Anti-inflammatory Effect of Probiotic Limosilactobacillus reuteri KUB-AC5 Against Salmonella Infection in a Mouse Colitis Model

Microbial Contamination of Food: Probiotics and Postbiotics as Potential Biopreservatives

Microbial contamination of food and alimentary toxoinfection/intoxication in humans are commonly caused by bacteria such as Salmonella spp., Escherichia coli, Yersinia spp., Campylobacter spp., Listeria monocytogenes, and fungi (Aspergillus, Fusarium). The addition of probiotic cultures (bacterial strains Lactobacillus and Bifidobacterium and the yeast Saccharomyces cerevisiae var. boulardii) to food contributes primarily to food enrichment and obtaining a functional product, but also to food preservation. Reducing the number of viable pathogenic microorganisms and eliminating or neutralizing their toxins in food is achieved by probiotic-produced antimicrobial substances such as organic acids (lactic acid, acetic acid, propionic acid, phenylacetic acid, and phenyllactic acid), fatty acids (linoleic acid, butyric acid, caproic acid, and caprylic acid), aromatic compounds (diacetyl, acetaldehyde, reuterin), hydrogen peroxide, cyclic dipeptides, bacteriocins, and salivabactin. This review summarizes the basic facts on microbial contamination and preservation of food and the potential of different probiotic strains and their metabolites (postbiotics), including the mechanisms of their antimicrobial action against various foodborne pathogens. Literature data on this topic over the last three decades was searched in the PubMed, Scopus, and Google Scholar databases, systematically presented, and critically discussed, with particular attention to the advantages and disadvantages of using probiotics and postbiotics as food biopreservatives.

Probiotic Limosilactobacillus reuteri KUB-AC5 decreases urothelial cell invasion and enhances macrophage killing of uropathogenic Escherichia coli in vitro study

Introduction

Bacterial urinary tract infections (UTI) are among the most common infectious diseases worldwide. The rise of multidrug-resistant (MDR) uropathogenic Escherichia coli (UPEC) UTI cases is a significant threat to healthcare systems. Several probiotic bacteria have been proposed as an alternative to combat MDR UTI. Lactic acid bacteria in the genus Limosilactobacillus are some of the most studied and used probiotics. However, strain-specific effects play a critical role in probiotic properties. L. reuteri KUB-AC5 (AC5), isolated from the chicken gut, confers antimicrobial and immunobiotic effects against some human pathogens. However, the antibacterial and immune modulatory effects of AC5 on UPEC have never been explored.

Methods

Here, we investigated both the direct and indirect effects of AC5 against UPEC isolates (UTI89, CFT073, and clinical MDR UPEC AT31) in vitro. Using a spot-on lawn, agar-well diffusion, and competitive growth assays, we found that viable AC5 cells and cell-free components of this probiotic significantly reduced the UPEC growth of all strains tested. The human bladder epithelial cell line UM-UC-3 was used to assess the adhesion and pathogen-attachment inhibition properties of AC5 on UPEC.

Results and discussion

Our data showed that AC5 can attach to UM-UC-3 and decrease UPEC attachment in a dose-dependent manner. Pretreatment of UPEC-infected murine macrophage RAW264.7 cells with viable AC5 (multiplicity of infection, MOI = 1) for 24 hours enhanced macrophage-killing activity and increased proinflammatory (Nos2, Il6, and Tnfa) and anti-inflammatory (Il10) gene expression. These findings indicate the gut-derived AC5 probiotic could be a potential urogenital probiotic against MDR UTI.

Current research progress, opportunities, and challenges of Limosillactobacillus reuteri-based probiotic dietary strategies

Limosillactobacillus reuteri (L. reuteri), a type of Lactobacillus spp., stands out as the most extensively researched probiotic. Its remarkable intestinal adhesion has led to widespread applications in both the food and medical sectors. Notably, recent research highlights the probiotic efficacy of L. reuteri sourced from breast milk, particularly in influencing social behavior and mitigating atopic dermatitis. In this review, our emphasis is on surveying recent literature regarding the promotion of host's health by L. reuteri. We aim to provide a concise summary of the latest regulatory effects and potential mechanisms attributed to L. reuteri in the realms of metabolism, brain- and immune-related functions. The mechanism through which L. reuteri promotes host health by modulating the intestinal microenvironment primarily involves promoting intestinal epithelial renewal, bolstering intestinal barrier function, regulating gut microbiota and its metabolites, and suppressing inflammation and immune responses. Additionally, this review delves into new technologies, identifies shortcomings, and addresses challenges in current L. reuteri research. Finally, the application prospects of L. reuteri are provided. Therefore, a better understanding of the role and mechanisms of L. reuteri will contribute significantly to the development of new probiotic functional foods and enable precise, targeted interventions for various diseases.

Defined Pig Microbiota Mixture as Promising Strategy against Salmonellosis in Gnotobiotic Piglets

Probiotics are a potential strategy for salmonellosis control. A defined pig microbiota (DPM) mixture of nine bacterial strains previously exhibited probiotic and anti-Salmonella properties in vitro. Therefore, we evaluated its gut colonization ability and protection effect against S. typhimurium LT2-induced infection in the gnotobiotic piglet model. The DPM mixture successfully colonized the piglet gut and was stable and safe until the end of the experiment. The colon was inhabited by about 9 log CFU g-1 with a significant representation of bifidobacteria and lactobacilli compared to ileal levels around 7-8 log CFU g-1. Spore-forming clostridia and bacilli seemed to inhabit the environment only temporarily. The bacterial consortium contributed to the colonization of the gut at an entire length. The amplicon profile analysis supported the cultivation trend with a considerable representation of lactobacilli with bacilli in the ileum and bifidobacteria with clostridia in the colon. Although there was no significant Salmonella-positive elimination, it seems that the administered bacteria conferred the protection of infected piglets because of the slowed delayed infection manifestation without translocations of Salmonella cells to the blood circulation. Due to its colonization stability and potential protective anti-Salmonella traits, the DPM mixture has promising potential in pig production applications. However, advanced immunological tests are needed.

An Isofibrous Diet with Fiber Konjac Glucomannan Ameliorates Salmonella typhimurium-Induced Colonic Injury by Regulating TLR2-NF-κB Signaling and Intestinal Microbiota in Mice

This study aimed to investigate the hypothesis that dietary konjac glucomannan (KGM) could alleviate Salmonella typhimurium-induced colitis by modulating intestinal microbiota. Mice were fed an isocaloric and isofibrous diet supplemented with either 7% KGM or cellulose and were treated with 5 × 108 CFU of S. typhimurium. The results showed that KGM had an average molecular weight of 936 kDa and predominantly consisted of mannose and glucose at a molar ratio of 1:1.22. In vivo studies demonstrated that dietary KGM effectively mitigated colonic lesions, oxidative stress, disruption of tight junction protein 2 and occludin, and the inflammatory response induced by S. typhimurium. Moreover, KGM administration alleviated the dramatic upregulation of toll-like receptor 2 (TLR2) and phosphonuclear factor κB (NF-κB) protein abundance, induced by Salmonella treatment. Notably, dietary KGM restored the reduced Muribaculaceae and Lactobacillus abundance and increased the abundance of Blautia and Salmonella in S. typhimurium-infected mice. Spearman correlation analysis revealed that the gut microbiota improved by KGM contribute to inhibit inflammation and oxidative stress. These results demonstrated the protective effects of dietary KGM against colitis by modulating the gut microbiota and the TLR2-NF-κB signaling pathway in response to Salmonella infection.

Preliminary characterization of gut mycobiome enterotypes reveals the correlation trends between host metabolic parameter and diet: a case study in the Thai Cohort

The association between the gut mycobiome and its potential influence on host metabolism in the Thai Cohort was assessed. Two distinct predominant enterotypes, Saccharomyces (Sa) and Aspergillus/Penicillium (Ap/Pe) showed differences in gut mycobiota diversity and composition. Notably, the Sa enterotype exhibited lower evenness and richness, likely due to the prevalence of Saccharomyces, while both enterotypes displayed unique metabolic behaviors related to nutrient metabolism and body composition. Fiber consumption was positively correlated with adverse body composition and fasting glucose levels in individuals with the Sa enterotype, whereas in the Ap/Pe enterotype it was positively correlated with fat and protein intake. The metabolic functional analysis revealed the Sa enterotype associated with carbohydrate metabolism, while the Ap/Pe enterotype involved in lipid metabolism. Very interestingly, the genes involved in the pentose and glucuronate interconversion pathway, such as polygalacturonase and L-arabinose-isomerase, were enriched in the Sa enterotype signifying a metabolic capacity for complex carbohydrate degradation and utilization of less common sugars as energy sources. These findings highlight the interplay between gut mycobiome composition, dietary habits, and metabolic outcomes within the Thai cohort studies.

Synergistic activity of Limosilactobacillus reuteri KUB-AC5 and water-based plants against Salmonella challenge in a human in vitro gut model

A synbiotic is a combination of live microorganisms and specific substrates that are selectively utilized by host microorganisms, resulting in health benefits for the host. Previous studies have demonstrated the protective effects of L. reuteri KUB-AC5 against Salmonella infection in chicken and mouse models. The probiotic activity of L. reuteri KUB-AC5 in these hosts was influenced by nutritional supplements. Water-based plants contain significant amounts of carbohydrates, particularly dietary fiber and proteins, making them potential prebiotic substrates. In this study, four water-based plants (Ulva rigida, Caulerpa lentillifera, Wolffia globosa, and Gracillaria fisheri) were screened for their ability to support the growth of L. reuteri KUB-AC5. Under monoculture testing, U. rigida exhibited the highest capacity to support the growth of L. reuteri KUB-AC5 and the production of organic acids, including acetic acid, lactic acid, and propionic acid (p ≤ 0.05). In co-culture experiments, the synbiotic combination of U. rigida and L. reuteri KUB-AC5 demonstrated the potential to eliminate Salmonella Typhimurium DMST 48437 when inoculated at 104 CFU/mL within 9 h. The synbiotic activities of U. rigida and L. reuteri KUB-AC5 were further investigated using an in vitro human gut model. Compared to the probiotic treatment, the synbiotic combination of L. reuteri KUB-AC5 and U. rigida showed significantly higher levels of L. reuteri KUB-AC5 (5.1 log copies/mL) and a reduction of S. Typhimurium by 0.8 log (CFU/ml) after 24 h (p ≤ 0.05). Synbiotic treatment also significantly promoted the production of short-chain fatty acids (SCFAs), including butyric acid, propionic acid, and acetic acid, compared to prebiotic and probiotic treatments alone (p ≤ 0.05). Furthermore, the synbiotic formulation modulated the in vitro simulated gut microbiome, enhancing putatively beneficial gut microbes, including lactobacilli, Faecalibacterium, and Blautia. Our findings demonstrated that L. reuteri KUB-AC5, in combination with U. rigida, exhibited synergistic activity, as indicated by increased viability, higher anti-pathogenicity toward Salmonella, and the ability to modulate the gut microbiome.

Identification and characterization of potential probiotic lactic acid bacteria isolated from pig feces at various production stages

Lactic acid bacteria (LAB) were isolated, identified, and characterized from pig feces at various growth stages and feed rations in order to be used as probiotic feed additives. Lactic acid bacteria numbers ranged from 7.10 ± 1.50 to 9.40 log CFUs/g for growing and lactating pigs, respectively. Isolates (n = 230) were identified by (GTG)5-polymerase chain reaction and partial sequence analysis of 16S rRNA. Major LAB populations were Limosilactobacillus reuteri (49.2%), Pediococcus pentosaceus (20%), Lactobacillus amylovorus (11.4%), and L. johnsonii (8.7%). In-vitro assays were performed, including surface characterization and tolerance to acid and bile salts. Several lactobacilli exhibited hydrophobic and aggregative characteristics and were able to withstand gastrointestinal tract conditions. In addition, lactobacilli showed starch- and phytate-degrading ability, as well as antagonistic activity against Gram-negative pathogens and the production of bacteriocin-like inhibitory substances. When resistance or susceptibility to antibiotics was evaluated, high phenotypic resistance to ampicillin, gentamicin, kanamycin, streptomycin, and tetracycline and susceptibility towards clindamycin and chloramphenicol was observed in the assayed LAB. Genotypic characterization showed that 5 out of 15 resistance genes were identified in lactobacilli; their presence did not correlate with phenotypic traits. Genes erm(B), strA, strB, and aadE conferring resistance to erythromycin and streptomycin were reported among all lactobacilli, whereas tet(M) gene was harbored by L. reuteri and L. amylovorus strains. Based on these results, 6 probiotic LAB strains (L. reuteri F207R/G9R/B66R, L. amylovorus G636T/S244T, and L. johnsonii S92R) can be selected to explore their potential as direct feed additives to promote swine health and replace antibiotics.

Chromatin Accessibility and Transcriptional Landscape during Inhibition of Salmonella enterica by Lactobacillus reuteri in IPEC-J2 Cells

Lactobacillus reuteri is a probiotic with bacteriostatic effects, which can effectively inhibit the activity of pathogens. However, the molecular mechanism underlying the inhibition of pathogens by L. reuteri in intestinal cells remains unclear. Using the porcine intestinal cell line IPEC-J2 as a model, we combined RNA-seq and ATAC-seq methods to delineate the porcine genome-wide changes in biological processes and chromatin accessibility in IPEC-J2 cells stimulated by Salmonella enterica BNCC186354, as well as L. reuteri ATCC 53608. Overall, we found that many porcine transcripts were altered after S. enterica BNCC186354 treatment, while L. reuteri ATCC 53608 treatment partially restored this alteration, such as salmonella infection and PI3K/AKT and MAPK pathways. Combined analysis of these two datasets revealed that 26 genes with similar trends overlapped between gene expression and chromatin accessibility. In addition, we identified potential host functional transcription factors (TFs), such as GATA1, TAL1, TBP, RUNX1, Gmeb1, Gfi1b, RARA, and RXRG, in IPEC-J2 cells that might play a critical role and are targeted by L. reuteri ATCC 53608. Moreover, we verified that PI3K/AKT, MAPK, and apoptosis pathways are potentially regulated by S. enterica BNCC186354 but restored by L. reuteri ATCC 53608. The PI3K/AKT pathway was activated by L. reuteri ATCC 53608, thereby potentially inhibiting S. enterica BNCC186354 infection. In conclusion, our data provide new insights into the expression pattern of functional genes and the epigenetic alterations in IPEC-J2 cells underlying the bacteriostatic action of L. reuteri ATCC 53608.

Dietary shredded steam-exploded pine particle supplementation as a strategy to mitigate chronic cyclic heat stress by modulating gut microbiota in broilers

Improving the availability of underutilized waste for the economic use of livestock feed can be important in countries where feed grain production is scarce. Modulating the gut microbiota through the fibrous content present in these wastes may help mitigate the adverse effects of heat stress (HS). Here, we investigated the effects of dietary steam-exploded pine particle (SPP), a value-added waste product, on the performance, gut health, and cecum microbiota in heat-stressed broilers. Ross 308 broilers (n = 180) at 29 days of age were distributed into three dietary treatment groups (0%, 1%, and 2% SPP) and two temperature conditions (NT: 21 °C; CHS: 31 °C) and grown for seven days. CHS, but not SPP, adversely affected performance parameters, but SPP did not interactively modulate these results. On the contrary, both differently affected other parameters. CHS resulted in increased rectal temperature, total protein in serum, and Nox4 gene expression, whereas 2% SPP increased GLP-2 and the Nox4 gene expression in the duodenum in comparison to 0% and 1% SPP. CHS significantly modified the beta-diversity of cecal microbiota while 1% SPP supplementation in diets increased the abundance of the favorable bacterial genera in chicken. Concludingly, CHS adversely affects growth performances, gut health, stress-related genes, and cecal microbiota while dietary 1% SPP may facilitate the proliferation of beneficial microorganisms in the cecum of broilers.

Immunostimulatory Activity of Lactic Acid Bacteria Cell-Free Supernatants through the Activation of NF-κB and MAPK Signaling Pathways in RAW 264.7 Cells

Lactic acid bacteria (LAB) can improve host health and has strong potential for use as a health functional food. Specific strains of LAB have been reported to exert immunostimulatory effects. The primary goal of this study was to evaluate the immunostimulatory activities of novel LAB strains isolated from humans and foods and to investigate the probiotic properties of these strains. Cell-free supernatants (CFS) obtained from selected LAB strains significantly increased phagocytosis and level of nitric oxide (NO) and pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 in RAW264.7 macrophage cells. The protein expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2, which are immunomodulators, was also upregulated by CFS treatment. CFS markedly induced the phosphorylation of nuclear factor-κB (NF-κB) and MAPKs (ERK, JNK, and p38). In addition, the safety of the LAB strains used in this study was demonstrated by hemolysis and antibiotic resistance tests. Their stability was confirmed under simulated gastrointestinal conditions. Taken together, these results indicate that the LAB strains selected in this study could be useful as probiotic candidates with immune-stimulating activity.

Therapeutic effects of oral administration of lytic Salmonella phages in a mouse model of non-typhoidal salmonellosis

Acute non-typhoidal salmonellosis (NTS) caused by a Gram-negative bacterium Salmonella enterica serovar Typhimurium (S. Tm) is one of the most common bacterial foodborne diseases worldwide. Bacteriophages (phages) can specifically target and lyse their host bacteria, including the multidrug-resistant strains, without collateral damage to other bacteria in the community. However, the therapeutic use of Salmonella phages in vivo is still poorly investigated. Salmonella phages ST-W77 and SE-W109 have previously been shown by our group to be useful for biocontrol properties. Here, we tested whether phages ST-W77 and SE-W109 can reduce Salmonella invasion into cultured human cells and confer a therapeutic benefit for acute NTS in a mammalian host. Human colonocytes, T84 cells, were treated with phages ST-W77, SE-W109, and its combination for 5 min before S. Tm infection. Gentamicin protection assays demonstrated that ST-W77 and SE-W109 significantly reduced S. Tm invasion and inflammatory response in human colonocytes. Next, streptomycin-pretreated mice were orally infected with S. Tm (108 CFU/mouse) and treated with a single or a combination of ST-W77 and SE-W109 (1010 PFU/mouse for 4 days) by oral feeding. Our data showed that phage-treated mice had lower S. Tm numbers and tissue inflammation compared to the untreated mice. Our study also revealed that ST-W77 and SE-W109 persist in the mouse gut lumen, but not in systemic sites. Together, these data suggested that Salmonella phages ST-W77 and SE-W109 could be further developed as an alternative approach for treating an acute NTS in mammalian hosts.

Evolving Experimental Platforms to Evaluate Ulcerative Colitis

Ulcerative colitis (UC) is a multifactorial disease defined by chronic intestinal inflammation with idiopathic origins. It has a predilection to affect the mucosal lining of the large intestines and rectum. Management of UC depends upon numerous factors that include disease pathogenesis and severity that are maintained via medical or surgical means. Chronic inflammation that is left untreated or managed poorly from a clinical stance can result in intestinal ulceration accompanied by resulting physiological dysfunction. End-stage UC is mediated by surgical intervention with the resection of diseased tissue. This can lead to numerous health-related quality of life issues but is considered a curative approach. Regimens to treat UC are ever evolving and find their basis within various platforms to evaluate and treat UC. Numerous modeling systems have been examined to delineate potential mechanisms of action. However, UC is a heterogenous disease spanning unknown genetic origins coupled with environmental factors that can influence disease outcomes and related treatment procedures. Unfortunately, there is no one-size-fits-all model to fully assess all facets of UC. Within the context of this review article, the utility of various approaches that have been employed to gain insight into different aspects of UC will be investigated.

Study on the antagonistic effects of koumiss on Toxoplasma gondii infection in mice

Toxoplasma gondii is an important food-borne zoonotic parasite, and approximately one-third of people worldwide are positive for T. gondii antibodies. To date, there are no specific drugs or vaccines against T. gondii. Therefore, developing a new safe and effective method has become a new trend in treating toxoplasmosis. Koumiss is rich in probiotics and many components that can alleviate the clinical symptoms of many diseases via the functional characteristics of koumiss and its regulation of intestinal flora. To investigate the antagonistic effect of koumiss on T. gondii infection, the model of acute and chronic T. gondii infection was established in this study. The survival rate, SHIRPA score, serum cytokine levels, brain cyst counts, β-amyloid deposition and intestinal flora changes were measured after koumiss feeding. The results showed that the clinical symptoms of mice were improved at 6 dpi and that the SHIRPA score decreased after koumiss feeding (P < 0.05). At the same time, the levels of IL-4, IFN-γ and TNF-α decreased (P < 0.001, P < 0.001, P < 0.01). There was no significant difference of survival rate between koumiss treatment and the other groups. Surprisingly, the results of chronic infection models showed that koumiss could significantly reduce the number of brain cysts in mice (P < 0.05), improve β-amyloid deposition in the hippocampus (P < 0.01) and decrease the levels of IFN-γ and TNF-α (P < 0.01, P < 0.05). Moreover, koumiss could influence the gut microbiota function in resisting T. gondii infection. In conclusion, koumiss had a significant effect on chronic T. gondii infection in mice and could improve the relevant indicators of acute T. gondii infection in mice. The research provides new evidence for the development of safe and effective anti-T. gondii methods, as well as a theoretical basis and data support for the use of probiotics against T. gondii infection and broadened thoughts for the development and utilization of koumiss.

Dietary Supplementation of Limosilactobacillus mucosae LM1 Enhances Immune Functions and Modulates Gut Microbiota Without Affecting the Growth Performance of Growing Pigs

Limosilactobacillus mucosae LM1 (LM1) is previously isolated from the intestine of piglets, but its potential as a probiotic supplement has not yet been assessed in growing pigs. In this study, we analyzed the probiotic effect of LM1 on the growth performance, apparent total tract digestibility (ATTD) of nutrients, immune properties, intestinal morphology, and gut microbiota and their metabolites in growing pigs. The experiment included 145 Duroc × (Landrace × Yorkshire) pigs (average body weight: 21.21 ± 1.14 kg) distributed into five treatment groups. The pigs were fed either a control diet (CON), or the control diet supplemented with incremental doses of LM1, namely low-dose LM1 (LL, 8.3 × 108 CFU/kg), moderate-low dose LM1 (ML, 4.2 × 109 CFU/kg), moderate-high dose LM1 (MH, 8.3 × 109 CFU/kg), and high-dose LM1 (HH, 2.1 × 1010 CFU/kg) for 42 d. On d 42, 12 pigs from each of the CON and MH groups were slaughtered. The results indicated that the ATTD of nitrogen (N, P = 0.038) was improved with MH supplementation. In addition, increasing dose of LM1 improved the immune response in pigs by reducing serum pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-alpha) and increasing anti-inflammatory cytokines (interleukin-10). Pigs fed with MH LM1 also had higher jejunal villus height and ileal villus height: crypt depth ratio, demonstrating improved intestinal morphology. Moreover, moderate-high LM1 supplementation enriched SCFA-producing taxa such as Lactobacillus, Holdemanella, Peptococcus, Bifidobacterium, Eubacterium_hallii_group, and Lachnospiraceae_AC2044_group, which correlated positively with increased fecal levels of butyrate and iso-valerate. These results strongly suggest the probiotic potential of LM1 on growing pigs. Overall, the current study provides insights on the use of L. mucosae LM1 as a novel livestock probiotic to improve pig gut health.

Probing Genome-Scale Model Reveals Metabolic Capability and Essential Nutrients for Growth of Probiotic Limosilactobacillus reuteri KUB-AC5

Limosilactobacillus reuteri KUB-AC5 displays the hallmark features of probiotic properties for food and feed industries. Optimization of cultivation condition for the industrial production is important to reach cell concentration and cost reduction. Considering the strain-specific growth physiology, metabolic capability, and essential nutrients of L. reuteri KUB-AC5, the genome-scale metabolic model (GSMM) of L. reuteri KUB-AC5 was developed. Hereby, the GSMM of iTN656 was successfully constructed which contained 656 genes, 831 metabolites, and 953 metabolic reactions. The iTN656 model could show a metabolic capability under various carbon sources and guide potentially 14 essential single nutrients (e.g., vitamin B complex and amino acids) and 2 essential double nutrients (pairwise glutamine-glutamate and asparagine-aspartate) for L. reuteri KUB-AC5 growth through single and double omission analysis. Promisingly, the iTN656 model was further integrated with transcriptome data suggesting that putative metabolic routes as preferable paths e.g., sucrose uptake, nucleotide biosynthesis, urea cycle, and glutamine transporter for L. reuteri KUB-AC5 growth. The developed GSMM offers a powerful tool for multi-level omics analysis, enabling probiotic strain optimization for biomass overproduction on an industrial scale.