confirmed the presence of phenolics (gallic acid, pyrogallol, salicylic acid, caffeic acid), flavonoids (myricetin, rutin) and isoflavonoid (daidzein). Besides, the major individual fatty acids of methanolic extract were α-linolenic, stearidonic, palmitic, linoleic and γ-linolenic acids. The methanolic extract possessed the highest antioxidant properties as compared to the ethanolic and water extracts. The flower methanolic, ethanolic and water extracts showed high, moderate and weak antibacterial activities against common human and foodborne pathogenic bacteria, respectively. Furthermore, the flower extracts showed weak anti-inflammatory in murine RAW 264.7 macrophage cells and low anticancer properties against human hepatic, prostate and colon cancer cells. This high-value flower could be considered as a source of putative antioxidant and antibacterial compounds to improve the human health and to be used as biopreservative in food and cosmetic industries.

Phytochemical evaluation, antioxidant properties and antibacterial activity of Iranian medicinal herb Galanthus transcaucasicus Fomin

This study was performed to determine bioactive compounds such as flavonoid and phenolic contents by HPLC and gas chromatography–mass spectrophotometry (GC–MS) and evaluate their antioxidant and antibacterial activities in bulb, flower and shoot extracts of Galanthus transcaucasicus Fomin. The overall results indicated that shoot part contained higher amounts of phenolics and flavonoids compared to the bulb and flower with respective values of 4.45and 2.67 mg/g DW. Besides, HPLC analyses showed that the gallic acid and syringic acid were the major phenolic contents in bulb, flower and shoot of G. transcaucasicus extracts. Apart from that, naringin was the main flavonoid compounds in bulb, flower and shoot. Volatile metabolites were detected by GC–MS screening that indicated 2-furancarboxaldehyde, 2,3-butanediol, and acetic acid as the main compounds in the bulb, flower and shoot extracts. The results of antioxidant activity test demonstrated that shoot extracts of G. transcaucasicus exhibited higher antioxidant activities compare to bulb and flower. Furthermore, the shoot, flower and bulb extracts showed high, moderate and weak antibacterial activities against common human and food borne pathogenic bacteria, respectively. The overall results revealed that various phytochemicals and bioactive compound in different parts of G. transcaucasicus could be considered as a source of putative antioxidant and antibacterial properties that could be used as biopreservative in food and cosmetic industries.

Application of mixture design to introduce an optimum cell-free supernatant of multiple-strain mixture (MSM) for Lactobacillus against food-borne pathogens

This study aimed to find out an optimum multiple-strain mixture (MSM) of Lactobacillus with the highest antimicrobial activity (AA) against common food-borne pathogenic bacteria (Escherichia coli, Salmonella enteritidis, Listeria monocytogenes, and Bacillus cereus) through mixture design (MD). Hence, Lactobacillus strains were isolated from Iranian traditional fermented olive and pickled garlic, then molecular identified. The results showed that cell-free supernatant (CFS) of the all Lactobacillus isolates had higher AA compared to their microbial suspensions. Therefore, CFS of the Lactobacillus isolates was used to find an optimum proportion through MD. A mixture containing 10% CFS of L. brevis isolated from fermented olive (A*), 80% CFS of L. plantarum isolated from fermented olive (B*), and 10% CFS of L. brevis isolated from pickled garlic (C*) was found as the optimum mixture against common food-borne pathogens. After incubation at 37 °C for 24 h, optical density (OD) of E. coli, S. enteritidis, L. monocytogenes and B. cereus treated with this optimum mixture were 0.131, 0.240, 0.211 and 0.483, respectively.