Antagonistic trait of Lactobacillus reuteri S5 against Salmonella enteritidis and assessment of its potential probiotic characteristics

Protective effects of carboxymethyl chitosan-dialdehyde glucan/polydopamine carrier-delivered Bacillus subtilis on the intestinal tract of mice infected with Salmonella

This study investigated the protective effects of carboxymethyl chitosan-dialdehyde glucan/polydopamine carrier-delivered Bacillus subtilis (PBS) on Salmonella-induced intestinal inflammation in mice. The results indicated that PBS significantly lowered the organ index and inflammatory factor levels while increasing the levels of oxidase in mice. Interestingly, after PBS intervention, the mRNA expression levels of mucin, tight junction proteins, immune proteins, and transcription factors that constitute the intestinal barrier in mice exhibited a significant increase compared to those in the model group. The intestinal flora results showed that PBS improved the abundance of Ruminococcus, Bacillus, and Roseburia, simultaneously increasing the content of short-chain fatty acids. Furthermore, the downstream protein expression of pathway genes confirmed that PBS inhibited the inflammatory response by regulating the TLR4-NF-κB-NLRP3 inflammasome signaling pathway. These results indicate that carrier protection for Bacillus subtilis can enhance its relief effect on mice infected with Salmonella.

The Impact of Lactobacillus reuteri on Oral and Systemic Health: A Comprehensive Review of Recent Research

Oral diseases, particularly dental caries and periodontal disease, pose significant global health challenges. The imbalance of the oral microbiota plays a key role in the occurrence of these diseases, prompting researchers to seek new strategies to restore oral ecological balance. Lactobacillus reuteri is a Gram-positive rod-shaped bacterium that exists in various body parts of humans, including the gastrointestinal tract, urinary tract, skin, and so on. This species has a potentially positive impact on oral health and plays an important role in maintaining systemic health. Recent studies have explored the application of Lactobacillus reuteri in the prevention and treatment of oral diseases, and its impact on systemic health has also been preliminarily revealed. The current review summarizes the role of Lactobacillus reuteri in oral health and systemic health and outlines its potential applications in the future. Lactobacillus reuteri has shown promising prospects in treating non-communicable biofilm-dependent oral diseases, but its mechanism of action and efficacy still need further research. In addition, Lactobacillus reuteri has also displayed some potential benefits in promoting overall health. Future research should focus on revealing the specific pathways of action of Lactobacillus reuteri, screening for the most beneficial strains, determining the most effective drug delivery strategies, developing oral and systemic health products based on Lactobacillus reuteri, and ensuring their safety in clinical applications.

The novel probiotic preparation based on Lactobacillus spp. mixture on the intestinal bacterial community structure of Cherry Valley duck

The development and utilization of probiotics have many environmental benefits when they are used to replace antibiotics in animal production. In this study, intestinal lactic acid bacteria were isolated from the intestines of Cherry Valley ducks. Probiotic lactic acid bacterial strains were screened for antibacterial activity and tolerance to produce a Lactobacillus spp. mixture. The effects of the compound on the growth performance and intestinal flora of Cherry Valley ducks were studied. Based on the results of the antibacterial activity and tolerance tests, the highly active strains Lactobacillus casei 1.2435, L. salivarius L621, and L. salivarius L4 from the intestines of Cherry Valley ducks were selected. The optimum ratio of L. casei 1.2435, L. salivarius L621, and L. salivarius L4 was 1:1:2, the amount of inoculum used was 1%, and the fermentation time was 14 h. In vivo experiments showed that compared with the control group, the relative abundances of intestinal Lactobacillus and Blautia were significantly increased in the experimental group fed the lactobacilli compound (P < 0.05); the relative abundances of Parabacteroides, [Ruminococcus]_torques_group, and Enterococcus were significantly reduced (P < 0.05), and the growth and development of the dominant intestinal flora were promoted in the Cherry Valley ducks. This study will provide more opportunities for Cherry Valley ducks to choose microecological agents for green and healthy breeding.

Emerging Approaches for Mitigating Biofilm-Formation-Associated Infections in Farm, Wild, and Companion Animals

The importance of addressing the problem of biofilms in farm, wild, and companion animals lies in their pervasive impact on animal health and welfare. Biofilms, as resilient communities of microorganisms, pose a persistent challenge in causing infections and complicating treatment strategies. Recognizing and understanding the importance of mitigating biofilm formation is critical to ensuring the welfare of animals in a variety of settings, from farms to the wild and companion animals. Effectively addressing this issue not only improves the overall health of individual animals, but also contributes to the broader goals of sustainable agriculture, wildlife conservation, and responsible pet ownership. This review examines the current understanding of biofilm formation in animal diseases and elucidates the complex processes involved. Recognizing the limitations of traditional antibiotic treatments, mechanisms of resistance associated with biofilms are explored. The focus is on alternative therapeutic strategies to control biofilm, with illuminating case studies providing valuable context and practical insights. In conclusion, the review highlights the importance of exploring emerging approaches to mitigate biofilm formation in animals. It consolidates existing knowledge, highlights gaps in understanding, and encourages further research to address this critical facet of animal health. The comprehensive perspective provided by this review serves as a foundation for future investigations and interventions to improve the management of biofilm-associated infections in diverse animal populations.

Lactobacillus plantarum supernatant inhibits growth of Riemerella anatipestifer and mediates intestinal antimicrobial defense in Muscovy ducks

Riemerella anatipestifer (RA) is an important pathogen of waterfowl, with multiple serotypes and a lack of cross-protection between each serotype, which leads to the continued widespread in the world and causing significant economic losses to the duck industry. Thus, prevention and inhibition of RA infection are of great concern. Previous research has established that Lactobacillus plantarum supernatant (LPS) can prevents the pathogenic bacteria infection. However, LPS whether inhibits RA and underlying mechanisms have not yet been clarified. In this study, we investigated the direct and indirect effects of LPS-ZG7 against RA infection in Muscovy ducks. The results demonstrated that LPS-ZG7 prevented RA growth in the presence of pH-neutralized, and the inhibition was relatively stable and unaffected by heat, acid-base and ultraviolet light (UV). Following flow cytometry data found that LPS-ZG7 increased RA membrane permeability and leakage of intracellular molecules. And scanning electron microscopy revealed LPS-ZG7 damaged the RA membrane integrity and leading to RA death. Furthermore, quantitative real time polymerase chain reaction (qPCR) analysis represented that LPS-ZG7 upregulated mucosal tight junction proteins occludin, claudin-1, and Zo-1 in Muscovy ducks, and increasing mucosal transport channels SGLT-1, PepT1, AQP2, AQP3, and AQP10 in duodenum, jejunum, and colon, then decreased the intestinal permeability and intestinal barrier disruption which were caused from RA. From the data, it is apparent that LPS-ZG7 enhanced intestinal mucosal integrity by rising villus height, villus height-to-crypt depth ratio and lower crypt depth. LPS-ZG7 significantly decreased intestinal epithelia cells apoptosis caused by RA invasion, and enhanced intestinal permeability and contribute to barrier dysfunction, ultimately improving intestinal health of host, indirectly leading to reduce diarrhea rate and mortality caused by RA. Overall, this study strengthens the idea that LPS-ZG7 directly inhibited the RA growth by increased RA membrane permeability and damaged the RA membrane integrity, and then indirectly enhanced intestinal mucosal integrity, improved intestinal health of host and mediated intestinal antimicrobial defense.

The protective role of commensal gut microbes and their metabolites against bacterial pathogens

Multidrug-resistant microorganisms have become a major public health concern around the world. The gut microbiome is a gold mine for bioactive compounds that protect the human body from pathogens. We used a multi-omics approach that integrated whole-genome sequencing (WGS) of 74 commensal gut microbiome isolates with metabolome analysis to discover their metabolic interaction with Salmonella and other antibiotic-resistant pathogens. We evaluated differences in the functional potential of these selected isolates based on WGS annotation profiles. Furthermore, the top altered metabolites in co-culture supernatants of selected commensal gut microbiome isolates were identified including a series of dipeptides and examined for their ability to prevent the growth of various antibiotic-resistant bacteria. Our results provide compelling evidence that the gut microbiome produces metabolites, including the compound class of dipeptides that can potentially be applied for anti-infection medication, especially against antibiotic-resistant pathogens. Our established pipeline for the discovery and validation of bioactive metabolites from the gut microbiome as novel candidates for multidrug-resistant infections represents a new avenue for the discovery of antimicrobial lead structures.

Lactiplantibacillus plantarum Postbiotics Suppress Salmonella Infection via Modulating Bacterial Pathogenicity, Autophagy and Inflammasome in Mice

Our study aimed to explore the effects of postbiotics on protecting against Salmonella infection in mice and clarify the underlying mechanisms. Eighty 5-week-old C57BL/6 mice were gavaged daily with Lactiplantibacillus plantarum (LP)-derived postbiotics (heat-killed bacteria, LPBinactive; culture supernatant, LPC) or the active bacteria (LPBactive), and gavaged with Salmonella enterica Typhimurium (ST). The Turbidimetry test and agar diffusion assay indicated that LPC directly inhibited Salmonella growth. Real-time PCR and biofilm inhibition assay showed that LPC had a strong ability in suppressing Salmonella pathogenicity by reducing virulence genes (SopE, SopB, InvA, InvF, SipB, HilA, SipA and SopD2), pili genes (FilF, SefA, LpfA, FimF), flagellum genes (FlhD, FliC, FliD) and biofilm formation. LP postbiotics were more effective than LP on attenuating ST-induced intestinal damage in mice, as indicated by increasing villus/crypt ratio and increasing the expression levels of tight junction proteins (Occludin and Claudin-1). Elisa assay showed that LP postbiotics significantly reduced ST-induced inflammation by regulating the levels of inflammatory cytokines (the increased IL-4 and IL-10 and the decreased TNF-α) in serum and ileum (p < 0.05). Furthermore, LP postbiotics inhibited the activation of NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome by decreasing the protein expression of NLRP3 and Caspase-1, and the gene expression of Caspase-1, IL-1β and IL-18. Meanwhile, both LPC and LPB observably activated autophagy under ST infection, as indicated by the up-regulated expression of LC3 and Beclin1 and the downregulated p62 level (p < 0.05). Finally, we found that LP postbiotics could trigger an AMP-activated protein kinase (AMPK) signaling pathway to induce autophagy. In summary, Lactiplantibacillus plantarum-derived postbiotics alleviated Salmonella infection via modulating bacterial pathogenicity, autophagy and NLRP3 inflammasome in mice. Our results confirmed the effectiveness of postbiotics agents in the control of Salmonella infection.

Probiotic Escherichia coli Nissle 1917 protect chicks from damage caused by Salmonella enterica serovar Enteritidis colonization

As a foodborne pathogen of global importance, Salmonella enterica serovar Enteritidis (S. Enteritidis) is a threat to public health that is mainly spread by poultry products. Intestinal Enterobacteriaceae can inhibit the colonization of S. Enteritidis and are regarded as a potential antibiotic substitute. We investigated, in chicks, the anti-S. Enteritidis effects of Escherichia coli (E. coli) Nissle 1917, the most well-known probiotic member of Enterobacteriaceae. Eighty 1-d-old healthy female AA broilers were randomly divided into 4 groups, with 20 in each group, namely the negative control (group P), the E. coli Nissle 1917-treated group (group N), the S. Enteritidis-infected group (group S) and the E. coli Nissle 1917-treated and S. Enteritidis-infected group (group NS). From d 5 to 7, chicks in groups N and NS were orally gavaged once a day with E. coli Nissle 1917 and in groups P and S were administered the same volume of sterile PBS. At d 8, the chicks in groups S and NS were orally gavaged with S. Enteritidis and in groups P and N were administered the same volume of sterile PBS. Sampling was conducted 24 h after challenge. Results showed that gavage of E. coli Nissle 1917 reduced the spleen index, Salmonella loads, and inflammation (P < 0.05). It improved intestinal morphology and intestinal barrier function (P < 0.05). S. Enteritidis infection significantly reduced mRNA expression of angiotensin-converting enzyme 2 (ACE2) and solute carrier family 6-member 19 (SLC6A19) in the cecum and the content of Gly, Ser, Gln, and Trp in the serum (P < 0.05). Pretreatment with E. coli Nissle 1917 yielded mRNA expression of ACE2 and SLC6A19 in the cecum and levels of Gly, Ser, Gln, and Trp in the serum similar to that of uninfected chicks (P < 0.05). Additionally, E. coli Nissle 1917 altered cecum microbiota composition and enriched the abundance of E. coli, Lactobacillales, and Lachnospiraceae. These findings reveal that the probiotic E. coli Nissle 1917 reduced S. Enteritidis infection and shows enormous potential as an alternative to antibiotics.

Sodium Humate-Derived Gut Microbiota Ameliorates Intestinal Dysfunction Induced by Salmonella Typhimurium in Mice

Salmonella is a foodborne pathogen that is one of the main causes of gastroenteric disease in humans and animals. As a natural organic substance, sodium humate (HNa) possesses antibacterial, antidiarrheal, and anti-inflammatory properties. However, it is unclear whether the HNa and HNa-derived microbiota exert alleviative effects on Salmonella enterica serovar Typhimurium-induced enteritis. We found that treatment with HNa disrupted the cell wall of S. Typhimurium and decreased the virulence gene expression. Next, we explored the effect of HNa presupplementation on S. Typhimurium-induced murine enteritis. The results revealed that HNa ameliorated intestinal pathological damage. In addition, we observed that presupplementation with HNa enhanced intestinal barrier function via modulating gut microbiota, downregulating toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) and NOD-like receptor protein 3 (NLRP3) signaling pathways, regulating intestinal mucosal immunity, and enhancing tight junction protein expression. To further validate the effect of HNa-derived microbiota on S. Typhimurium-induced enteritis, we performed fecal microbiota transplantation and found that HNa-derived microbiota also alleviated S. Typhimurium-induced intestinal damage. It is noteworthy that both HNa and HNa-derived microbiota improved the liver injury caused by S. Typhimurium infection. Collectively, this is the first study to confirm that HNa could alleviate S. Typhimurium-induced enteritis in a gut microbiota-dependent manner. This study provides a new perspective on HNa as a potential drug to prevent and treat salmonellosis. IMPORTANCE Salmonella Typhimurium is an important zoonotic pathogen, widely distributed in nature. S. Typhimurium is one of the leading causes of foodborne illnesses worldwide, and more than 350,000 people died from Salmonella infection each year, which poses a substantial risk to public health and causes a considerable economic loss. Here, we found that the S. Typhimurium infection caused severe intestinal and liver damage. In addition, we first found that sodium humate (HNa) and HNa-derived gut microbiota can alleviate S. Typhimurium infection-induced intestinal damage. These findings extend the knowledge about the public health risk and pathogenic mechanisms of S. Typhimurium.

Defined Pig Microbiota with a Potential Protective Effect against Infection with Salmonella Typhimurium

A balanced microbiota is a main prerequisite for the host's health. The aim of the present work was to develop defined pig microbiota (DPM) with the potential ability to protect piglets against infection with Salmonella Typhimurium, which causes enterocolitis. A total of 284 bacterial strains were isolated from the colon and fecal samples of wild and domestic pigs or piglets using selective and nonselective cultivation media. Isolates belonging to 47 species from 11 different genera were identified by MALDI-TOF mass spectrometry (MALDI-TOF MS). The bacterial strains for the DPM were selected for anti-Salmonella activity, ability to aggregate, adherence to epithelial cells, and to be bile and acid tolerant. The selected combination of 9 strains was identified by sequencing of the 16S rRNA gene as Bacillus sp., Bifidobacterium animalis subsp. lactis, B. porcinum, Clostridium sporogenes, Lactobacillus amylovorus, L. paracasei subsp. tolerans, Limosilactobacillus reuteri subsp. suis, and Limosilactobacillus reuteri (two strains) did not show mutual inhibition, and the mixture was stable under freezing for at least 6 months. Moreover, strains were classified as safe without pathogenic phenotype and resistance to antibiotics. Future experiments with Salmonella-infected piglets are needed to test the protective effect of the developed DPM.

Effect of Limosilactobacillus reuteri ZJF036 on Growth Performance and Gut Microbiota in Juvenile Beagle Dogs

This experiment investigated the effects of Limosilactobacillus reuteri ZJF036 on growth performance, serum biochemical parameters, and gut microbiota in beagle dogs. Sixteen 75 ± 5-day-old healthy male beagles (4.51 ± 1.37 kg) were randomly divided into two groups; the experimental group (L1) and the control group (L0), and then fed with or without a basal diet containing L. reuteri ZJF036 (10⁹ CFU/g), respectively. The results showed that there was no significant difference in daily weight gain between the two groups (P > 0.05). However, we found that L. reuteri ZJF036 decreased Chao1 index and ACE index and increased the relative abundance of Firmicutes and Fusobacteria (P < 0.05) compared to the L0 group. In addition, we also found that the ratio of Firmicutes to Bacteroidetes was decreased in L1 group. Furthermore, the relative abundance of Lactobacillus increased, while that of Turicibacter and Blautia decreased in L1 group (P < 0.05). In conclusion, L. reuteri ZJF036 appeared to regulate the intestinal microbiota of beagle dogs. This study revealed the potential use of L. reuteri ZJBF036 as a probiotic supplement for beagle dogs.

Protective Effect of Lactiplantibacillus plantarum subsp. plantarum SC-5 on Dextran Sulfate Sodium-Induced Colitis in Mice

Inflammatory bowel disease (IBD) is a specific immune-associated intestinal disease. At present, the conventional treatment for patients is not ideal. Probiotics are widely used in the treatment of IBD patients due to their ability to restore the function of the intestinal mucosal barrier effectively and safely. Lactiplantibacillus plantarum subsp. plantarum is a kind of probiotic that exists in the intestines of hosts and is considered to have good probiotic properties. In this study, we evaluated the therapeutic effect of Lactiplantibacillus plantarum subsp. plantarum SC-5 (SC-5) on dextran sulfate sodium (DSS)-induced colitis in C57BL/6J mice. We estimated the effect of SC-5 on the clinical symptoms of mice through a body weight change, colon length, and DAI score. The inhibitory effects of SC-5 on the levels of cytokine IL-1β, IL-6, and TNF-α were determined by ELISA. The protein expression levels of NF-κB, MAPK signaling pathway, and the tight junction proteins occludin, claudin-3, and ZO-1 were verified using Western Blot and immunofluorescence. 16S rRNA was used to verify the modulatory effect of SC-5 on the structure of intestinal microbiota in DSS-induced colitis mice. The results showed that SC-5 could alleviate the clinical symptoms of DSS-induced colitis mice, and significantly reduce the expression of pro-inflammatory cytokines in the colon tissue. It also attenuated the inflammatory response by inhibiting the protein expression of NF-κB and MAPK signaling pathways. SC-5 improved the integrity of the intestinal mucosal barrier by strengthening tight junction proteins. In addition, 16S rRNA sequencing demonstrated that SC-5 was effective in restoring intestinal flora balance, as well as in increasing the relative abundance and diversity of beneficial microbiota. These results indicated that SC-5 has the potential to be developed as a new probiotic candidate that prevents or alleviates IBD.

Membrane vesicles released by Lacticaseibacillus casei BL23 inhibit the biofilm formation of Salmonella Enteritidis

Biofilms represent a major concern in the food industry and healthcare. The use of probiotic bacteria and their derivatives as an alternative to conventional treatments to fight biofilm development is a promising option that has provided convincing results in the last decades. Recently, membrane vesicles (MVs) produced by probiotics have generated considerable interest due to the diversity of roles they have been associated with. However, the antimicrobial activity of probiotic MVs remains to be studied. In this work, we showed that membrane vesicles produced by Lacticaseibacillus casei BL23 (LC-MVs) exhibited strong antibiofilm activity against Salmonella enterica serovar Enteritidis (S. Enteritidis) without affecting bacterial growth. Furthermore, we found that LC-MVs affected the early stages of S. Enteritidis biofilm development and prevented attachment of bacteria to polystyrene surfaces. Importantly, LC-MVs did not impact the biomass of already established biofilms. We also demonstrated that the antibiofilm activity depended on the proteins associated with the LC-MV fraction. Finally, two peptidoglycan hydrolases (PGHs) were found to be associated with the antibiofilm activity of LC-MVs. Overall, this work allowed to identify the antibiofilm properties of LC-MVs and paved the way for the use of probiotic MVs against the development of negative biofilms.

Effects of three different probiotics of Tibetan sheep origin and their complex probiotics on intestinal damage, immunity, and immune signaling pathways of mice infected with Clostridium perfringens type C

Tibetan sheep have unique intestinal microorganisms in their intestines that are adapted to the highland alpine and anoxic environment. To further clarify the probiotic properties of Tibetan sheep-derived probiotics, we selected three Tibetan sheep-derived probiotic isolates (Enterococcus faecalis EF1-mh, Bacillus subtilis BS1-ql, and Lactobacillus sakei LS-ql) to investigate the protective mechanisms of monocultures and their complex strains against Clostridium perfringens type C infection in mice. We established a model of C. perfringens type C infection and used histology and molecular biology to analyze the effects and mechanisms of different probiotic treatments on mice after C. perfringens type C infection. After supplementation with either probiotics or complex probiotics, mice were improved in terms of weight reduction and reduced the levels of cytokines in serum and increased the levels of intestinal sIgA, and supplementation with complex probiotics was effective. In addition, both probiotic and complex probiotic supplementation effectively improved the damage of intestinal mucosa and spleen tissue. The relative expressions of Muc 2, Claudin-1, and Occludin genes were increased in the ileum. The three probiotics and the compound probiotics treatment significantly reduced the relative mRNA expression of toll-like/MyD88/NF-κB/MAPK. The effect of probiotic treatment was similar to the results of engramycin treatment, but the effect of engramycin treatment on intestinal sIgA was not significant. Our results clarify the immunomodulatory effects of the three probiotic isolates and the complex probiotics on C. perfringens infection, and the repair of the intestinal mucosal barrier.

Journey of the Probiotic Bacteria: Survival of the Fittest

This review aims to bring a more general view of the technological and biological challenges regarding production and use of probiotic bacteria in promoting human health. After a brief description of the current concepts, the challenges for the production at an industrial level are presented from the physiology of the central metabolism to the ability to face the main forms of stress in the industrial process. Once produced, these cells are processed to be commercialized in suspension or dried forms or added to food matrices. At this stage, the maintenance of cell viability and vitality is of paramount for the quality of the product. Powder products requires the development of strategies that ensure the integrity of components and cellular functions that allow complete recovery of cells at the time of consumption. Finally, once consumed, probiotic cells must face a very powerful set of physicochemical mechanisms within the body, which include enzymes, antibacterial molecules and sudden changes in pH. Understanding the action of these agents and the induction of cellular tolerance mechanisms is fundamental for the selection of increasingly efficient strains in order to survive from production to colonization of the intestinal tract and to promote the desired health benefits.

Effect of Lactobacillus reuteri S5 Intervention on Intestinal Microbiota Composition of Chickens Challenged with Salmonella enteritidis

To understand the mechanism of lactic acid bacteria against Salmonella enteritidis infection; we examined how lactic acid bacteria regulated the intestinal microbiota to resist infection by pathogenic bacteria. The probiotic strain Lactobacillus reuteri S5 was used to construct an animal model of S. enteritidis infected broilers. A high-throughput sequencing technology was used to analyze the regulatory effects of L. reuteri S5 on the structure of the intestinal microbiota of broilers infected with S. enteritidis; and to examine the possible defense mechanism they used. Our results showed that the administration of L. reuteri S5 reduced colonization of S. enteritidis (p < 0.05), decreased intestinal permeability (p < 0.05), and reduced the bacterial displacement likely due by S. enteritidis colonization (p < 0.05), suggesting some enhancement of the intestinal barrier function. Furthermore, L. reuteri S5 increased the number of operational taxonomic units (OTUs) in the chicken cecal microflora and the relative abundance of Lactobacillaceae and decreased the relative abundance of Enterobacteriaceae. These results suggest that the lactic acid bacterium L. reuteri S5 protected the intestinal microbiota of chickens against S. enteritidis infection.

Antagonistic activity and mechanism of Lactobacillus rhamnosus SQ511 against Salmonella enteritidis

Salmonella enteritidis is an important food-borne pathogen. The use of antibiotics is a serious threat to animal and human health, owing to the existence of resistant strains and drug residues. Lactic acid bacteria, as a new alternative to antibiotics, has attracted much attention. In this study, we investigated the antibacterial potential and underlying mechanism of Lactobacillus rhamnosus SQ511 against S. enteritidis ATCC13076. The results revealed that L. rhamnosus SQ511 significantly inhibited S. enteritidis ATCC13076 growth or even caused death. Laser confocal microscopic imaging revealed that the cell-free supernatant (CFS) of L. rhamnosus SQ511 elevated the reactive oxygen species level and bacterial membrane depolarization in S. enteritidis ATCC13076, leading to cell death. Furthermore, L. rhamnosus SQ511 CFS had severely deleterious effects on S. enteritidis ATCC13076, causing membrane destruction and the release of cellular materials. In addition, L. rhamnosus SQ511 CFS significantly reduced the expression of virulence, motility, adhesion, and invasion genes in S. enteritidis ATCC13076 (P < 0.05), and considerably inhibited motility and biofilm formation capacity (P < 0.05). Thus, antimicrobial compounds produced by L. rhamnosus SQ511 strongly inhibited S. enteritidis growth, mobility, biofilm formation, membrane disruption, and reactive oxygen species generation, and regulated virulence-related gene expressions, presenting promising applications as a probiotic agent.

Biological characteristics and whole-genome analysis of the potential probiotic, Lactobacillus reuteri S5

Lactic acid bacteria are microorganisms used for probiotic purposes and form major parts of human and mammalian intestinal microbiota, exerting important health-promoting effects on the host. Here, we evaluated L. reuteri strain S5 isolated from the intestines of healthy white feather broilers. L. reuteri S5 grew best after 20 h of incubation in MRS medium. Lactic acid production was 1.42 mmol L^-1 at 24 h, which was well tolerated. Activities of T-AOC, GSH-Px and T-SOD in the cell-free fermentation supernatant of L. reuteri S5 were higher than those in the bacteria, and the strain showed good hydrophobicity in vitro. The dominant carbon and nitrogen sources of L. reuteri S5 were glucose and soybean meal. A high-quality complete genome map of L. reuteri S5 was obtained using a Pacbio nanopore third-generation sequencing platform. The results showed that L. reuteri S5 possesses a complete primary metabolic pathway, encoding the main functional enzymes of the glycolysis pathway and pentose phosphate pathway. The genome contains genes encoding antioxidants and conferring tolerance to inorganic salt ions, acids and bile salts. This study shows that L. reuteri S5 is a probiotic strain with excellent probiotic characteristics and has great potential for the development of feed additives to promote animal health.

Research progress on the regulation mechanism of probiotics on the microecological flora of infected intestines in livestock and poultry

The animal intestine is a complex ecosystem composed of host cells, gut microbiota and available nutrients. Gut microbiota can prevent the occurrence of intestinal diseases in animals by regulating the homeostasis of the intestinal environment. The intestinal microbiota is a complex and stable microbial community, and the homeostasis of the intestinal environment is closely related to the invasion of intestinal pathogens, which plays an important role in protecting the host from pathogen infections. Probiotics are strains of microorganisms that are beneficial to health, and their potential has recently led to a significant increase in studies on the regulation of intestinal flora. Various potential mechanisms of action have been proposed on probiotics, especially mediating the regulation mechanism of the intestinal flora on the host, mainly including competitive inhibition of pathogens, stimulation of the host's adaptive immune system and regulation of the intestinal flora. The advent of high-throughput sequencing technology has given us a clearer understanding and has facilitated the development of research methods to investigate the intestinal microecological flora. This review will focus on the regulation of probiotics on the microbial flora of intestinal infections in livestock and poultry and will depict future research directions.

Lactobacillus reuteri and Enterococcus faecium from Poultry Gut Reduce Mucin Adhesion and Biofilm Formation of Cephalosporin and Fluoroquinolone-Resistant Salmonella enterica

Non-typhoidal Salmonella (NTS) can cause infection in poultry, livestock, and humans. Although the use of antimicrobials as feed additives is prohibited, the previous indiscriminate use and poor regulatory oversight in some parts of the world have resulted in increased bacterial resistance to antimicrobials, including cephalosporins and fluoroquinolones, which are among the limited treatment options available against NTS. This study aimed to isolate potential probiotic lactic acid bacteria (LAB) strains from the poultry gut to inhibit fluoroquinolone and cephalosporin resistant MDR Salmonella Typhimurium and S. Enteritidis. The safety profile of the LAB isolates was evaluated for the hemolytic activity, DNase activity, and antibiotic resistance. Based on the safety results, three possible probiotic LAB candidates for in vitro Salmonella control were chosen. Candidate LAB isolates were identified by 16S rDNA sequencing as Lactobacillus reuteri PFS4, Enterococcus faecium PFS13, and Enterococcus faecium PFS14. These strains demonstrated a good tolerance to gastrointestinal-related stresses, including gastric acid, bile, lysozyme, and phenol. In addition, the isolates that were able to auto aggregate had the ability to co-aggregate with MDR S. Typhimurium and S. Enteritidis. Furthermore, LAB strains competitively reduced the adhesion of pathogens to porcine mucin Type III in co-culture studies. The probiotic combination of the selected LAB isolates inhibited the biofilm formation of S. Typhimurium FML15 and S. Enteritidis FML18 by 90% and 92%, respectively. In addition, the cell-free supernatant (CFS) of the LAB culture significantly reduced the growth of Salmonella in vitro. Thus, L. reuteri PFS4, E. faecium PFS13, and E. faecium PFS 14 are potential probiotics that could be used to control MDR S. Typhimurium and S. Enteritidis in poultry. Future investigations are required to elucidate the in vivo potential of these probiotic candidates as Salmonella control agents in poultry and animal feed.

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

Acute non-typhoidal salmonellosis (NTS) caused by Salmonella enterica Typhimurium (STM) is among the most prevalent of foodborne diseases. A global rising of antibiotic resistance strains of STM raises an urgent need for alternative methods to control this important pathogen. Major human food animals which harbor STM in their gut are cattle, swine, and poultry. Previous studies showed that the probiotic Limosilactobacillus (Lactobacillus) reuteri KUB-AC5 (AC5) exhibited anti-Salmonella activities in chicken by modulating gut microbiota and the immune response. However, the immunobiotic effect of AC5 in a mammalian host is still not known. Here, we investigated the anti-Salmonella and anti-inflammatory effects of AC5 on STM infection using a mouse colitis model. Three groups of C57BL/6 mice (prophylactic, therapeutic, and combined) were fed with 10⁹ colony-forming units (cfu) AC5 daily for 7, 4, and 11 days, respectively. Then, the mice were challenged with STM compared to the untreated group. By using a specific primer pair, we found that AC5 can transiently colonize mouse gut (colon, cecum, and ileum). Interestingly, AC5 reduced STM gut proliferation and invasion together with attenuated gut inflammation and systemic dissemination in mice. The decreased STM numbers in mouse gut lumen, gut tissues, and spleen possibly came from longer AC5 feeding duration and/or the combinatorial (direct and indirect inhibitory) effect of AC5 on STM. However, AC5 attenuated inflammation (both in the gut and in the spleen) with no difference between these three approaches. This study demonstrated that AC5 confers both direct and indirect inhibitory effects on STM in the inflamed gut.

Evaluation of the probiotic and functional potential of Lactobacillus agilis 32 isolated from pig manure

Escherichia coli is a symbiotic bacterium in humans and animals and an important pathogen of humans and animals. Prevention and suppression of E. coli infection is of great concern. In this study, we isolated a strain of Lactobacillus agilis 32 from pig manure and evaluated its biological characteristics, and found that its bacterial survival rate was 25% after 4 h of treatment at pH 2, and under the condition of 0·5% bile concentration, its survival rate exceeds 30%. In addition, L. agilis 32 has a cell surface hydrophobicity of 77·8%, and exhibits 67·1% auto-aggregation and 63·2% aggregation with Enterotoxigenic E. coli 10 (ETEC 10). FITC fluorescence labelling showed that the fluorescence intensity of cecum was significantly higher than that of duodenum, jejunum or colon (P < 0·05), but no significant difference from ileum. Lactobacillus agilis 32 bacterial culture and CFS showed average inhibition zone diameters of 14·2 and 15·4 mm respectively. Lactobacillus agilis 32 CFS treatment can significantly reduce the pathogenicity of ETEC 10. These results show that L. agilis 32 is an active and potential probiotic, and it has a good antibacterial effect on ETEC10, which provides basic research for probiotics to prevent and treat intestinal diarrhoea pathogen infection.

Bacillus subtilis and lactic acid bacteria improve the growth performance and blood parameters and reduce Salmonella infection in broilers

Aim

The aim of the study was to determine the potentials and effects of Bacillus subtilis and lactic acid bacteria (LAB) as probiotics on broiler growth, health, and Salmonella infection.

Materials and Methods

To evaluate the inoculum size applicable for broilers, 1-day-old broilers were orally fed fresh cultures of single strains and a B. subtilis KKU213/Pediococcus pentosaceus NP6 mixture at 10⁸ and 10¹² colony-forming unit (CFUs)/mL/chick. The body weight gain (BWG), Salmonella contamination level and total Bacillus and LAB abundances in the crop and intestine were measured. Subsequently, 1-day-old broilers were orally fed of KKU213, CH403, and Pediococcus acidilactici SH8 at 10¹⁰ CFUs/mL, followed by inulin. After 35 days, the BWG, Bacillus and LAB abundances in the cecum, blood parameters, and KKU213 colonization were assessed.

Results

The broilers fed single strains or KKU213+NP6 exhibited a higher BWG and a higher crop LAB abundance than the controls (p<0.05). Probiotic feeding decreased the intestinal Salmonella abundance and correspondingly increased the LAB abundance. The broilers fed the mixed culture (KKU213+CH403+SH8) followed by prebiotics showed lower mortality, higher blood high-density lipoprotein levels, and lower blood uric acid levels than the controls (p<0.0004). Probiotic feeding significantly increased the Bacillus and LAB counts (p<0.05). A CE330 isolate obtained from the cecum after 35 days of KKU213 feeding was closely related to B. subtilis KKU213.

Conclusion

B. subtilis KKU213 is a potent probiotic strain that can survive, colonize and reduce Salmonella infection in broilers and improve their growth and health. This strain, combined with different LAB can act synergistically in the gut and promote broiler growth.