Cheap extraction of antibacterial compounds of berry pomace and their mode of action against the pathogen Campylobacter jejuni

The antibacterial mechanism of (-)-epigallocatechin-3-gallate (EGCG) against Campylobacter jejuni through transcriptome profiling

(-)-Epigallocatechin-3-gallate (EGCG) has been shown antibacterial activity against Campylobacter jejuni; however, the relevant antibacterial mechanism is unknown. In this study, phenotypic experiments and RNA sequencing were used to explore the antibacterial mechanism. The minimum inhibitory concentration of EGCG on C. jejuni was 32 µg/mL. EGCG-treated was able to increase intracellular reactive oxygen species levels and decline bacterial motility. The morphology and cell membrane of C. jejuni after EGCG treatment were observed collapsed, broken, and agglomerated by field emission scanning electron microscopy and fluorescent microscopy. The RNA-seq analysis presents that there are 36 and 72 differential expressed genes after C. jejuni was treated by EGCG with the concentration of 16 and 32 µg/mL, respectively. EGCG-treated increased the thioredoxin expression, which was a critical protein to resist oxidative stress. Moreover, downregulation of the flgH and flgM gene in flagellin biosynthesis of C. jejuni was able to impair the flagella, reducing cell motility and virulence. The primary antibacterial mechanism revealed by RNA-seq is that EGCG with iron-chelating activity competes with C. jejuni for iron, causing iron deficiency in C. jejuni, which potentially impacts the survival and virulence of C. jejuni. The results suggested a new direction for exploring the activity of EGCG against C. jejuni in the food industry. PRACTICAL APPLICATION: A deeper understanding of the antibacterial mechanism of EGCG against C. jejuni was more beneficial in improving the food safety, eliminating concerns about human health caused by C. jejuni in future food, and promoting the natural antibacterial agent EGCG application in the food industry.

In Vitro Antibacterial and Antioxidative Activity and Polyphenolic Profile of the Extracts of Chokeberry, Blackcurrant, and Rowan Berries and Their Pomaces

The chemical composition of berries and berry pomaces is diverse, containing polyphenolic components that may have both antibacterial and antioxidative properties. In the present study, in vitro antibacterial effect of the extracts of chokeberry, blackcurrant, and rowan berries and berry pomaces against L. monocytogenes, S. aureus, E. coli, and C. jejuni was studied. In addition, the polyphenolic profile and antioxidant activity of these extracts were investigated. The polyphenolic profiles in the aqueous and 30% ethanolic extracts were determined chromatographically by HPLC-MS, and the total polyphenol content was estimated spectrophotometrically by HPLC-DAD-UV. The minimal inhibition concentrations (MICs) of the extracts against tested bacteria were determined by the broth microdilution method. The content of total polyphenols was highest and good antioxidative properties of the extracts were determined for chokeberry and blackcurrant berries and their pomaces. The highest proportions of total quercetin derivatives and anthocyanins were found in the extracts of chokeberry berry/pomace and blackcurrant berry/pomace, respectively. The sensitivity of tested microbes to the extracts of berries and berry pomaces was as follows: S. aureus > L. monocytogenes > E. coli and C. jejuni. In vitro antibacterial activity of tested extracts depended on the extraction solvent, mainly for the ethanolic extracts. Findings suggest that chokeberry and blackcurrant berries and their pomaces can be used as a good source of polyphenols with antioxidative properties, and they also have antibacterial activity against some foodborne pathogenic bacteria. It is important that the valuable compounds are extracted from juice press residues before their disposal.

Natural Antimicrobial Mixtures Disrupt Attachment and Survival of E. coli and C. jejuni to Non-Organic and Organic Surfaces

The contact and adherence of bacteria to various surfaces has significant consequences on biofilm formation through changes in bacterial surface structures or gene expression with potential ramifications on plant and animal health. Therefore, this study aimed to investigate the effect of organic acid-based mixtures (Ac) on the ability Campylobacter jejuni and Escherichia coli to attach and form biofilm on various surfaces, including plastic, chicken carcass skins, straw bedding, and eggshells. Moreover, we aimed to explore the effect of Ac on the expression of E. coli (luxS, fimC, csgD) and C. jejuni (luxS, flaA, flaB) bacterial genes involved in the attachment and biofilm formation via changes in bacterial surface polysaccharidic structures. Our results show that Ac had a significant effect on the expression of these genes in bacteria either attached to these surfaces or in planktonic cells. Moreover, the significant decrease in bacterial adhesion was coupled with structural changes in bacterial surface polysaccharide profiles, impacting their adhesion and biofilm-forming ability. Essentially, our findings accentuate the potential of natural antimicrobials, such as Ac, in reducing bacterial attachment and biofilm formation across various environments, suggesting promising potential applications in sectors like poultry production and healthcare.

Alternative approaches to therapeutics and subtherapeutics for sustainable poultry production

The world population is growing rapidly and thus its demand for food is growing as well. To meet the demand of the ever-increasing number of consumers, the poultry industry and both of its main sectors-conventional and organic/cage-free farming-are expanding in parallel. Due to increasing demand of poultry products and higher mortality rate of chicks (an average 0.3% increase of mortality over last 5 yr), both conventional and organic poultry farming systems struggle with various issues; animal welfare, environmental sustainability, and antibiotic resistance of the prevailing zoonotic/enteric pathogens are common issues for conventional farming whereas slow growth rate, higher costs, inefficient land use, different diseases of the chicken, and cross-contamination with bacterial pathogens into the final products are the major issues for organic poultry farming. On top of these issues, the use of subtherapeutic antibiotics was recently banned in conventional farming systems and by definition the organic farming system cannot use the antibiotics/synthetic chemicals even for therapeutic use. In conventional farming system, use of therapeutic antibiotics may result in residuals antibiotics in the final products. As a result, sustainable alternatives are in demand to mitigate the prevailing issues for both conventional and organic farming. Potential alternatives may include bacteriophages, vaccination, probiotics, plant-derived prebiotics, and synbiotics. These alternatives have beneficial attributes and shortcomings of their use in both conventional and organic poultry production system. In this review, we'll discuss the scope of these potential alternatives as therapeutics and subtherapeutics in sustainable poultry production and ways to improve their efficacy.

Exploring the antimicrobial effects of a phenolic-rich extract from jabuticaba depulping waste against enterotoxigenic Escherichia coli

This study evaluated the effects of a phenolic-rich extract from jabuticaba [Myrciaria jaboticaba (Vell.) Berg] depulping waste (PEJ) on the survival, antibiotic susceptibility, virulence, and cellular functions of various enterotoxigenic Escherichia coli (ETEC) strains. The minimum inhibitory concentration of PEJ against the five tested ETEC strains was 125 mg mL-1. PEJ at 125 and 250 mg mL-1 caused reductions in viable cell counts of ≥ 3 and ≥ 5 log CFU mL-1 in ETEC over 24 h, respectively. PEJ at subinhibitory concentrations (31.25 and 62.5 mg mL-1) reduced the viable cell counts of ETEC when exposed to in vitro gastrointestinal conditions, besides decreasing the biofilm formation, cell surface hydrophobicity, mucin adhesion, and swimming and swarming motility. PEJ (31.25 and 62.5 mg mL-1) increased the susceptibility of the tested ETEC strains to various clinically relevant antibiotics. The exposure to PEJ (62.5 and 125 mg mL-1) impaired the membrane permeability and enzymatic and efflux pump activities in ETEC cells. PEJ effectively reduces survival, increases antibiotic susceptibility, and attenuates virulence in ETEC. These effects could be linked to a PEJ multi-target action disturbing various cellular functions in ETEC cells. PEJ could be a candidate for developing innovative solutions to prevent and treat ETEC infections.

Antibiofilm and Antiquorum Sensing Potential of Lactiplantibacillus plantarum Z057 against Vibrio parahaemolyticus

Vibrio parahaemolyticus is a widespread foodborne pathogen that causes serious seafood-borne gastrointestinal infections. Biofilm and quorum sensing (QS) are critical in regulating these infections. In this study, first, the ability of Lactiplantibacillus plantarum Z057 to compete, exclude, and displace V. parahaemolyticus biofilm was evaluated. Then, the inhibitory effects of L. plantarum Z057 extract (Z057-E) on V. parahaemolyticus biofilm and QS were explored from the aspects of biofilm biomass, metabolic activity, physicochemical properties, extracellular polymer matrix content, QS signal AI-2 activity, biofilm microstructure, and the expression levels of biofilm and QS-related genes. Results showed that L. plantarum Z057 effectively inhibited biofilm formation of V. parahaemolyticus and interfered with the adhesion of V. parahaemolyticus on the carrier surface. In addition, the Z057-E could significantly reduce the biofilm biomass, metabolic activity, hydrophobicity, auto-aggregation ability, swimming and swarming migration diameter, AI-2 activity, extracellular polysaccharide (EPS), and extracellular protein content of V. parahaemolyticus. Fluorescence microscope and scanning electron microscope (SEM) images demonstrated that the Z057-E could efficiently inactivate the living cells, destroy the dense and complete biofilm architectures, and reduce the essential component of the extracellular polymer matrix. Real-time fluorescence quantitative PCR revealed that the Z057-E treatment down-regulated the expression of flagellum synthesis-related genes (flaA, flgM), EPS, and extracellular protein synthesis-related genes (cpsA, cpsQ, cpsR, ompW), QS-related genes (luxS, aphA, opaR), and hemolysin secretion-related genes (toxS, toxR) of V. parahaemolyticus. Thus, our results suggested that L. plantarum Z057 could represent an alternative biocontrol strategy against foodborne pathogens with anti-adhesive, antibiofilm, and antiquorum sensing activities.

Novel Formulation of Bigel-Based Vegetable Oil Spreads Enriched with Lingonberry Pomace

In this study, bigel-based vegetable oil spreads with lingonberry pomace addition were prepared. The impact of gelatin, agar and collagen was examined as structuring agents as was the effect of lecithin concentration (0.5, 1.0, 1.5%). Prepared systems were evaluated by physical and chemical stability and structural and rheological properties. It was found that all bigel formulations were self-standing with no signs of phase separation at ambient temperature immediately after preparation and after two weeks of storage at 4 °C temperature. The lingonberry pomace addition affected grainy structure formation with homogenous and uniform distribution of fiber particles throughout the bigel matrix and it also altered the colour of the bigels toward a purple-red. Texture, rheological properties and colour of the spread formulations were affected by the type of the structuring agent as well as the lecithin concentration. The presence of the lingonberry pomace enhanced the resistance of the bigel samples to the oxidation process and it was confirmed by the DPPH^• inhibition, peroxide value and oxipress test. Overall, the formulated bigel-based spreads could be beneficial and had a potential application as healthier fat spreads and be a source of dietary fibers (11 g of fibre per 100 g of the spread).

Antagonistic Effects of Conjugated Linoleic Acids of Lactobacillus casei against Foodborne Enterohemorrhagic Escherichia coli

ABSTRACT

Probiotics in fermented foods or commercially available supplements benefit the host by providing metabolites and peptides. The production of these metabolites varies with the available substrates or prebiotics present in the system and their concentration. In this study, 0.5% peanut flour (PF) was used to stimulate the growth and production of metabolites of wild-type Lactobacillus casei (LCwt) and compare with an engineered L. casei (LCCLA) capable of converting a higher amount of conjugated linoleic acid (CLA). The total extracellular metabolites present in the cell-free cultural supernatant (CFCS) of LCwt (without peanut), LCwt+PF (with peanut), and LCCLA were collected after 24 and 48 h of incubation, and their antagonistic activities against enterohemorrhagic Escherichia coli (EHEC EDL933) growth and pathogenesis were evaluated. All collected metabolites exhibited varying efficiency in restraining EHEC EDL933 growth, whereas supplementing a low concentration of CLA to the 48-h CFCS from LCwt showed augmented antagonism toward EHEC EDL933. A downregulation of key virulence genes was observed from metabolites collected at the 48-h time point. These observations indicate that the presence of metabolites in CFCSs-including CLA, which is produced by Lactobacillus and was identified by gas chromatography-mass spectrometry-plays a critical role. This study demonstrates the potential applicability of Lactobacillus-originated CLA in the prevention of EHEC EDL933-mediated illnesses.

HIGHLIGHTS

Antimicrobial Activity of Ohelo Berry (Vaccinium calycinum) Juice against Listeria monocytogenes and Its Potential for Milk Preservation

Listeria monocytogenes is a foodborne pathogen and causes illnesses with a high mortality rate in susceptible populations. Several dairy-related outbreaks have been attributed to contamination by L. monocytogenes, which requires antimicrobial interventions to enhance the safety of these products. This study aimed to determine the antimicrobial activity of the ohelo berry (Vaccinium calycinum), a Hawaiian wild relative of cranberry, against L. monocytogenes in culture media and milk products. The effect of ohelo berry juice at its sub-inhibitory concentrations on the physicochemical properties, biofilm formation, and gene expression of L. monocytogenes was also investigated. The minimum inhibitory concentration of ohelo berry juice against L. monocytogenes was 12.5%. The sub-inhibitory concentration of ohelo berry juice (6.25%) significantly increased the auto-aggregation and decreased the hydrophobicity, swimming motility, swarming motility, and biofilm formation capability of L. monocytogenes. The relative expression of genes for motility (flaA), biofilm formation and disinfectant resistance (sigB), invasion (iap), listeriolysin (hly), and phospholipase (plcA) was significantly downregulated in L. monocytogenes treated by the 6.25% juice. L. monocytogenes was significantly inhibited in whole and skim milk supplemented with 50% ohelo berry juice, regardless of the fat content. These findings highlight the potential of ohelo berry as a natural preservative and functional food to prevent L. monocytogenes infection.

Select Phytochemicals Reduce Campylobacter jejuni in Postharvest Poultry and Modulate the Virulence Attributes of C. jejuni

Consumption or handling of poultry and poultry products contaminated with Campylobacter species are a leading cause of foodborne illness in humans. Current strategies employed to reduce Campylobacter in live chickens provide inconsistent results indicating the need for an alternative approach. This study investigated the efficacy of phytochemicals, namely, turmeric, curcumin, allyl sulfide, garlic oil, and ginger oil, to reduce Campylobacter jejuni in postharvest poultry and sought to delineate the underlying mechanisms of action. Two experiments were conducted on the thigh skin of the chicken, and each experiment was repeated twice. Samples were inoculated with 50 μl (∼10⁷ CFU/sample) of C. jejuni strain S-8 and allowed to adhere for 30 min. Skin samples were dipped into their respective prechilled treatment solutions (0.25 and 0.5% in experiments 1 and 2, respectively) at 4°C for an hour to simulate chilling tank treatment, followed by plating to enumerate C. jejuni (n = 3 samples/treatment/trial). The mechanisms of action(s) were investigated using subinhibitory concentration (SIC) in adhesion, quorum sensing, and gene expression analyses. Adhesion assay was conducted on the monolayers of ATCC CRL-1590 chicken embryo cells challenged with C. jejuni and incubated in the presence or absence of phytochemicals for 1.5 h, followed by plating to enumerate adhered C. jejuni. The effects of phytochemicals on quorum sensing and cell viability were investigated using Vibrio harveyi bioluminescence and LIVE/Dead BacLight^TM bacterial viability assays, respectively. In addition, droplet digital PCR determined the gene expression analyses of C. jejuni exposed to phytochemicals. Data were analyzed by GraphPad Prism version 9. C. jejuni counts were reduced by 1.0–1.5 Log CFU/sample with garlic oil or ginger oil at 0.25 and 0.5% (p < 0.05). The selected phytochemicals (except curcumin) reduced the adhesion of C. jejuni to chicken embryo cells (p < 0.05). In addition, all the phytochemicals at SIC reduced quorum sensing of C. jejuni (p < 0.05). The cell viability test revealed that cells treated with 0.25% of phytochemicals had compromised cell membranes indicating this as a mechanism that phytochemicals use to damage/kill C. jejuni. This study supports that the application of phytochemicals in postharvest poultry would significantly reduce C. jejuni in poultry meat.

On the mechanism behind enhanced antibacterial activity of alkyl gallate esters against foodborne pathogens and its application in Chinese icefish preservation

The objective of this study was to investigate antibacterial activities and action mode of alkyl gallates against three food-related bacteria. Results show that the length of the alkyl chain plays a critical role in eliciting their antibacterial activities and octyl gallate (GAC8) exhibited an outstanding bactericidal effect against these strains. A possible bactericidal mechanism of GAC8 against E. coli was fully elucidated by analyzing associated changes in cellular functions of E. coli, including assessments of membrane modification and intracellular oxidation state. Our data strongly suggested that GAC8 functions outside and inside the bacterial membrane and causes increased intracellular reactive oxygen species (hydroxyl radicals) and subsequent oxidative damage. We demonstrated that the hydroxyl radical formation induced by GAC8 is the end product of an oxidative damage cellular death pathway involving a transient depletion of NADH, the tricarboxylic acid cycle, intrinsic redox cycling activities, and stimulation of the Fenton reaction. Also, chitosan-based edible films containing GAC8 have unique superiorities for icefish preservation at 4 °C. This research highlights the effectiveness of GAC8 as an attractive antibacterial, which possesses both antioxidant and antibacterial activities and can be used as a multifunctional food additive combined with the benefit of active packaging for food preservations.

Approaches to prevent and control Campylobacter spp. colonization in broiler chickens: a review

Campylobacter, Gram-negative bacteria, is the most common cause of acute bacterial enteritis in human beings, both in developing and developed countries. It is believed that poultry, in particular broiler chickens, is the main host of human infection with Campylobacter. Handling and consumption of contaminated chicken meat are the usual modes of transmission. Prevention and reduction of Campylobacter colonization in poultry farms will cut off the road of infection transmission to humans throughout the food chain. With the incidence of antibiotic resistance and with growing concern about superbugs, the search for natural and safe alternatives will considerably increase in the coming years. In this review, we will discuss the prevalence and risk factors of Campylobacter colonization in broiler chickens and sources of infection. This review also provides extensive and recent approaches to prevent and control Campylobacter colonization in broiler chickens, including biosecurity measures, natural feed/drinking water additives with antimicrobial properties, bacteriocins, bacteriophages, antimicrobial peptides, and vaccination strategies to prevent and control the incidence of human campylobacteriosis.

Controlled-release casein/cinnamon essential oil nanospheres for the inactivation of Campylobacter jejuni in duck

Campylobacter jejuni (C. jejuni) is one of the most common foodborne pathogens that cause human sickness mostly through the poultry food chain. Cinnamon essential oil (CEO) has excellent antibacterial ability against C. jejuni growth. This study investigated the antibacterial mechanism of CEO against C. jejuni primarily through metabolism, energy metabolism of essential enzymes (AKPase, β-galactosidase, and ATPase), and respiration metabolism. Results showed that the hexose monophosphate pathway (HMP) was inhibited, and that the enzyme activity of G₆DPH substantially decreased upon treatment with CEO. Analysis of the effect of CEO on the expression of toxic genes was performed by the real-time PCR (RT-PCR). The expression levels of the toxic genes cadF, ciaB, fliA, and racR under CEO treatment were determined. Casein/CEO nanospheres were further prepared for the effective inhibition of C. jejuni and characterized by particle-size distribution, zeta-potential distribution, fluorescence, TEM, and GC-MS methods. Finally, the efficiency of CEO and casein/CEO nanospheres in terms of antibacterial activity against C. jejuni was verified. The casein/CEO nanospheres displayed high antibacterial activity on duck samples. The population of the test group decreased from 4.30 logCFU/g to 0.86 logCFU/g and 4.30 logCFU/g to 2.46 logCFU/g at 4 °C and at 25 °C for C. jejuni, respectively. Sensory evaluation and texture analysis were also conducted on various duck samples.

Antimicrobial and Antivirulence Impacts of Phenolics on Salmonella Enterica Serovar Typhimurium

Salmonella enterica serovar Typhimurium (ST) remains a major infectious agent in the USA, with an increasing antibiotic resistance pattern, which requires the development of novel antimicrobials capable of controlling ST. Polyphenolic compounds found in plant extracts are strong candidates as alternative antimicrobials, particularly phenolic acids such as gallic acid (GA), protocatechuic acid (PA) and vanillic acid (VA). This study evaluates the effectiveness of these compounds in inhibiting ST growth while determining changes to the outer membrane through fluorescent dye uptake and scanning electron microscopy (SEM), in addition to measuring alterations to virulence genes with qRT-PCR. Results showed antimicrobial potential for all compounds, significantly inhibiting the detectable growth of ST. Fluorescent spectrophotometry and microscopy detected an increase in relative fluorescent intensity (RFI) and red-colored bacteria over time, suggesting membrane permeabilization. SEM revealed severe morphological defects at the polar ends of bacteria treated with GA and PA, while VA-treated bacteria were found to be mid-division. Relative gene expression showed significant downregulation in master regulator hilA and invH after GA and PA treatments, while fliC was upregulated in VA. Results suggest that GA, PA and VA have antimicrobial potential that warrants further research into their mechanism of action and the interactions that lead to ST death.

Competitive reduction of poultry-borne enteric bacterial pathogens in chicken gut with bioactive Lactobacillus casei

In this study, the effect of sustainable probiotics on Campylobacter jejuni colonization and gut microbiome composition was evaluated using chicken as a model organism. Chickens were given Lactobacillus casei over-expressing myosin-cross-reactive antigen (LC+mcra). LC+mcra can generate bioactive compounds in larger quantity including conjugated linoleic acid. A total of 120 chickens were used in duplicate trials to investigate the effectiveness of LC+mcra in decreasing C. jejuni colonization by means of kanamycin resistant strain compared to the control group. We observed that LC+mcra can efficiently colonize various parts of the chicken gut and competitively reduce colonization of natural and challenged C. jejuni and natural Salmonella enterica. LC+mcra was found to reduce C. jejuni colonization in cecum, ileum and jejunum, by more than one log CFU/g when compared to the no-probiotic control group. Furthermore, 16S rRNA compositional analysis revealed lower abundance of Proteobacteria, higher abundance of Firmicutes, along with enriched bacterial genus diversity in gut of LC+mcra fed chicken. Decreased contamination of drinking water by C. jejuni and S. enterica was also observed, suggesting a potential function of reducing horizontal transfer of enteric bacteria in poultry. Outcomes of this study reveal high potential of LC+mcra as sustainable approach to decrease colonization of C. jejuni and S. enterica in poultry gut along with other beneficial attributes.

Growth Inhibition and Alternation of Virulence Genes of Salmonella on Produce Products Treated with Polyphenolic Extracts from Berry Pomace

ABSTRACT

Organic farming, including integrated crop-livestock farms and backyard farming, is gaining popularity in the United States, and products from these farms are commonly sold at farmers' markets, local stores, and roadside stalls. Because organic farms avoid using antibiotics and chemicals and because they use composted animal waste and nonprofessional harvesting and packaging methods, their products have an increased risk of cross-contamination with zoonotic pathogens. This study sets out to evaluate the efficiency of new postharvest disinfection processes using natural berry pomace extracts (BPEs) as a means to reduce the bacterial load found in two common leafy greens, spinach and celery. Spinach and celery were inoculated with a fixed bacterial load of Salmonella Typhimurium and later were soaked in BPE-supplemented water (wBPE) for increasing periods of time, at two different temperatures (24 and 4°C). The remaining live bacteria were quantified (log CFU per leaf), and numbers were compared with those on vegetables soaked in water alone. The relative expression of virulence genes (hilA1/C1/D1, invA1/C1/E1/F1) of wBPE-treated Salmonella Typhimurium was determined. For spinach, there was a significant (P < 0.05) reduction of Salmonella Typhimurium: 0.2 to 1.2 log CFU/mL and 0.5 to 5 log CFU/mL at 24 and 4°C, respectively. For celery, there was also a significant (P < 0.05) reduction of Salmonella Typhimurium at either 24 or 4°C. The changes in relative expression of virulence genes of Salmonella Typhimurium isolated from spinach and celery varied depending on the treatment conditions but showed a significant down-regulation of inv genes when treated at 24°C for 1,440 min (P < 0.05). After seven uses, the total polyphenolic compounds in wBPE remained at an effective concentration. This research suggests that soaking these vegetables with BPE-containing water at lower temperatures can still reduce the Salmonella Typhimurium load enough to minimize the risk of infection and alter virulence properties.

HIGHLIGHTS

Carvacrol attenuates Campylobacter jejuni colonization factors and proteome critical for persistence in the chicken gut

Campylobacter jejuni is a major foodborne pathogen that causes gastroenteritis in humans. Chickens act as the reservoir host for C. jejuni, wherein the pathogen asymptomatically colonizes the ceca leading to contamination of carcasses during slaughter. The major colonization factors in C. jejuni include motility, intestinal epithelial attachment, acid/bile tolerance, and quorum sensing. Reducing the expression of the aforementioned factors could potentially reduce C. jejuni colonization in chickens. This study investigated the efficacy of subinhibitory concentration (SIC; compound concentration not inhibiting bacterial growth) of carvacrol in reducing the expression of C. jejuni colonization factors in vitro. Moreover, the effect of carvacrol on the expression of C. jejuni proteome was investigated using liquid chromatography-tandem mass spectrometry. The motility assay was conducted at 42°C, and the motility zone was measured after 24 h of incubation. For the adhesion assay, monolayers of primary chicken enterocytes (∼10⁵ cells/well) were inoculated with C. jejuni (6 log cfu/well) either in the presence or absence of carvacrol, and the adhered C. jejuni were enumerated after 90 min of incubation at 42°C. The effect of carvacrol on C. jejuni quorum sensing and susceptibility to acid/bile stress was investigated using a bioluminescence assay and an acid–bile survival assay, respectively. The SIC (0.002%) of carvacrol reduced the motility of C. jejuni strains S-8 and NCTC 81-176 by ∼50 and 35%, respectively (P < 0.05). Carvacrol inhibited C. jejuni S-8 and NCTC 81-176 adhesion to chicken enterocytes by ∼0.8 and 1.5 log cfu/mL, respectively (P < 0.05). Moreover, carvacrol reduced autoinducer-2 activity and increased the susceptibility of C. jejuni to acid and bile in both the strains (P < 0.05). Liquid chromatography-tandem mass spectrometry revealed that the SIC of carvacrol reduced the expression of selected C. jejuni colonization proteins critical for motility (methyl-accepting chemotaxis protein), adhesion (GroL), growth and metabolism (AspA, AcnB, Icd, Fba, Ppa, AnsA, Ldh, Eno, PurB-1), and anaerobic respiration (NapB, HydB, SdhA, NrfA) (P < 0.05). Results suggest the mechanisms by which carvacrol could reduce C. jejuni colonization in chickens.

Effectiveness of probiotics, prebiotics, and prebiotic-like components in common functional foods

The bioactive ingredients in commonly consumed foods include, but are not limited to, prebiotics, prebiotic-like components, probiotics, and postbiotics. The bioactive ingredients in functional foods have also been associated with beneficial effects on human health. For example, they aid in shaping of gut microflora and promotion of immunity. These functional components also contribute in preventing serious diseases such as cardiovascular malfunction and tumorigenesis. However, the specific mechanisms of these positive influences on human health are still under investigation. In this review, we aim to emphasize the major contents of probiotics, prebiotics, and prebiotic-like components commonly found in consumable functional foods, and we present an overview of direct and indirect benefits they provide on human health. The major contributors are certain families of metabolites, specifically short-chain fatty acids and polyunsaturated fatty acids produced by probiotics, and prebiotics, or prebiotic-like components such as flavonoids, polyphenols, and vitamins that are found in functional foods. These functional ingredients in foods influence the gut microbiota by stimulating the growth of beneficial microbes and the production of beneficial metabolites that, in turn, have direct benefits to the host, while also providing protection from pathogens and maintaining a balanced gut ecosystem. The complex interactions that arise among functional food ingredients, human physiology, the gut microbiota, and their respective metabolic pathways have been found to minimize several factors that contribute to the incidence of chronic disease, such as inflammation oxidative stress.

Limiting the pathogenesis of Salmonella Typhimurium with berry phenolic extracts and linoleic acid overproducing Lactobacillus casei

The growing threat of emergent multidrug-resistant enteric bacterial pathogens, and their adopted virulence properties are directing to find alternative antimicrobials and/or development of dietaries that can improve host gut health and/or defense. Recently, we found that modified Lactobacillus casei (Lc + CLA) with increased production of conjugated linoleic acid has antimicrobial and other beneficial properties. Further, prebiotic alike products such as berry pomace extracts (BPEs), increase the growth of probiotics and inhibit the growth of certain bacterial pathogens. In this study, we evaluated the antibacterial effect of genetically modified Lc + CLA along with BPEs against major enteric pathogen Salmonella enterica serovar Typhimurium (ST). In mixed culture condition, the growth of ST was significantly reduced in the presence of Lc + CLA and/or BPEs. Bacterial cell-free cultural supernatant (CFCS) collected from wild-type Lc or modified Lc + CLA strains also inhibited the growth and survival of ST, and those inhibitory effects were enhanced in the presence of BPEs. We also found that the interaction of the pathogen with cultured host (HD-11 and INT-407) cells were also altered in the presence of either Lc or Lc + CLA strain or their CFCSs significantly. Furthermore, the relative expression of genes related to ST virulence and physicochemical properties of ST was altered by the effect of CFCSs of either Lc or Lc + CLA. These findings indicate that a diet containing synbiotic, specifically linoleic acid, over-produced Lc + CLA and prebiotic product BPEs, might have the potential to be effective in controlling ST growth and pathogenesis.

Plant Phenolics and Phenolic-Enriched Extracts as Antimicrobial Agents against Food-Contaminating Microorganisms

Phenolic compounds and extracts with bioactive properties can be obtained from many kinds of plant materials. These natural substances have gained attention in the food research as possible growth inhibitors of foodborne pathogenic and spoilage bacteria. Many phenolic-enriched plant extracts and individual phenolics have promising anti-quorum sensing potential as well and can suppress the biofilm formation and toxin production of food-related pathogens. Various studies have shown that plant phenolics can substitute or support the activity of synthetic food preservatives and disinfectants, which, by the way, can provoke serious concerns in consumers. In this review, we will provide a brief insight into the bioactive properties, i.e., the antimicrobial, anti-quorum sensing, anti-biofilm and anti-enterotoxin activities, of plant phenolic extracts and compounds, with special attention to pathogen microorganisms that have food relation. Carbohydrase aided applications to improve the antimicrobial properties of phenolic extracts are also discussed.

Investigating the antimicrobial and antibiofilm effects of cinnamaldehyde against Campylobacter spp. using cell surface characteristics

Campylobacter species are known as biofilm-forming bacteria in food systems. The aim of this study was to evaluate the antimicrobial and antibiofilm effects of cinnamaldehyde against Campylobacter jejuni and Campylobacter coli isolated from chicken meat. The biofilm-forming C. jejuni and C. coli strains from chicken meat were investigated using minimum inhibitory concentration (MIC) and Campylobacter spp. characteristics. The MIC value was 31.25 µg/mL for the Campylobacter strains tested. Cinnamaldehyde had an inhibition and degradation effect on Campylobacter biofilms at concentrations > 15.63 µg/mL. Campylobacter strains treated with 15.63 µg/mL CA exhibited significantly decreased autoaggregation, motility, exopolysaccharide production, and soluble protein. In addition, Campylobacter biofilms formed on stainless steel were degraded following cinnamaldehyde treatment, as determined by scanning electron microscopy. Taken together, these results suggest that cinnamaldehyde constitutes a potential natural preservative against Campylobacter and a nontoxic biofilm remover that could be applied to control food poisoning in the poultry manufacturing-related food industry. PRACTICAL APPLICATION: Cinnamaldehyde was able to effectively remove the biofilm of Campylobacter in the small crack of stainless steel. Cinnamaldehyde has a potential to replace the synthetic antimicrobial and/or antibiofilm agent as well as has a positive influence on consumer concern for the food safety issues of the poultry industries.

Synbiotic-like effect of linoleic acid overproducing Lactobacillus casei with berry phenolic extracts against pathogenesis of enterohemorrhagic Escherichia coli

Background

Majority of enteric infections are foodborne and antimicrobials including antibiotics have been used for their control and treatment. However, probiotics or prebiotics or their combination offer a potential alternative intervention strategy for improving the host health and preventing foodborne pathogen colonization/infections in reservoir. Further, bioengineered probiotics expressing bioactive products to achieve specific function is highly desirable. Recently, we over-expressed mcra (myosin cross-reactive antigen) gene in Lactobacillus casei (Lc) and developed a bioengineered probiotics Lc + CLA which produce higher amounts of metabolites including conjugated linoleic acid (CLA). Furthermore, we also reported that prebiotic like components such as berry pomace (byproduct) phenolic extracts (BPEs) can enhance the growth of probiotics and improved the beneficial effects of probiotics. In this study, we evaluated the antimicrobial effect of modified Lc + CLA in combination of BPEs on growth, survival and pathogenesis of enterohemorrhagic Escherichia coli (EHEC).

Results

In mixed culture condition, the growth of EHEC was significantly reduced in the presence Lc + CLA and/or BPEs. Cell-free cultural supernatant (CFCS) collected from Lc or Lc + CLA strain also inhibited the growth and survival of EHEC and the inhibitory effects of CFCSs against EHEC were enhanced in the presence of BPEs in concentration dependent manner. Interaction between EHEC and intestinal epithelial INT-407 cells were also altered significantly in the presence of either Lc or Lc + CLA strain or their CFCSs with or without BPEs. The expression of multiple virulence genes and physicochemical properties of EHEC were also altered when the bacterial cells were pretreated with CFCSs and/or BPEs.

Conclusions

These results showed that diet containing bioactive Lc + CLA and natural prebiotic like component such as BPEs might be an effective way to prevent foodborne infections with EHEC.

Effect of conjugated linoleic acid overproducing Lactobacillus with berry pomace phenolic extracts on Campylobacter jejuni pathogenesis

Campylobacter jejuni (CJ) is one of the predominant causative agents of acute gastroenteritis in the US and other developed countries through the handling of raw chicken or the consumption of undercooked poultry and poultry products. Probiotics and their metabolites such as conjugated linoleic acids (CLAs) play a crucial role in improving host health and act as antimicrobials against enteric pathogens. Furthermore, prebiotics or prebiotic-like components such as bioactive phenolics from berry pomace can stimulate the growth of beneficial microbes including Lactobacillus casei (LC) and its metabolites, and competitively inhibit the growth of enteric bacterial pathogens. In this study, we aimed at enhancing the efficiency of antimicrobial/beneficial activities of LC and the extent of production of bioactive compounds by combining berry pomace phenolic extract (BPPE) and overproducing CLA in L. casei (LC-CLA). Under mixed culture conditions, LC-CLA in the presence of BPPE reduced the growth of CJ by more than 3 log CFU ml-1 within 48 h. The cell-free culture supernatant (CFCS) of LC-CLA in the presence of BPPE also reduced significantly the growth of CJ >3.2 log CFU ml-1 at 24 h. The interactions of CJ with cultured chicken fibroblast cells (DF-1), chicken macrophage (HD-11), and human epithelial cells (HeLa) were altered significantly. Treatments with BPPE and/or CFCS also altered the injured cell number, auto-aggregation capacity and cell surface hydrophobicity of CJ, significantly. Furthermore, combined treatments with BPPE and CFCSs of LC-CLA altered the expression of multiple virulence genes such as ciaB, cdtB, cadF, flaA, and flaB of CJ from 0.45 fold to 6.85 fold. Overall, BPPE enhanced the effect of LC-CLA in the reduction of CJ growth, survival ability, host cell-CJ interactions, and virulence gene expression. This finding indicates that a combination of BPPE and LC-CLA may be able to prevent the colonization of CJ in poultry, reduce the cross-contamination of poultry products and control poultry-borne campylobacteriosis in humans.

Energy Regulated Nutritive and Antioxidant Properties during the Germination and Sprouting of Broccoli Sprouts ( Brassica oleracea var. italica)

The role of energy status in germination and sprouting of broccoli seeds was investigated by exogenous ATP and DNP treatments. With the synthesis of adenylates from 38.82 to 142.69 mg·100 g^-1 DW, the nutritive components (soluble sugar, proteins, pigments, and phenolics) and AAs were increased during germination and early sprouting (day 5). Elements of the BoSnRK2 pathway were down-regulated by more than 2 fold under the energy charge feedback inhibition. At the end of sprouting (day 7), energy depletion resulted in slowdown or reduced nutritional accumulation and antioxidant capacities. Exogenous ATP depressed the BoSnRK2 pathway by maintaining the energy status at high levels and further promoted the nutrition and antioxidant levels. It also prevented the energy depletion at day 7. On the contrary, DNP reduced the ATP contents (16.10-26.86%) and activated the BoSnRK2 pathway. It also notably suppressed the energy-consuming activities including germination, sprouts growth, and secondary metabolic synthesis.

Alternative Growth Promoters Modulate Broiler Gut Microbiome and Enhance Body Weight Gain

Antibiotic growth promoters (AGPs) are frequently used to enhance weight-gain in poultry production. However, there has been increasing concern over the impact of AGP on the emergence of antibiotic resistance in zoonotic bacterial pathogens in the microbial community of the poultry gut. In this study, we adopted mass-spectrophotometric, phylogenetic, and shotgun-metagenomic approaches to evaluate bioactive phenolic extracts (BPE) from blueberry (Vaccinium corymbosum) and blackberry (Rubus fruticosus) pomaces as AGP alternatives in broilers. We conducted two trials with 100 Cobb-500 broiler chicks (in each trial) in four equal groups that were provided water with no supplementation, supplemented with AGP (tylosin, neomycin sulfate, bacitracin, erythromycin, and oxytetracycline), or supplemented with 0.1 g Gallic acid equivalent (GAE)/L or 1.0 g GAE/L (during the last 72 h before euthanasia) of BPE for 6 weeks. When compared with the control group (water only), the chickens supplemented with AGP and 0.1 g GAE/L of BPE gained 9.5 and 5.8% more body weight, respectively. The microbiomes of both the AGP- and BPE-treated chickens had higher Firmicutes to Bacteroidetes ratios. AGP supplementation appeared to be associated with higher relative abundance of bacteriophages and unique cecal resistomes compared with BPE supplementation or control. Functional characterization of cecal microbiomes revealed significant animal-to-animal variation in the relative abundance of genes involved in energy and carbohydrate metabolism. These findings established a baseline upon which mechanisms of plant-based performance enhancers in regulation of animal growth can be investigated. In addition, the data will aid in designing alternate strategies to improve animal growth performance and consequently production.

Application of β-Resorcylic Acid as Potential Antimicrobial Feed Additive to Reduce Campylobacter Colonization in Broiler Chickens

Campylobacter is one of the major foodborne pathogens that result in severe gastroenteritis in humans, primarily through consumption of contaminated poultry products. Chickens are the reservoir host of Campylobacter, where the pathogen colonizes the ceca, thereby leading to contamination of carcass during slaughter. A reduction in cecal colonization by Campylobacter would directly translate into reduced product contamination and risk of human infections. With increasing consumer demand for antibiotic free chickens, significant research is being conducted to discover natural, safe and economical antimicrobials that can effectively control Campylobacter colonization in birds. This study investigated the efficacy of in-feed supplementation of a phytophenolic compound, β-resorcylic acid (BR) for reducing Campylobacter colonization in broiler chickens. In two separate, replicate trials, day-old-chicks (Cobb500; n = 10 birds/treatment) were fed with BR (0, 0.25, 0.5, or 1%) in feed for a period of 14 days (n = 40/trial). Birds were challenged with a four-strain mixture of Campylobacter jejuni (∼10⁶ CFU/ml; 250 μl/bird) on day 7 and cecal samples were collected on day 14 for enumerating surviving Campylobacter in cecal contents. In addition, the effect of BR on the critical colonization factors of Campylobacter (motility, epithelial cell attachment) was studied using phenotypic assay, cell culture, and real-time quantitative PCR. Supplementation of BR in poultry feed for 14 days at 0.5 and 1% reduced Campylobacter populations in cecal contents by ∼2.5 and 1.7 Log CFU/g, respectively (P < 0.05). No significant differences in feed intake and body weight gain were observed between control and treatment birds fed the compound (P > 0.05). Follow up mechanistic analysis revealed that sub-inhibitory concentration of BR significantly reduced Campylobacter motility, attachment to and invasion of Caco-2 cells. In addition, the expression of C. jejuni genes coding for motility (motA, motB, fliA) and attachment (jlpA, ciaB) was down-regulated as compared to controls (P < 0.05). These results suggest that BR could potentially be used as a feed additive to reduce Campylobacter colonization in broilers.

Eradication and Sensitization of Methicillin Resistant Staphylococcus aureus to Methicillin with Bioactive Extracts of Berry Pomace

The therapeutic roles of phenolic blueberry (Vaccinium corymbosum) and blackberry (Rubus fruticosus) pomace (commercial byproduct) extracts (BPE) and their mechanism of actions were evaluated against methicillin resistant Staphylococcus aureus (MRSA). Five major phenolic acids of BPE, e.g., protocatechuic, p. coumaric, vanillic, caffeic, and gallic acids, as well as crude BPE completely inhibited the growth of vegetative MRSA in vitro while BPE+methicillin significantly reduced MRSA biofilm formation on plastic surface. In addition, BPE restored the effectiveness of methicillin against MRSA by down-regulating the expression of methicillin resistance (mecA) and efflux pump (norA, norB, norC, mdeA, sdrM, and sepA) genes. Antibiogram with broth microdilution method showed that MIC of methicillin reduced from 512 μg/mL to 4 μg/mL when combined with only 200 μg Gallic Acid Equivalent (GAE)/mL of BPE. Significant reduction in MRSA adherence to and invasion into human skin keratinocyte Hek001 cells were also noticed in the presence of BPE. BPE induced anti-apoptosis and anti-autophagy pathways through overexpression of Bcl-2 gene and down-regulation of TRADD and Bax genes (inducers of apoptosis pathway) in Hek001 cells. In summary, novel and sustainable prophylactic therapy can be developed with BPE in combination with currently available antibiotics, especially methicillin, against skin and soft tissue infections with MRSA.

Combined treatments of chestnut shell extract, fumaric acid, and mild heat to inactivate foodborne pathogens inoculated on beetroot (Beta vulgaris L.) leaves

To evaluate the combined treatments of chestnut shell extract (CSE), fumaric acid (FA), and mild heat (MH) on the inactivation of Escherichia coli O157:H7 and Listeria monocytogenes inoculated on beetroot leaves, samples were treated with different concentrations of CSE or FA, as well as combinations of 0.5% CSE/0.5% FA and 0.5% CSE/MH at 50°C/0.5% FA. Among the treatments, the combined treatment of CSE/MH/FA was most effective, reducing the populations of E. coli O157:H7 and L. monocytogenes on beetroot leaves by 3.18 and 3.76 log CFU/g, respectively. In addition, the initial populations of pre-existing bacteria on beetroot leaves were reduced by 2.58 log CFU/g after the combined treatment. The inactivation effect was retained during storage at 4°C for 8 days. These results indicate that the combined treatment of CSE, FA, and MH can be effective in decontamination from foodborne pathogens and improving in the microbial safety of beetroot leaves during storage.