The role of intestinal volatile fatty acids in the Salmonella shedding of pigs

Cold Exposure during the Active Phase Affects the Short-Chain Fatty Acid Production of Mice in a Time-Specific Manner

Chronic or acute ambient temperature change alter the gut microbiota and the metabolites, regulating metabolic functions. Short-chain fatty acids (SCFAs) produced by gut bacteria reduce the risk of disease. Feeding patterns and gut microbiota that are involved in SCFAs production are controlled by the circadian clock. Hence, the effect of environmental temperature change on SCFAs production is expected depending on the exposure timing. In addition, there is limited research on effects of habitual cold exposure on the gut microbiota and SCFAs production compared to chronic or acute exposure. Therefore, the aim was to examine the effect of cold or heat exposure timing on SCFAs production. After exposing mice to 7 or 37 °C for 3 h a day at each point for 10 days, samples were collected, and cecal pH, SCFA concentration, and BAT weight was measured. As a result, cold exposure at ZT18 increased cecal pH and decreased SCFAs. Intestinal peristalsis was suppressed due to the cold exposure at ZT18. The results reveal differing effects of intermittent cold exposure on the gut environment depending on exposure timing. In particular, ZT18 (active phase) is the timing to be the most detrimental to the gut environment of mice.

Culturable micro-organisms in human milk were found to be associated with maternal weight, diet and age during early lactation

AIMS

This study aimed to evaluate the influence of maternal factors on the total plate count, Staphylococci, Lactobacilli and Bifidobacteria populations in the milk of lactating Filipino women for the first 4 months of lactation period.

METHODS AND RESULTS

Milk samples (n = 136), 24 h diet recalls and responses from a qualitative food frequency questionnaire (FFQ) were collected from 34 healthy lactating women classified according to their BMI: underweight (n = 7), normal weight (n = 16) and overweight (n = 11). The FFQ was useful in assessing prebiotic and probiotic food items consumed by the participants. Microbial populations were enumerated using culture-plating method, and showed a nonsignificant decreasing trend suggesting their relative stability throughout the first 4 months of lactation. Carbohydrate and fat intakes were associated with TPC, and with both TPC and Staphylococci respectively (P ≤ 0·05); and consumption of root crop is linked with Staphylococci, Lactobacilli and Bifidobacteria (P ≤ 0·05). Interestingly, age was found to be a positive determinant for Bifidobacteria (P = 0·00), whereas being normal- or overweight as negative determinants of Lactobacilli (P = 0·017). Consumption of milk also seems to positively influence both Lactobacilli (P = 0·00) and Bifidobacteria (P = 0·05) counts.

CONCLUSIONS

Certain populations of culturable micro-organisms were found to be associated with maternal diet, weight classification and age.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study offered new discoveries in the recently growing endeavor on the role of maternal factors in modulating certain microbial populations in human milk. Ultimately, the findings of this study could provide a basis in crafting lactation policies and guidelines that may help enhance the microbial quality of human milk through adjustments in maternal diet or weight during lactation.

Oncobiosis and Microbial Metabolite Signaling in Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is one of the most lethal cancers in both men and women, with a median five-year survival of around 5%. Therefore, pancreatic adenocarcinoma represents an unmet medical need. Neoplastic diseases, such as pancreatic adenocarcinoma, often are associated with microbiome dysbiosis, termed oncobiosis. In pancreatic adenocarcinoma, the oral, duodenal, ductal, and fecal microbiome become dysbiotic. Furthermore, the pancreas frequently becomes colonized (by Helicobacter pylori and Malassezia, among others). The oncobiomes from long- and short-term survivors of pancreatic adenocarcinoma are different and transplantation of the microbiome from long-term survivors into animal models of pancreatic adenocarcinoma prolongs survival. The oncobiome in pancreatic adenocarcinoma modulates the inflammatory processes that drive carcinogenesis. In this review, we point out that bacterial metabolites (short chain fatty acids, secondary bile acids, polyamines, indole-derivatives, etc.) also have a role in the microbiome-driven pathogenesis of pancreatic adenocarcinoma. Finally, we show that bacterial metabolism and the bacterial metabolome is largely dysregulated in pancreatic adenocarcinoma. The pathogenic role of additional metabolites and metabolic pathways will be identified in the near future, widening the scope of this therapeutically and diagnostically exploitable pathogenic pathway in pancreatic adenocarcinoma.

Microbial Metabolites Determine Host Health and the Status of Some Diseases

The gastrointestinal (GI) tract is a highly complex organ composed of the intestinal epithelium layer, intestinal microbiota, and local immune system. Intestinal microbiota residing in the GI tract engages in a mutualistic relationship with the host. Different sections of the GI tract contain distinct proportions of the intestinal microbiota, resulting in the presence of unique bacterial products in each GI section. The intestinal microbiota converts ingested nutrients into metabolites that target either the intestinal microbiota population or host cells. Metabolites act as messengers of information between the intestinal microbiota and host cells. The intestinal microbiota composition and resulting metabolites thus impact host development, health, and pathogenesis. Many recent studies have focused on modulation of the gut microbiota and their metabolites to improve host health and prevent or treat diseases. In this review, we focus on the production of microbial metabolites, their biological impact on the intestinal microbiota composition and host cells, and the effect of microbial metabolites that contribute to improvements in inflammatory bowel diseases and metabolic diseases. Understanding the role of microbial metabolites in protection against disease might offer an intriguing approach to regulate disease.

Gastric infusion of short-chain fatty acids can improve intestinal barrier function in weaned piglets

Background

The present study was conducted to investigate the effects of gastric infusion of short-chain fatty acids (SCFA) on gut barrier function in a pig model. In this study, 21 DLY barrows with an average initial body weight of (8.31 ± 0.72) kg were randomly allotted into three treatments: (1) control, (2) infusing low SCFA, S1, (3) infusing high SCFA, S2. The experimental period lasted for 7 days.

Results

Gastric infusion of SCFA increased the concentrations of SCFA in serum and digesta, and enhanced the mRNA and protein abundances of SCFA receptors in pig intestine (P < 0.05). Moreover, gastric infusion of SCFA led to alteration of intestinal morphology, elevation of intestinal development-related gene abundances, and decrease of apoptotic cell percentage, as well as reduction of pro-apoptosis gene and protein abundances (P < 0.05). Besides, the jejunal SLC₇A₁ and ileal DMT1 mRNA abundances in the SCFA infusion groups were higher than those in the control group (P < 0.05). Additionally, gastric infusion of SCFA increased the mRNA abundances of Occludin and Claudin-1 in the duodenum and ileum, enhanced Lactobacillus spp counts in the ileal digesta, decreased the mRNA and protein abundances of IL-1β in the colon, and reduced Escherichia coli count in the ileal digesta (P < 0.05).

Conclusions

These data indicated that gastric infusion of SCFA, especially high SCFA concentration, may be beneficial to gut development of piglets via improving gut morphology, decreasing apoptotic cell percentage, and maintaining intestinal barrier function.

Electronic supplementary material

The online version of this article (10.1186/s12263-019-0626-x) contains supplementary material, which is available to authorized users.

Gut microbiota derived metabolites in cardiovascular health and disease

Trillions of microbes inhabit the human gut, not only providing nutrients and energy to the host from the ingested food, but also producing metabolic bioactive signaling molecules to maintain health and elicit disease, such as cardiovascular disease (CVD). CVD is the leading cause of mortality worldwide. In this review, we presented gut microbiota derived metabolites involved in cardiovascular health and disease, including trimethylamine-N-oxide (TMAO), uremic toxins, short chain fatty acids (SCFAs), phytoestrogens, anthocyanins, bile acids and lipopolysaccharide. These gut microbiota derived metabolites play critical roles in maintaining a healthy cardiovascular function, and if dysregulated, potentially causally linked to CVD. A better understanding of the function and dynamics of gut microbiota derived metabolites holds great promise toward mechanistic predicative CVD biomarker discoveries and precise interventions.

Biochemical Features of Beneficial Microbes: Foundations for Therapeutic Microbiology

Commensal and beneficial microbes secrete myriad products which target the mammalian host and other microbes. These secreted substances aid in bacterial niche development, and select compounds beneficially modulate the host and promote health. Microbes produce unique compounds which can serve as signaling factors to the host, such as biogenic amine neuromodulators, or quorum-sensing molecules to facilitate inter-bacterial communication. Bacterial metabolites can also participate in functional enhancement of host metabolic capabilities, immunoregulation, and improvement of intestinal barrier function. Secreted products such as lactic acid, hydrogen peroxide, bacteriocins, and bacteriocin-like substances can also target the microbiome. Microbes differ greatly in their metabolic potential and subsequent host effects. As a result, knowledge about microbial metabolites will facilitate selection of next-generation probiotics and therapeutic compounds derived from the mammalian microbiome. In this article we describe prominent examples of microbial metabolites and their effects on microbial communities and the mammalian host.

The interplay between host immune cells and gut microbiota in chronic inflammatory diseases

Many benefits provided by the gut microbiota to the host rely on its intricate interactions with host cells. Perturbations of the gut microbiota, termed gut dysbiosis, affect the interplay between the gut microbiota and host cells, resulting in dysregulation of inflammation that contributes to the pathogenesis of chronic inflammatory diseases, including inflammatory bowel disease, multiple sclerosis, allergic asthma and rheumatoid arthritis. In this review, we provide an overview of how gut bacteria modulates host metabolic and immune functions, summarize studies that examined the roles of gut dysbiosis in chronic inflammatory diseases, and finally discuss measures to correct gut dysbiosis as potential therapeutics for chronic inflammatory diseases.

Stimulation of intestinal growth with distal ileal infusion of short-chain fatty acid: a reevaluation in a pig model

18 barrows with average initial body weight of 30.72 (±1.48) kg fitted with a T-cannula in the terminal ileum were randomly allotted to 3 treatments to determine the underlying mechanisms of the regulation of SCFAs on intestinal development in a pig model.

The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism

Short-chain fatty acids (SCFAs), the end products of fermentation of dietary fibers by the anaerobic intestinal microbiota, have been shown to exert multiple beneficial effects on mammalian energy metabolism. The mechanisms underlying these effects are the subject of intensive research and encompass the complex interplay between diet, gut microbiota, and host energy metabolism. This review summarizes the role of SCFAs in host energy metabolism, starting from the production by the gut microbiota to the uptake by the host and ending with the effects on host metabolism. There are interesting leads on the underlying molecular mechanisms, but there are also many apparently contradictory results. A coherent understanding of the multilevel network in which SCFAs exert their effects is hampered by the lack of quantitative data on actual fluxes of SCFAs and metabolic processes regulated by SCFAs. In this review we address questions that, when answered, will bring us a great step forward in elucidating the role of SCFAs in mammalian energy metabolism.

Different feed withdrawal times before slaughter influence caecal fermentation and faecal Salmonella shedding in pigs

The effects of different pre-slaughter feed withdrawal times (FWT) on the gastrointestinal tract (GIT) weight and the gut environment of pigs and Salmonella shedding were investigated. Trial 1 evaluated the effects under experimental conditions (feed withdrawal for 18, 30 and 36 h) and trial 2 under commercial conditions (15 and 30 h). In trial 1, the GIT weight tended to decrease (P=0.07), the caecal pH increased (P<0.0001), short-chain fatty acids (SCFA) decreased (P<0.001) and percentage of branched-chain fatty acids (BCFA) increased as FWT increased. Similar results were observed in trial 2, but Enterobacteriaceae numbers and Salmonella positive pigs tended to increase whereas lactobacilli decreased (P<0.0005) as FWT increased. The increase in FWT involved changes in the gut microbial ecosystem that could be associated with the trend of increased caecal Enterobacteriaceae and Salmonella in faeces, and may represent a higher risk of carcass contamination in cases of laceration of viscera.

Risk factors for Salmonella enterica subsp. enterica shedding by market-age pigs in French farrow-to-finish herds

Fattening-pigs carriers of Salmonella enterica are believed to be a main source of carcass and pork contamination at the later steps of the meat process. We did a prospective study in 2000-2001 in 105 French farrow-to-finish pig farms. In each farm, a batch of contemporary fattening pigs housed in the same room was followed throughout the fattening period. Salmonella shedding was assessed on environmental samples of faecal material (taken by means of pairs of gauze socks) analysed by classical bacteriological methods. 36.2% of the batches studied had at least one contaminated environmental sample and therefore were classified as Salmonella-shedding batches. Logistic regression was used to assess the association between managerial and hygiene practices and health status and the shedding risk at the end of the finishing period. Emptying the pit below the slatted floor after the previous batch of sows was removed and frequent removal of sow dung during the lactation period were protective. Presence of residual Salmonella contamination of the floor and pen partitions in the fattening rooms before loading the growing pigs also was a risk factor. The risk for Salmonella shedding at the end of the fattening period was increased when dry feed (versus wet feed) was provided during the fattening period. Lastly, Lawsonia intracellularis seroconversion and PRRSV seropositivity during the fattening period also was a risk factor for Salmonella shedding.

Effect of fermented feed on shedding of Enterobacteriaceae by fattening pigs

Epidemiological studies showed that the use of fermented feed could significantly reduce Salmonella prevalence in pigs compared to the use of normal feed. Experimental challenge experiments with Salmonella have however never been conducted to reveal the efficacy of fermented feed in reducing Salmonella shedding and/or reducing the number of Salmonella-positive pigs. A longitudinal study was conducted to measure the effect of fermented feed, in particular of its components lactic acid and Lactobacillus plantarum, on gastrointestinal bacterial ecology (Salmonella, Enterobacteriaceae, lactobacilli, volatile fatty acids (VFAs), pH). Seeder pigs were used as a mode for Salmonella transmission within a pig herd. Bacteriological measurements were performed in faeces of the pigs. The results showed that fermented feed affected/reduced the Enterobacteriaceae population in faeces of the pigs. No differences were found in the number of positive pigs infected or in the number of shedding with Salmonella serovar Typhimurium fed fermented feed and between the normal feed group. S. serovar Goldcoast could not establish an infection in the seeder pigs in the fermented feed group as well as in the normal feed group. The pH of the faeces in the fermented feed groups was significantly higher than the pH of the faeces of the normal feed groups. The role of the undissociated form of the faecal VFAs on the significantly lower Enterobacteriaceae number in faeces of the pigs of the fermented feed groups could not be demonstrated because of the significant higher pH in the faeces of the pigs fed fermented feed.

Effect of fermented feed on the microbial population of the gastrointestinal tracts of pigs

An in vivo experiment was performed with pigs to study the inhibitory effect of fermented feed on the bacterial population of the gastrointestinal tract. Results demonstrated a significant positive correlation between pH and lactobacilli in the stomach contents of pigs in dry feed as well as in the stomach contents of pigs fed fermented feed. Furthermore, a significant positive correlation between the pH and the numbers of bacteria in the family Enterobacteriaceae in the contents of the stomach of pigs fed dry feed was found. In the stomach contents of pigs fed fermented feed, a significant negative correlation was found between the concentration of the undissociated form of lactic acid and the numbers of Enterobacteriaceae. The numbers of Enterobacteriaceae in the contents of the stomach, ileum, cecum, colon, and rectum of pigs fed fermented feed were significantly lower compared with the contents of the stomach, ileum, caecum, colon, and rectum of pigs fed dry feed. The numbers of total lactobacilli were significantly higher in the stomach contents of pigs fed fermented feed and in the ileum contents of one pig group fed fermented feed compared with the contents of pigs fed dry feed. However, the influence of lactobacilli on numbers of Enterobacteriaceae could not be demonstrated. It was concluded that fermented feed influences the bacterial ecology of the gastrointestinal tract and reduces the levels of Enterobacteriaceae in the different parts of the gastrointestinal tract.

Data-quality issues and alternative variable-screening methods in a questionnaire-based study on subclinical Salmonella enterica infection in Danish pig herds

Our aim was to determine risk factors for subclinical Salmonella enterica infection in Danish finishing-pig herds. In this paper, the evaluation, combining and initial reduction of variables is presented, along with assessment of the hypotheses in the preliminary statistical testing. The first group of herds was selected at random with no former knowledge of S. enterica infection. Both the herd prevalence and the within-herd prevalence among these herds turned out to be low; hence, some additional herds were selected from The Danish Salmonella Control program, based on their high seroprevalence. This resulted in a hybrid case-"control" design of the study and therefore, five different methods of categorising the data were used to ensure that variables were not wrongfully excluded as a result of using an improper design. Our questionnaire focused on management, infection-limiting precautions and feed and feeding procedures. To establish the prevalence of S. enterica infection within herds at the time of the visit, 50 blood samples from each herd were collected and serologically examined. The reliability of each variable from the questionnaire was assessed and it was decided which variables should be selected, disregarded, combined with other variables and/or recoded. In the simple statistical testing (2x2 tables, cut-off: P=0.25) herds were defined as subclinically S. enterica infected if the within-herd proportion of individual pigs with OD%>10 was more than 20%. The results included questionnaires from 96 randomly selected and 39 high-seroprevalence herds and 6814 blood samples. The initial 95 variables originally included in the questionnaires were reduced to 21 by critical check, combination, recoding and preliminary screening. We failed to demonstrate "herd size" as a risk factor for subclinical S. enterica infection in pig herds.