Effect of Lacticaseibacillus casei LC2W Supplementation on Glucose Metabolism and Gut Microbiota in Subjects at High Risk of Metabolic Syndrome: A Randomized, Double-blinded, Placebo-controlled Clinical Trial

Metabolic syndrome (MetS) is a global epidemic complex and will cause serious metabolic comorbidities without treatment. A prevention strategy for MetS development has been proposed to modulate gut microbiota by probiotic administration to improve intestinal dysbiosis and benefit the host. Lacticaseibacillus casei LC2W has exhibited positive effects in preventing colitis and anti-hypertension in vivo. However, the effect of L. casei LC2W on subjects at high risk of MetS is unknown. Here, a randomized, double-blinded, placebo-controlled study was conducted on 60 subjects with high risk of MetS, and the hypoglycemic and hypolipidemic activity and possible pathways of L. casei LC2W were inferred from the correlation analysis with gut microbiome composition, function, and clinical phenotypic indicators. The results showed that oral administration of L. casei LC2W could exert significant benefits on weight control, glucose and lipid metabolism, inflammatory and oxidative stress parameters, and SCFA production, as well as modulate the composition of gut microbiota. The relative abundance of Lacticaseibacillus, Bifidobacterium, Dorea, and Blautia was enriched, and their interaction with other gut microbes was strengthened by oral administration of L. casei LC2W, which was beneficial in ameliorating gut inflammation, promoting glucose and lipids degradation pathways, thus alleviated MetS. The present study confirmed the prevention effects of L. casei LC2W towards MetS from aspects of clinical outcomes and microflora modulation, providing an alternative strategy for people at high risk of MetS.Trial registration: The study was proactively registered in ClinicalTrial.gov with the registration number of ChiCTR2000031833 on April 09, 2020.

Bifidobacterium longum K5 Prevents Enterohaemorrhagic Escherichia coli O157:H7 Infection in Mice through the Modulation of the Gut Microbiota

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 is a commonly encountered foodborne pathogen that can cause hemorrhagic enteritis and lead to hemolytic uremic syndrome (HUS) in severe cases. Bifidobacterium is a beneficial bacterium that naturally exists in the human gut and plays a vital role in maintaining a healthy balance in the gut microbiota. This study investigated the protective effects of B. longum K5 in a mouse model of EHEC O157:H7 infection. The results indicated that pretreatment with B. longum K5 mitigated the clinical symptoms of EHEC O157:H7 infection and attenuated the increase in myeloperoxidase (MPO) activity in the colon of the mice. In comparison to the model group, elevated serum D-lactic acid concentrations and diamine oxidase (DAO) levels were prevented in the K5-EHEC group of mice. The reduced mRNA expression of tight junction proteins (ZO-1, Occludin, and Claudin-1) and mucin MUC2, as well as the elevated expression of virulence factors Stx1A and Stx2A, was alleviated in the colon of both the K5-PBS and K5-EHEC groups. Additionally, the increase in the inflammatory cytokine levels of TNF-α and IL-1β was inhibited and the production of IL-4 and IL-10 was promoted in the K5-EHEC group compared with the model group. B. longum K5 significantly prevented the reduction in the abundance and diversity of mouse gut microorganisms induced by EHEC O157:H7 infection, including blocking the decrease in the relative abundance of Roseburia, Lactobacillus, and Oscillibacter. Meanwhile, the intervention with B. longum K5 promoted the production of acetic acid and butyric acid in the gut. This study provides insights into the use of B. longum K5 for developing probiotic formulations to prevent intestinal diseases caused by pathogenic bacterial infections.

Structures, physical properties and antibacterial activity of silver nanoparticles of Lactiplantibacillus plantarum exopolysaccharide

Lactic acid bacteria (LAB) exopolysaccharide (EPS) has good water absorption, high viscosity, good stability, so it was widely used in probiotics fields. In this study, EPS-producing LAB strain Lactiplantibacillus plantarum HDL-03 was isolated and identified. Moreover, the HDL-03 EPS was used as a stabilizer and mixed with AgNO3 to synthesize a novel nanoparticle AgNPs whose structure and properties were explored. The monosaccharide composition and molecular weight indicated that HDL-03 EPS was a heteropolysaccharide composed of mannose and glucose. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy analysis and methylation results jointly proved it was a heteropolysaccharide containing 1,3-Manp and 1,6-Glcp. The X-Ray diffraction (XRD) results showed that this EPS has an amorphous structure, while the synthesized AgNPs have crystalline properties. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated EPS had a smooth and dense sheet structure, while the surface of AgNPs became rougher and large holes appeared after synthesis. Zeta particle size analysis suggested that the particle size of AgNPs increased by 36.63 nm compared to HDL-03 EPS. FT-IR analysis exhibited that the position of the characteristic peaks of AgNPs changed. The OH moving from a wavelength of 3388.49 cm-1 to a wavelength of 3316.79 cm-1 and telescopic vibration peak changed from 1356.07 cm-1 to 1344.22 cm-1. A plate inhibition test revealed the effect of different concentrations of EPS and AgNO3 synthesized AgNPs on the diameter of inhibition circle produced by the indicator bacteria Escherichia coli and Staphylococcus aureus. Furthermore, AgNPs were applied to the indicator bacteria, which the minimum inhibitory concentration (MIC), time-inhibitory curve, and changes in extracellular conductivity, nucleic acids, proteins, ATP, and lactate dehydrogenase (LDH) levels were determined. The AgNPs inhibited the growth of E. coli and S. aureus and exhibited outstanding antimicrobial properties. With the increase of treatment time, the degree of cell membrane damage increased, the permeability enhanced, and the intracellular substances leaked. These results indicate that HDL-03 EPS has good potential for applications in the production of food packaging, antimicrobials, catheters, textiles and coatings.

Advances in Bio-Optical Imaging Systems for Spatiotemporal Monitoring of Intestinal Bacteria

Vast and complex intestinal communities are regulated and balanced through interactions with their host organisms, and disruption of gut microbial balance can cause a variety of diseases. Studying the mechanisms of pathogenic intestinal flora in the host and early detection of bacterial translocation and colonization can guide clinical diagnosis, provide targeted treatments, and improve patient prognosis. The use of in vivo imaging techniques to track microorganisms in the intestine, and study structural and functional changes of both cells and proteins, may clarify the governing equilibrium between the flora and host. Despite the recent rapid development of in vivo imaging of intestinal microecology, determining the ideal methodology for clinical use remains a challenge. Advances in optics, computer technology, and molecular biology promise to expand the horizons of research and development, thereby providing exciting opportunities to study the spatio-temporal dynamics of gut microbiota and the origins of disease. Here, this study reviews the characteristics and problems associated with optical imaging techniques, including bioluminescence, conventional fluorescence, novel metabolic labeling methods, nanomaterials, intelligently activated imaging agents, and photoacoustic (PA) imaging. It hopes to provide a valuable theoretical basis for future bio-intelligent imaging of intestinal bacteria.

In Vivo Functional Properties of Dairy Bacteria

This literature review aimed to collect investigations on the in vivo evidence for bacteria associated with fermented dairy foods to behave as probiotics with beneficial effects in the prevention and treatment of various diseases. All main bacterial groups commonly present in high numbers in fermented milks or cheeses were taken into account, namely starter lactic acid bacteria (SLAB) Lactobacillus delbrueckii subsp. bulgaricus and lactis, L. helveticus, Lactococcus lactis, Streptococcus thermophilus, non-starter LAB (NSLAB) Lacticaseibacillus spp., Lactiplantibacillus plantarum, dairy propionibacteria, and other less frequently encountered species. Only studies regarding strains of proven dairy origin were considered. Studies in animal models and clinical studies showed that dairy bacteria ameliorate symptoms of inflammatory bowel disease (IBD), mucositis, metabolic syndrome, aging and oxidative stress, cancer, bone diseases, atopic dermatitis, allergies, infections and damage caused by pollutants, mild stress, and depression. Immunomodulation and changes in the intestinal microbiota were the mechanisms most often involved in the observed effects. The results of the studies considered indicated that milk and dairy products are a rich source of beneficial bacteria that should be further exploited to the advantage of human and animal health.

Construction of Probiotic Double-Layered Multinucleated Microcapsules Based on Sulfhydryl-Modified Carboxymethyl Cellulose Sodium for Increased Intestinal Adhesion of Probiotics and Therapy for Intestinal Inflammation Induced by Escherichia coli O157:H7

The decreased number of viable bacteria and the ability of Bifidobacterium to adhere to and colonize the gut in the gastrointestinal environment greatly limit their efficacy. To solve this problem, thiolated carboxymethyl cellulose sodium (CMC) probiotic double-layered multinucleated microcapsules with Bifidobacterium adolescentis FS2-3 in the inner layer and Bacillus subtilis SN15-2 embedded in the outer layers were designed. First, the viable counts and release rates of microcapsules were examined by in vitro simulated digestion assays, and it was found that microcapsules were better protected from gastrointestinal digestion than the controls. Compared with free Bifidobacterium strains, double-layered multinucleated microcapsules have higher viable bacterial survival rates and storage stability. Second, through in vitro rheology, tensile tests, isotherm titration calorimetry, and adhesion tests, it was observed that thiolated CMC could enhance the strong interaction of Bifidobacterium with intestinal mucus and significantly promote the proliferation and growth of probiotics. Finally, double-layered multinucleated microcapsules containing B. adolescentis FS2-3 and B. subtilis SN15-2 modified with sulfhydryl-modified CMC were studied in the intestine. Alleviation of Escherichia coli O157:H7 induced intestinal inflammation. The results showed that microencapsulation could significantly increase the colon content of Bifidobacterium, relieve intestinal inflammation symptoms in mice with bacterial enteritis, and repair the intestinal microbiota disorder caused by inflammation. The probiotic double-layered multinucleated microcapsules prepared in this study can improve the survival rate of probiotics and promote proliferation, adhesion, and colonization of probiotics.

Biological activities and applications of exopolysaccharides produced by lactic acid bacteria: a mini-review

Exopolysaccharides (EPSs) are naturally occurring high-molecular-weight carbohydrates that have been widely studied for their biological activities, including antioxidant, immunomodulatory, anticancer and gut microbiota regulation activities. Polysaccharides are abundant in nature and can be derived from animals, plants, algae, and microorganisms, but among polysaccharides with potential uses, EPSs from microorganisms have the advantages of a short production cycle, high yield, and independence of production from season and climate and thus have broad prospects. While the safety of the producing microorganism can represent a problem in application of microbial EPSs, lactic acid bacteria (LAB) have been used by humans for thousands of years, and they and their products are generally recognized as safe. This makes LAB excellent sources for exopolysaccharides. EPS-producing LAB are readily found in nature. Through screening of strains, optimization of culture conditions, and improvement of the growth medium, the yield of EPSs from LAB can be increased and the scope of application broadened. This review summarizes EPSs from LAB in terms of structure, function and applications, as well as yield optimization, and introduces recent research on the biological activities and practical applications of LAB EPSs, aiming to provide references for researchers in related areas.

A critical review of the recent concept of artificial mechanical uterus design in relation to the maternal microbiome: An Update to past researches

The microbiome in the female reproductive tract plays an essential role in immune modulation and reproductive health. However, various microbes become established during pregnancy, the balance of which plays a crucial role in embryonic development and healthy births. The contribution of disturbances in the microbiome profile to embryo health is poorly understood. A better understanding of the relationship between reproductive outcomes and the vaginal microbiota is needed to optimize the chances of healthy births. In this regards, microbiome dysbiosis refers to conditions in which the pathways of communication and balance within the normal microbiome are imbalanced due to the intrusion of pathogenic microorganisms into the reproductive system. This review summarizes the current state of knowledge on the natural human microbiome, with a focus on the natural uterine microbiome, mother-to-child transmission, dysbiosis, and the pattern of microbial change in pregnancy and parturition, and reviews the effects of artificial uterus probiotics during pregnancy. These effects can be studied in the sterile environment of an artificial uterus, and microbes with potential probiotic activity can be studied as a possible therapeutic approach. The artificial uterus is a technological device or biobag used as an incubator, allowing extracorporeal pregnancy. Establishing beneficial microbial communities within the artificial womb using probiotic species could modulate the immune system of both the fetus and the mother. The artificial womb could be used to select the best strains of probiotic species to fight infection with specific pathogens. Questions about the interactions and stability of the most appropriate probiotics, as well as dosage and duration of treatment, need to be answered before probiotics can be a clinical treatment in human pregnancy.

QseC sensor kinase modulates the human microbiota during enterohemorrhagic Escherichia coli O157:H7 infection in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®)

Enterohemorrhagic Escherichia coli (EHEC) is an important gastrointestinal pathogen known for its ability to cause hemorrhagic colitis and induce hemolytic-uremic syndrome. The inner membrane QseC histidine kinase sensor has shown to be an important regulator of the locus of enterocyte effacement (LEE) island, where important EHEC key virulence genes are located. However, the QseC role during EHEC infection in human microbiota remains unknown. Herein, using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), we investigated whether the QseC sensor has a role in human microbiota modulation by EHEC in a dynamic model. Our data demonstrated that the QseC sensor modulates human microbiota during EHEC infection, and its absence leads to an increase in Lactobacillaceae and Bifidobacterium genus predominance, although non-effect on Bacteroides genus by EHEC strains was observed. In co-culture, the Lactobacillus acidophilus has affected EHEC growth and impaired the EHEC growth under space-niche competition, although no growth difference was observed in the QseC sensor presence. Also, differences in EHEC growth were not detected in competition with Bacteroides thetaiotaomicron and EHEC strains did not affect B. thetaiotaomicron growth either. When investigating the mechanisms behind the SHIME results, we found that hcp-2 expression for the type 6 secretion system, known to be involved in bacterial competition, is under QseC sensor regulation beneath different environmental signals, such as glucose and butyrate. Our findings broaden the knowledge about the QseC sensor in modulating the human microbiota and its importance for EHEC pathogenesis.

Probiotic characterization and comparison of broiler-derived lactobacillus strains based on technique for order preference by similarity to ideal solution analysis

A total of 10 lactobacillus strains were isolated from broiler chickens and their probiotic properties including tolerance to gastrointestinal fluids and heat treatment, antimicrobial activity, adhesion capacity to intestinal cells, surface hydrophobicity, autoaggregation, antioxidative activity, and immunomodulatory effects on chicken macrophages were evaluated. The Limosilactobacillus reuteri (LR) was the most frequently isolated species, followed by Lactobacillus johnsonii (LJ) and Ligilactobacillus salivarius (LS). All isolates showed good resistance to simulated gastrointestinal conditions and antimicrobial activity against 4 indicator strains including Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, and Proteus mirabilis LR 21 exhibited excellent performances on autoaggregation, hydrophobicity and adhesion capacity to Caco-2 intestinal cells. In the meantime, this strain also possessed considerable tolerance to heat treatment, which indicated great potential to be used in the feed industry. However, LJ 20 strain had the highest free radical scavenging activity compared with the other strains. Furthermore, qRT-PCR results revealed that all isolated strains significantly increased the transcriptional levels of proinflammatory genes and tended to induce the M1-type polarization on HD11 macrophages. Particularly, the technique for order preference by similarity to ideal solution (TOPSIS) was adopted in our study to compare and select the most promising probiotic candidate based on in vitro evaluation tests.

Probiotics Interact With Lipids Metabolism and Affect Gut Health

Probiotics have attracted much attention due to their ability to modulate host intestinal microbe, participate in nutrient metabolism or immunomodulatory. Both inflammatory bowel disease (IBD) and bowel cancer are digestive system disease, which have become a global public health problem due to their unclear etiology, difficult to cure, and repeated attacks. Disturbed gut microbiota and abnormal lipid metabolism would increase the risk of intestinal inflammation. However, the link between lipid metabolism, probiotics, and IBD is unclear. In this review, we found that different lipids and their derivatives have different effects on IBD and gut microbes. ω-3 polyunsaturated fatty acids (PUFAs) docosahexaenoic acid, eicosapentaenoic acid, and their derivatives resolvin E1, resolvin D can inhibit oxidative stress and reactive oxygen species activate NFκB and MAPk pathway. While ω-6 PUFAs linoleic acid and arachidonic acid can be derived into leukotrienes and prostaglandins, which will aggravate IBD. Cholesterol can be converted into bile acids to promote lipid absorption and affect microbial survival and colonization. At the same time, it is affected by microbial bile salt hydrolase to regulate blood lipids. Low denstiy lipoprotein (LDL) is easily converted into oxidized LDL, thereby promoting inflammation, while high denstiy lipoprotein (HDL) has the opposite effect. Probiotics compete with intestinal microorganisms for nutrients or ecological sites and thus affect the structure of intestinal microbiota. Moreover, microbial short chain fatty acids, bile salt hydrolase, superoxide dismutase, glutathione, etc. can affect lipid metabolism and IBD. In conclusion, probiotics are directly or indirectly involved in lipids metabolism and their impact on IBD, which provides the possibility to explore the role of probiotics in improving gut health.

Structural insight into protein-protein interactions between intestinal microbiome and host

Protein-protein interactions between the microbiome and host organism play an important role in shaping host health. These host-modulating proteins have therapeutic potential in treating microbiome-linked disorders such as inflammatory bowel disease and obesity. Structural analysis of interacting proteins provides highly mechanistic insight into the domains driving these interactions and the resulting influence on host cell processes. Here, we briefly review recent publication of microbiome protein structures involved in host binding interactions, the effects of these interactions on host physiology, and the need for further study to increase the ability to detect proteins with therapeutic potential.

Effect of D-Ala-Ended Peptidoglycan Precursors on the Immune Regulation of Lactobacillus plantarum Strains

The resistance of Lactobacillus plantarum to vancomycin depends on its peptidoglycan composition. Vancomycin has poor binding affinity with peptidoglycan precursors ending in D-alanyl-D-lactate (D-Ala-D-Lac) but binds strongly to peptidoglycan precursors ending in D-alanyl-D-alanine (D-Ala-D-Ala), resulting in resistance and sensitivity, respectively. The ligase Ddl, which generates D-Ala-D-Lac or D-Ala-D-Ala incorporated into the peptidoglycan precursor chain, is responsible for this specificity. To study the effect of peptidoglycan precursors on immunity, we constructed several strains of L. plantarum expressing the ddl gene of Lactococcus lactis to change their peptidoglycan precursors. The change in the termini of the peptidoglycan precursors was determined by the sensitivity of the strains to vancomycin. The overexpression of ddl increased the susceptibility of the strains to vancomycin. We further explored the regulation of the macrophage inflammatory response pathway by the wild-type and constructed strains, and found that these strains induced the MyD88-dependent TRAF6/MAPK pathway, and the increase in D-Ala L. plantarum peptidoglycan precursors increased the secretion of the inflammatory factors IL-6, IL-1β and TNF-α. These results indicate that D-Ala-ended peptidoglycan precursors play a central role in the variable immunomodulatory ability of L. plantarum.

Lactiplantibacillus plantarum 1201 Inhibits Intestinal Infection of Salmonella enterica subsp. enterica Serovar Typhimurium Strain ATCC 13311 in Mice with High-Fat Diet

Salmonella Typhimurium is widely distributed in food. It can colonise the gastrointestinal tract after ingestion, causing lamina propria edema, inflammatory cell infiltration, and mucosal epithelial decomposition. A high-fat diet (HFD) can induce an inflammatory response, but whether HFD can increase the infection level of S. Typhimurium is unknown. We established a model of Salmonella enterica subsp. enterica serovar Typhimurium strain ATCC 13311 ATCC 13311 infection in healthy adult mice with a maintenance diet (MD) or HFD to explore the effect of Lactiplantibacillus plantarum 1201 intervention on S. Typhimurium ATCC 13311 colonization and its protective effects on mice. HFD exacerbated the infection of S. Typhimurium ATCC 13311, while the intervention of L. plantarum 1201 effectively mitigated this process. L. plantarum 1201 can reduce the colonies of S. ATCC 13311 in the intestines and tissues; and reduce intestinal inflammation by down-regulating the level of TLR4/NF-κB pathway related proteins in serum and the expression of related inflammatory factors in the colon and jejunum. Since L. plantarum 1201 can inhibit the colonization of S. Typhimurium ATCC 13311 and relieve inflammation in HFD, current research may support the use of L. plantarum 1201 to prevent S. Typhimurium infection.

The Probiotic Properties of Lactic Acid Bacteria and Their Applications in Animal Husbandry

The intestinal tract of animals is a complex ecosystem in which nutrients, microbiota and host cells interact extensively. Probiotics can be considered as part of the natural microbiota of the gut and are involved in improving homeostasis. Lactic acid bacteria (LAB) is a general term for a class of non-spore forming, gram-positive bacteria whose main product of fermented sugar is lactic acid. LAB are considered to be a type of probiotic due to their health-promoting effects on the host, and are very effective in the treatment of human and animal diseases. LAB have been widely used as a class of microbial agents in the field of livestock and poultry breeding. They are also considered to be the best substitutes for antibiotics to improve animal health. Here, we review the biological functions, probiotic characteristics and applications of LAB in livestock and poultry breeding. This review is designed to provide a theoretical base for the in-depth exploration and promotion of LAB use in animal diets.

Pediococcus pentosaceus IM96 Exerts Protective Effects against Enterohemorrhagic Escherichia coli O157:H7 Infection In Vivo

Enterohemorrhagic Escherichia coli (EHEC) is a notorious and prevalent foodborne pathogen which can cause serious intestinal diseases. The antagonistic activity of probiotics against EHEC is promising, but most of the studies concerning this subject have been carried out in vitro. Specifically, the interaction between Pediococcus pentosaceus and EHEC O157:H7 in vivo has not been reported yet. In this study, we investigated the protective effect of P. pentosaceus IM96 on EHEC O157:H7-infected female mice in vivo. The results demonstrated that P. pentosaceus IM96 reduced the level of pro-inflammatory factors and increased the level of anti-inflammatory factors of EHEC O157:H7-infected mice. Furthermore, P. pentosaceus IM96 alleviated intestinal mucosal damage and increased the level of MUC-2, tight junction (TJ) proteins, and short chain fatty acids (SCFAs). The intestinal microbial community structure and the diversity and richness of the microbiota were also changed by P. pentosaceus IM96 treatment. In summary, P. pentosaceus IM96 exerted protective effects against EHEC O157:H7 via alleviating intestinal inflammation, strengthening the intestinal barrier function, and regulating intestinal microbiota, suggesting that P. pentosaceus IM96 might serve as a potential microbial agent to prevent and treat intestinal diseases caused by EHEC O157:H7 infection in the future.

Lactobacillus fermentum ZS40 Ameliorates Inflammation in Mice With Ulcerative Colitis Induced by Dextran Sulfate Sodium

Ulcerative colitis is an inflammatory disease of the intestine caused by many reasons, and it may even develop into colon cancer. Probiotics are normal bacteria that exist in the human body and have been proven to regulate the balance of intestinal flora and alleviate inflammation. The current study aimed to study the effect of Lactobacillus fermentum ZS40 (ZS40) on dextran sulfate sodium (DSS)-induced ulcerative colitis mice. The length and weight of the colon were measured, and the histopathological morphological changes of colon tissue were observed to evaluate the effects of ZS40 on colitis. Biochemical kits, ELISA kits, real-time quantitative PCR (RT-qPCR), and western blot were also used to detect the effects of ZS40 on serum and colon tissue related oxidative indicators and pro-inflammatory and anti-inflammatory cytokines. We found that ZS40 could reduce colonic inflammatory cell infiltration and goblet cell necrosis, increase total superoxide dismutase and catalase in mouse serum, and reduce myeloperoxidase and malondialdehyde levels. ZS40 could down-regulate the level of proinflammatory cytokines and up-regulate the level of anti-inflammatory cytokines. More importantly, ZS40 down-regulated the relative expression of nuclear factor-κB p65 (NF-κBp65), IL-6, and TNF-α mRNA and protein, up-regulated the relative expression of inhibitor kapa B alpha (IκB-α). By regulating the NF-κB and MAPK pathways to down-regulated the relative expression of p38 and JNK1/2 mRNA and p38, p-p38, JNK1/2, and p-JNK1/2 proteins. Our study suggested that ZS40 may serve as a potential therapeutical strategy for ulcerative colitis.

Unraveling enterohemorrhagic Escherichia coli infection: the promising role of dietary compounds and probiotics in bacterial elimination and host innate immunity boosting

The innate immune system has developed sophisticated strategies to defense against infections. Host cells utilize the recognition machineries such as toll-like receptors and nucleotide binding and oligomerization domain-like receptors to identify the pathogens and alert immune system. However, some pathogens have developed tactics to evade host defenses, including manipulation of host inflammatory response, interference with cell death pathway, and highjack of phagocytosis signaling for a better survival and colonization in host. Enterohemorrhagic Escherichia coli (EHEC) is a notorious foodborne pathogen that causes severe tissue damages and gastrointestinal diseases, which has been reported to disturb host immune responses. Diverse bioactive compounds such as flavonoids, phenolic acids, alkaloids, saccharides, and terpenoids derived from food varieties and probiotics have been discovered and investigated for their capability of combating bacterial infections. Some of them serve as novel antimicrobial agents and act as immune boosters that harness host immune system. In this review, we will discuss how EHEC, specifically E. coli O157:H7, hijacks the host immune system and interferes with host signaling pathway; and highlight the promising role of food-derived bioactive compounds and probiotics in harnessing host innate immunity and eliminating E. coli O157:H7 infection with multiple strategies.

L. johnsonii, L. plantarum, and L. rhamnosus alleviated Enterohaemorrhagic Escherichia coli-induced diarrhoea in mice by regulating gut microbiota

Enterohaemorrhagic Escherichia coli (EHEC) is a prominent foodborne pathogen that causes infectious intestinal diarrhoea. Lactobacillus is a recognized probiotic that inhibits intestinal pathogens and maintains the balance of the intestinal flora. The purpose of this study was to investigate the regulatory effects of three Lactobacillus strains, L. johnsonii, L. plantarum, and L. rhamnosus, on the intestinal flora of EHEC-infected mice. The initial weight and diarrhoea index of the mice were recorded. After 21 days, the faeces of the mice were subjected to 16S rDNA high-throughput sequencing. The diarrhoea index of mice treated with Lactobacillus improved, their body weight continued to rise, and their liver index gradually decreased. The α diversity analysis showed that the intestinal flora diversity and abundance were lower in mice infected with EHEC than in healthy mice. L. plantarum, L. johnsonii, and L. rhamnosus significantly improved the diversity of the flora species. In terms of flora composition, the three main phyla present were Bacteroidetes, Firmicutes, and Proteobacteria. The abundance of these three phyla was reduced to 93.81% after infection and restored to over 96.30% after treatment. At the genus level, Lactobacillus reduced the abundance of Bacteroides, Helicobacter pylori, and Shigella, while increasing the abundance of butyric acid-producing bacteria and Lactobacillus. Finally, a heat map and non-metric multidimensional scaling analysis showed that the intestinal flora structures in the L. johnsonii, L. plantarum, and L. rhamnosus treatment groups were closest to those of healthy mice. In conclusion, L. johnsonii, L. plantarum, and L. rhamnosus regulated and improved the structure of intestinal flora and relieved diarrhoea caused by EHEC infection.

Bacillus amyloliquefaciens TL Downregulates the Ileal Expression of Genes Involved in Immune Responses in Broiler Chickens to Improve Growth Performance

Bacillus amyloliquefaciens TL promotes broiler chicken performance by improving nutrient absorption and utilization and reducing intestinal inflammation. In this study, RNA-sequencing (RNA-seq)-based transcriptomes of ileal tissues collected from probiotic-fed and control broiler chickens were analyzed to elucidate the effects of the probiotic B. amyloliquefaciens TL, as a feed additive, on the gut immune function. In total, 475 genes were significantly differentially expressed between the ileum of probiotic-fed and control birds. The expression of genes encoding pyruvate kinase, prothymosin-α, and heat stress proteins was high in the ileum of probiotic-fed birds (FPKM > 500), but not in the control group. The gene ontology functional enrichment and pathway enrichment analyses revealed that the uniquely expressed genes in the control group were mostly involved in immune responses, whereas those in the probiotic group were involved in fibroblast growth factor receptor signaling pathways and positive regulation of cell proliferation. Bacillus amyloliquefaciens TL downregulated the expression of certain proinflammatory factors and affected the cytokine–cytokine receptor interaction pathway. Furthermore, B. amyloliquefaciens TL in broiler diets altered the expression of genes involved in immune functions in the ileum. Thus, it might contribute to improved broiler growth by regulating the immune system and reducing intestinal damage in broilers.

Bile salt hydrolase-overexpressing Lactobacillus strains can improve hepatic lipid accumulation in vitro in an NAFLD cell model

Background

Non-alcoholic fatty liver disease (NAFLD) includes a range of liver diseases that occur in the absence of significant alcohol consumption. The probiotic bacterial strains Lactobacillus casei LC2W, which overexpresses the bile salt hydrolase (BSH) gene (referred to as pWQH01), and Lactobacillus plantarum AR113, which exhibits high BSH activity, have been shown to improve hepatic lipid accumulation and may lower cholesterol levels in vivo. These effects may be BSH-dependent, as L. casei LC2W without BSH activity did not exert these beneficial effects.

Objective

This study aimed to investigate the effects of Lactobacillus with high BSH activity on cholesterol accumulation and lipid metabolism abnormalities in oleic acid (OA)- and cholesterol-induced HepG2 cell models, and to determine the mechanism underlying the effects.

Design

A HepG2 cell model of OA-induced steatosis and cholesterol-induced cholesterol accumulation was developed. OA- and cholesterol-treated HepG2 cells were incubated with L. plantarum AR113, L. casei LC2W or L. casei pWQH01 for 6 h at 37°C with 5% CO₂. Subsequently, a series of indicators and gene expressions were analysed.

Results

Both L. plantarum AR113 and L. casei pWQH01 significantly reduced lipid accumulation, total cholesterol (TC) levels and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) mRNA expression relative to the control group, whereas L. casei LC2W had no similar effect. Additionally, exposure to L. plantarum AR113 or L. casei pWQH01 significantly reduced the expression of sterol regulatory element-binding protein 1c (SREBP-1c), Acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS) and tumour necrosis factor-α (TNF-α) andsignificantly increased the expression of 5' adenosine monophosphate-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor alpha (PPARα).

Conclusion

Both L. plantarum AR113 and L. casei pWQH01 appear to improve steatosis in vitro in a BSH-dependent manner.