Colonization of Germ-Free Piglets with Commensal Lactobacillus amylovorus, Lactobacillus mucosae, and Probiotic E. coli Nissle 1917 and Their Interference with Salmonella Typhimurium

Priority order of neonatal colonization by a probiotic or pathogenic Escherichia coli strain dictates the host response to experimental colitis

The alarming prevalence of inflammatory bowel disease (IBD) in early childhood is associated with imbalances in the microbiome, the immune response, and environmental factors. Some pathogenic Escherichia coli (E. coli) strains have been found in IBD patients, where they may influence disease progression. Therefore, the discovery of new harmful bacterial strains that have the potential to drive the inflammatory response is of great importance. In this study, we compared the immunomodulatory properties of two E. coli strains of serotype O6: the probiotic E. coli Nissle 1917 and the uropathogenic E. coli O6:K13:H1. Using the epithelial Caco-2 cell line, we investigated the different abilities of the strains to adhere to and invade epithelial cells. We confirmed the potential of E. coli Nissle 1917 to modulate the Th1 immune response in a specific manner in an in vitro setting by stimulating mouse bone marrow-derived dendritic cells (BM-DCs). In gnotobiotic in vivo experiments, we demonstrated that neonatal colonization with E. coli Nissle 1917 achieves a stable high concentration in the intestine and protects mice from the progressive effect of E. coli O6:K13:H1 in developing ulcerative colitis in an experimental model. In contrast, a single-dose treatment with E. coli Nissle 1917 is ineffective in achieving such high concentrations and does not protect against DSS-induced ulcerative colitis in mice neonatally colonized with pathobiont E. coli O6:K13:H1. Despite the stable coexistence of both E. coli strains in the intestinal environment of the mice, we demonstrated a beneficial competitive interaction between the early colonizing E. coli Nissle 1917 and the late-arriving strain O6:K13:H1, suggesting its anti-inflammatory potential for the host. This study highlights the importance of the sequence of bacterial colonization, which influences the development of the immune response in the host gut and potentially impacts future quality of life.

Role of immunomodulatory probiotics in alleviating bacterial diarrhea in piglets: a systematic review

Diarrhea is a common enteric disease in piglets that leads to high mortality and economic losses in swine production worldwide. Antibiotics are commonly used to prevent or treat diarrhea in piglets. However, irrational antibiotic use contributes to the development of resistance in bacteria and antibiotic residues in animal products, threatening public health, while causing gut microbiota dysbiosis and antibiotic-resistant bacterial infection in piglets. Therefore, the quest for alternative products (such as probiotics, prebiotics, organic acids, enzymes, essential oils, medium-chain fatty acids, zinc, and plant extracts) has recently been clearly emphasized through the increase in regulations regarding antibiotic use in livestock production. These antibiotic alternatives could lower the risk of antibiotic-resistant bacteria and meet consumer demand for antibiotic-free food. Several antibiotic alternatives have been proposed, including immunomodulatory probiotics, as candidates to reduce the need for antimicrobial therapy. Many studies have revealed that probiotics can avert and cure bacterial diarrhea by regulating the gut function and immune system of piglets. In this review, we focus on the major pathogenic bacteria causing piglet diarrhea, the research status of using probiotics to prevent and treat diarrhea, their possible mechanisms, and the safety issues related to the use of probiotics. Supplementation with probiotics is a possible alternative to antibiotics for the prevention or treatment of bacterial diarrhea in piglets. Furthermore, probiotics exert beneficial effects on feed efficiency and growth performance of piglets. Therefore, appropriate selection and strategies for the use of probiotics may have a positive effect on growth performance and also reduce diarrhea in piglets. This review provides useful information on probiotics for researchers, pig nutritionists, and the additive industry to support their use against bacterial diarrhea in piglets.

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.

Commensal Bacteria Impact on Intestinal Toll-like Receptor Signaling in Salmonella-Challenged Gnotobiotic Piglets

Gnotobiotic (GN) animals with simple and defined microbiota can help to elucidate host-pathogen interferences. Hysterectomy-derived germ-free (GF) minipigs were associated at 4 and 24 h post-hysterectomy with porcine commensal mucinolytic Bifidobacterium boum RP36 (RP36) strain or non-mucinolytic strain RP37 (RP37) or at 4 h post-hysterectomy with Lactobacillus amylovorus (LA). One-week-old GN minipigs were infected with Salmonella Typhimurium LT2 strain (LT2). We monitored histological changes in the ileum, mRNA expression of Toll-like receptors (TLRs) 2, 4, and 9 and their related molecules lipopolysaccharide-binding protein (LBP), coreceptors MD-2 and CD14, adaptor proteins MyD88 and TRIF, and receptor for advanced glycation end products (RAGE) in the ileum and colon. LT2 significantly induced expression of TLR2, TLR4, MyD88, LBP, MD-2, and CD14 in the ileum and TLR4, MyD88, TRIF, LBP, and CD14 in the colon. The LT2 infection also significantly increased plasmatic levels of inflammatory markers interleukin (IL)-6 and IL-12/23p40. The previous colonization with RP37 alleviated damage of the ileum caused by the Salmonella infection, and RP37 and LA downregulated plasmatic levels of IL-6. A defined oligo-microbiota composed of bacterial species with selected properties should probably be more effective in downregulating inflammatory response than single bacteria.

The Effect of Maternal Probiotic or Synbiotic Supplementation on Sow and Offspring Gastrointestinal Microbiota, Health, and Performance

The increasing prevalence of antimicrobial-resistant pathogens has prompted the reduction in antibiotic and antimicrobial use in commercial pig production. This has led to increased research efforts to identify alternative dietary interventions to support the health and development of the pig. The crucial role of the GIT microbiota in animal health and performance is becoming increasingly evident. Hence, promoting an improved GIT microbiota, particularly the pioneer microbiota in the young pig, is a fundamental focus. Recent research has indicated that the sow's GIT microbiota is a significant contributor to the development of the offspring's microbiota. Thus, dietary manipulation of the sow's microbiota with probiotics or synbiotics, before farrowing and during lactation, is a compelling area of exploration. This review aims to identify the potential health benefits of maternal probiotic or synbiotic supplementation to both the sow and her offspring and to explore their possible modes of action. Finally, the results of maternal sow probiotic and synbiotic supplementation studies are collated and summarized. Maternal probiotic or synbiotic supplementation offers an effective strategy to modulate the sow's microbiota and thereby enhance the formation of a health-promoting pioneer microbiota in the offspring. In addition, this strategy can potentially reduce oxidative stress and inflammation in the sow and her offspring, enhance the immune potential of the milk, the immune system development in the offspring, and the sow's feed intake during lactation. Although many studies have used probiotics in the maternal sow diet, the most effective probiotic or probiotic blends remain unclear. To this extent, further direct comparative investigations using different probiotics are warranted to advance the current understanding in this area. Moreover, the number of investigations supplementing synbiotics in the maternal sow diet is limited and is an area where further exploration is warranted.

Effects of stimbiotic supplementation on gut health, immune response, and intestinal microbiota in weaned piglets challenged with E. coli

In order to make piglet diets more effective, it is necessary to investigate effective methods for breaking down xylan in cereal. The objective of this study was to determine the effects of dietary stimbiotic (STB) supplementation on growth performance, intestinal morphology, immune response and intestinal microbiota in weaned piglets. A total of 24 (Duroc × Yorkshire × Landrace) weaned pigs (initial body weight of 8.01 ± 0.38 kg and 28 ± 3 d old), were assigned to 4 treatments with 6 replicates per treatment. Pigs were housed in individual pens for 17 days, including 5 days adaption period and 12 days after the first Escherichia coli (E. coli) challenge. The experiment was conducted in a 2 × 2 factorial arrangement of treatments consisting of two levels of challenge (challenge and non-challenge) and two levels of STB (0 and 0.5 g/kg diet). Supplementations of STB 0.5 g/kg improved the gain to feed ratio (G:F) (P < 0.05) in piglets challenged with shiga toxigenic E. coli (STEC). STB supplementation decreased (P < 0.05) white blood cells, neutrophils, lymphocytes, and expression levels of tumor necrosis factor-alpha and interleukin-6. Supplementation of STB improved (P < 0.05) the lymphocytes and neutrophils in piglets challenged with STEC on 12 dpi. Supplementation of STB also improved (P < 0.05) the villus height to-crypt depth ratio of ileum in piglets challenged with STEC. Supplementation of STB increased (P < 0.05) the expression levels of claudin-1 of ileum. In genus level, supplementation of STB increased (P < 0.001) the abundance of Prevotella compared to non-supplementation of STB groups in pre-inoculation period. Also, supplementation of STB decreased (P < 0.05) the abundance of Faecalibacterium and Eubacterium_coprostanoligenes_group compared to non-supplementation of STB groups in post-inoculation period. In phylum level, supplementation of STB increased (P < 0.05) the abundance of Desulfobacterota and Fibrobacterota in pre-inoculation period. E. coli challenge increased the abundance of Fibrobacterota compared to non-challenged group in post-inoculation period. In conclusion, these findings indicated that STB supplementation could alleviate a decrease of the performance, immune response, and inflammatory response in piglets induced by the STEC challenge.

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.

Microcins reveal natural mechanisms of bacterial manipulation to inform therapeutic development

Microcins are an understudied and poorly characterized class of antimicrobial peptides. Despite the existence of only 15 examples, all identified from the Enterobacteriaceae, microcins display diversity in sequence, structure, target cell uptake, cytotoxic mechanism of action and target specificity. Collectively, these features describe some of the unique means nature has contrived for molecules to cross the 'impermeable' barrier of the Gram-negative bacterial outer membrane and inflict cytotoxic effects. Microcins appear to be widely dispersed among different species and in different environments, where they function in regulating microbial communities in diverse ways, including through competition. Growing evidence suggests that microcins may be adapted for therapeutic uses such as antimicrobial drugs, microbiome modulators or facilitators of peptide uptake into cells. Advancing our biological, ecological and biochemical understanding of the roles of microcins in bacterial interactions, and learning how to regulate and modify microcin activity, is essential to enable such therapeutic applications.

Bacillus-Based Direct-Fed Microbial Reduces the Pathogenic Synergy of a Coinfection with Salmonella enterica Serovar Choleraesuis and Porcine Reproductive and Respiratory Syndrome Virus

Viral respiratory infections predispose lungs to bacterial coinfections causing a worse outcome than either infection alone. Porcine reproductive and respiratory syndrome virus (PRRSV) causes pneumonia in pigs and is often associated with bacterial coinfections. We examined the impact of providing weanling pigs a Bacillus-based direct-fed microbial (DFM) on the syndrome resulting from infection with either Salmonella enterica serotype Choleraesuis alone, or in combination with PRRSV. Nine days after the bacterial challenge, Salmonella was isolated from ileocecal lymph nodes of all challenged pigs regardless of DFM treatment. Compared to the single bacterial challenge, the dual challenge with Salmonella and PRRSV resulted in a pathogenic synergy exhibited by a higher rate of Salmonella colonization in the lung and a more extensive and severe interstitial pneumonia. Provision of DFM to dually challenged pigs reduced the rate of lung colonization by Salmonella, eliminated or reduced the presence of PRRSV in the lung, and reduced the extent and severity of gross lung pathology. Dually challenged pigs that received DFM had increased concentrations of interleukin 1 (IL-1) and IL-8 in lung lavage fluids, accompanied by increased expression in their blood cells of nucleotide-binding oligomerization domain receptor 2 (NOD2) and triggering receptor expressed in myeloid cells 1 (TREM-1) molecules. These changes in pulmonary inflammatory cytokine production and increased expression of NOD2 and TREM-1 suggest that the DFM exerted a systemic modulating effect on innate immunity. These observations are consistent with the notion that tonic stimulation by gut-derived microbial products can poise innate immunity to fight infections in the respiratory tract.

Haemonchus contortus Infection Alters Gastrointestinal Microbial Community Composition, Protein Digestion and Amino Acid Allocations in Lambs

The objective of this study was to investigate associations between gastrointestinal microbiota and protein metabolism of lambs infected with Haemonchus contortus. Sixteen male Ujumqin lambs (initial body weight = 32.4 ± 3.9 kg) were dewormed and randomly assigned to 2 equal groups, to be infected or not infected with Haemonchus contortus (GIN and CON, respectively). The experiment lasted 77 days. The GIN lambs had lower packed cell volume (PCV) and increased wormegg count (WEC) after 14 days. Furthermore, in infected lambs, there were decreases in apparent digestibility of dry matter (P = 0.011), crude protein (P = 0.004) and ether extract (P = 0.007), as well as decreased ruminal pepsin (P < 0.001) and lipase (P = 0.032) activity but increased ruminal α-amylase (P = 0.004) and cellulase activity (P = 0.002), and decreased jejunal α-amylase activity (P = 0.033). In addition, infection with H. contortus decreased alpha diversity of the gastrointestinal microbial community in the rumen, abomasum and duodenum, although microbiota associated with carbohydrate and proteolytic metabolism were increased and up to 32 KEGG pathways in the duodenum were predicted to be significantly affected. In conclusion, H. contortus infection in lambs altered the gastrointestinal microbial community composition and disturbed protein digestion and allocation of absorbed amino acids. These results provided insights into consequences of H. contortus infection in lambs and could facilitate development of novel nutritional strategies to improve animal health.

Innovative Treatments Enhancing the Functionality of Gut Microbiota to Improve Quality and Microbiological Safety of Foods of Animal Origin

The gastrointestinal tract, or gut, microbiota is a microbial community containing a variety of microorganisms colonizing throughout the gut that plays a crucial role in animal health, growth performance, and welfare. The gut microbiota is closely associated with the quality and microbiological safety of foods and food products originating from animals. The gut microbiota of the host can be modulated and enhanced in ways that improve the quality and safety of foods of animal origin. Probiotics—also known as direct-fed microbials—competitive exclusion cultures, prebiotics, and synbiotics have been utilized to achieve this goal. Reducing foodborne pathogen colonization in the gut prior to slaughter and enhancing the chemical, nutritional, or sensory characteristics of foods (e.g., meat, milk, and eggs) are two of many positive outcomes derived from the use of these competitive enhancement–based treatments in food-producing animals.

Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Lactobacillus casei Zhang Counteracts Blood-Milk Barrier Disruption and Moderates the Inflammatory Response in Escherichia coli-Induced Mastitis

Escherichia coli is a common mastitis-causing pathogen that can disrupt the blood-milk barrier of mammals. Although Lactobacillus casei Zhang (LCZ) can alleviate mice mastitis, whether it has a prophylactic effect on E. coli-induced mastitis through intramammary infusion, as well as its underlying mechanism, remains unclear. In this study, E. coli-induced injury models of bovine mammary epithelial cells (BMECs) and mice in lactation were used to fill this research gap. In vitro tests of BMECs revealed that LCZ significantly inhibited the E. coli adhesion (p < 0.01); reduced the cell desmosome damage; increased the expression of the tight junction proteins claudin-1, claudin-4, occludin, and zonula occludens-1 (ZO-1; p < 0.01); and decreased the expression of the inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 (p < 0.01), thereby increasing trans-epithelial electric resistance (p < 0.01) and attenuating the lactate dehydrogenase release induced by E. coli (p < 0.01). In vivo tests indicated that LCZ significantly reduced the injury and histological score of mice mammary tissues in E. coli-induced mastitis (p < 0.01) by significantly promoting the expression of the tight junction proteins claudin-3, occludin, and ZO-1 (p < 0.01), which ameliorated blood-milk barrier disruption, and decreasing the expression of the inflammatory cytokines (TNF-α, IL-1β, and IL-6) in mice mammary tissue (p < 0.01). Our study suggested that LCZ counteracted the disrupted blood-milk barrier and moderated the inflammatory response in E. coli-induced injury models, indicating that LCZ can ameliorate the injury of mammary tissue in mastitis.

Monoassociation of Preterm Germ-Free Piglets with Bifidobacterium animalis Subsp. lactis BB-12 and Its Impact on Infection with Salmonella Typhimurium

Preterm germ-free piglets were monoassociated with probiotic Bifidobacterium animalis subsp. lactis BB-12 (BB12) to verify its safety and to investigate possible protection against subsequent infection with Salmonella Typhimurium strain LT2 (LT2). Clinical signs of salmonellosis, bacterial colonization in the intestine, bacterial translocation to mesenteric lymph nodes (MLN), blood, liver, spleen, and lungs, histopathological changes in the ileum, claudin-1 and occludin mRNA expression in the ileum and colon, intestinal and plasma concentrations of IL-8, TNF-α, and IL-10 were evaluated. Both BB12 and LT2 colonized the intestine of the monoassociated piglets. BB12 did not translocate in the BB12-monoassociated piglets. BB12 was detected in some cases in the MLN of piglets, consequently infected with LT2, but reduced LT2 counts in the ileum and liver of these piglets. LT2 damaged the luminal structure of the ileum, but a previous association with BB12 mildly alleviated these changes. LT2 infection upregulated claudin-1 mRNA in the ileum and colon and downregulated occludin mRNA in the colon. Infection with LT2 increased levels of IL-8, TNF-α, and IL-10 in the intestine and plasma, and BB12 mildly downregulated them compared to LT2 alone. Despite reductions in bacterial translocation and inflammatory cytokines, clinical signs of LT2 infection were not significantly affected by the probiotic BB12. Thus, we hypothesize that multistrain bacterial colonization of preterm gnotobiotic piglets may be needed to enhance the protective effect against the infection with S. Typhimurium LT2.

Colonization of Germ-Free Piglets with Mucinolytic and Non-Mucinolytic Bifidobacterium boum Strains Isolated from the Intestine of Wild Boar and Their Interference with Salmonella Typhimurium

Non-typhoidal Salmonella serovars are worldwide spread foodborne pathogens that cause diarrhea in humans and animals. Colonization of gnotobiotic piglet intestine with porcine indigenous mucinolytic Bifidobacterium boum RP36 strain and non-mucinolytic strain RP37 and their interference with Salmonella Typhimurium infection were compared. Bacterial interferences and impact on the host were evaluated by clinical signs of salmonellosis, bacterial translocation, goblet cell count, mRNA expression of mucin 2, villin, claudin-1, claudin-2, and occludin in the ileum and colon, and plasmatic levels of inflammatory cytokines IL-8, TNF-α, and IL-10. Both bifidobacterial strains colonized the intestine comparably. Neither RP36 nor RP37 B. boum strains effectively suppressed signs of salmonellosis. Both B. boum strains suppressed the growth of S. Typhimurium in the ileum and colon. The mucinolytic RP36 strain increased the translocation of S. Typhimurium into the blood, liver, and spleen.

High Mobility Group Box 1 and TLR4 Signaling Pathway in Gnotobiotic Piglets Colonized/Infected with L. amylovorus, L. mucosae, E. coli Nissle 1917 and S. Typhimurium

High mobility group box 1 (HMGB1) is a DNA-binding nuclear protein that can be actively secreted by immune cells after different immune stimuli or passively released from cells undergoing necrosis. HMGB1 amplifies inflammation, and its hypersecretion contributes to multiple organ dysfunction syndrome and death. We tested possible immunomodulatory effect of commensal Lactobacillus amylovorus (LA), Lactobacillus mucosae (LM) or probiotic Escherichia coli Nissle 1917 (EcN) in infection of gnotobiotic piglets with Salmonella Typhimurium (ST). Transcription of HMGB1 and Toll-like receptors (TLR) 2, 4, and 9 and receptor for advanced glycation end products (RAGE), TLR4-related molecules (MD-2, CD14, and LBP), and adaptor proteins (MyD88 and TRIF) in the ileum and colon were measured by RT-qPCR. Expression of TLR4 and its related molecules were highly upregulated in the ST-infected intestine, which was suppressed by EcN, but not LA nor LM. In contrast, HMGB1 expression was unaffected by ST infection or commensal/probiotic administration. HMGB1 protein levels in the intestine measured by ELISA were increased in ST-infected piglets, but they were decreased by previous colonization with E. coli Nissle 1917 only. We conclude that the stability of HMGB1 mRNA expression in all piglet groups could show its importance for DNA transcription and physiological cell functions. The presence of HMGB1 protein in the intestinal lumen probably indicates cellular damage.