Swine Dysentery Research Articles

Colonic innate immune defenses and microbiota alterations in acute swine dysentery

Brachyspira hyodysenteriae, an etiologic agent of swine dysentery (SD), is known for causing colitis. Although some aspects of colonic defenses during infection have been described previously, a more comprehensive picture of the host and microbiota interaction in clinically affected animals is required. This study aimed to characterize multiple aspects of colonic innate defenses and microbiome factors in B. hyodysenteriae-infected pigs that accompany clinical presentation of hemorrhagic diarrhea. We examined colonic mucus barrier modifications, leukocyte infiltration, cathelicidin expression, as well as microbiome composition. We showed that B. hyodysenteriae infection caused microscopic hemorrhagic colitis with abundant neutrophil infiltration in the colonic lamina propria and lumen, with minor macrophage infiltration. Mucus hypersecretion with abundant sialylated mucus in the colon, as well as mucosal colonization by [Acetivibrio] ethanolgignens, Lachnospiraceae, and Campylobacter were pathognomonic of B. hyodysenteriae infection. These findings demonstrate that B. hyodysenteriae produces clinical disease through multiple effects on host defenses, involving alterations of mucosal innate immunity and microbiota. Given that B. hyodysenteriae is increasingly resistant to antimicrobials, this understanding of SD pathogenesis may lead to future development of non-antibiotic and anti-inflammatory alternative therapeutics.

Experimental natural transmission (seeder pig) models for reproduction of swine dysentery.

Swine dysentery is causally associated with Brachyspira hampsonii and B. hyodysenteriae infection. Given the importance of transmission models in understanding re-emergent diseases and developing control strategies such as vaccines, the objective of this experiment was to evaluate two experimental natural transmission (seeder pig) models in grower pigs, each with 24 animals. Seeder pigs were intragastrically inoculated using broth cultures of either B. hampsonii strain 30446 (genomovar II) or B. hyodysenteriae strain G44. In trial 1, three seeder pigs were placed into two pens containing nine susceptible contact pigs creating a 1:3 seeder:contact ratio. This was sufficient to achieve natural B. hampsonii infection of 13/18 (72%) contact pigs, however, the incidence of mucoid or mucohemorrhagic diarrhea (MMHD) in contact pigs differed significantly between pens (4/9 versus 9/9; P = 0.03). In trial 2, eight seeder pigs inoculated intragastrically with B. hampsonii did not develop MMHD but when re-inoculated with B. hyodysenteriae 14 days later, all developed mucohemorrhagic diarrhea within 13 days of re-inoculation. Two seeder pigs were placed into each of 4 contact pens each containing 4 pigs. This 1:2 seeder:contact ratio resulted in natural infection of 14/16 (87%) contact pigs with incubation period ranging from 9–15 days. There were no significant differences among pens in incubation period, duration, clinical period or severity of diarrhea. These trials demonstrated that a 1:2 seeder:contact ratio with groups of six grower pigs per pen sustained natural transmission of B. hyodysenteriae G44 with greater consistency in the incidence of MMHD among pens compared to a B. hampsonii 30446 transmission model using 1:3 seeder:contact ratio in pens of 12. Understanding why B. hampsonii intragastric inoculation failed in one experiment warrants additional research.

In Vitro Screening of Non-Antibiotic Components to Mitigate Intestinal Lesions Caused by Brachyspira hyodysenteriae, Lawsonia intracellularis and Salmonella enterica Serovar Typhimurium.

Simple SummaryThe prevention, treatment, and control of swine dysentery, ileitis, and porcine salmonellosis diseases, respectively, caused by infection with Brachyspira hyodysenteriae, Lawsonia intracellularis, and Salmonella enterica serovar Typhimurium, still relies on the use of antimicrobials. The goal of this study was to evaluate the effectiveness of four commercially available non-antimicrobial compounds in preventing lesions caused by these bacteria using an in vitro intestinal culture model. The findings suggest that the non-antimicrobial compounds studied may have beneficial effects for the host based on the explant model data shown. These findings represent a step towards finding alternatives to antimicrobials usage and control of swine diseases in pork production.Swine dysentery, ileitis, and porcine salmonellosis are production-limiting diseases of global importance for swine production. They are caused by infection with Brachyspira hyodysenteriae, Lawsonia intracellularis, and Salmonella enterica serovar Typhimurium, respectively. Currently, the prevention, treatment, and control of these diseases still relies on antimicrobials. The goal of this study was to evaluate the effectiveness of four commercially available non-antimicrobial compounds in preventing lesions caused by the bacteria cited above using an in vitro intestinal culture model. A total of five pigs per pathogen were used and multiple compounds were evaluated. For compound F (a fungal fermented rye), S (a blend of short and medium chain fatty acids), and P (a synergistic blend of short and medium chain fatty acids, including coated butyrates), a total of four explants/pig for each treatment were used, while for compound D (an extract of carob and thyme) only 12 explants/pig for each treatment were used. Explants were exposed to a combination of pathogen only (n = 4/compound/pig), compound only (n = 4/compound/pig), or pathogen and compound (n = 4/compound/pig) and sampled at two time-points. Histopathology and gene expression levels were evaluated to investigate the treatment effect on explants. Short and medium-chain fatty acids, and an extract of carob and thyme, was found to mitigate lesions due to B. hyodysenteriae exposure. A fungal fermented prebiotic increased healthy epithelial coverage when explants were exposed to L. intracellularis or S. Typhimurium. These findings represent a step towards finding alternatives to antimicrobials usage and control of swine dysentery, ileitis, and salmonellosis in pork production.

Experimental Infection of Pigs with a ST 245 Brachyspira hyodysenteriae Isolated from an Asymptomatic Pig in a Herd with No History of Swine Dysentery

Swine dysentery (SD) is characterized by a severe mucohemorrhagic colitis caused by infection with Brachyspira species. In infected herds the disease causes considerable financial loss due to mortality, slow growth rates, poor feed conversion, and costs of treatment. B. hyodysenteriae is the most common etiological agent of SD and infection is usually associated with disease. However, isolated reports have described low pathogenic strains of B. hyodysenteriae. The aim of this study was to describe an experimental infection trial using a subclinical B. hyodysenteriae isolated from an animal without clinical signs and from a disease-free herd, to evaluate the pathogenicity and clinical pathological characteristics compared to a highly clinical isolate. Forty-eight 5-week-old pigs were divided into three groups: control, clinical and the subclinical isolates. The first detection/isolation of B. hyodysenteriae in samples of the animals challenged with a known clinical B. hyodysenteriae strain (clinical group) occurred 5th day post inoculation. Considering the whole period of the study, 11/16 animals from this group were qPCR positive in fecal samples, and diarrhea was observed in 10/16 pigs. In the subclinical isolate group, one animal had diarrhea. There were SD large intestine lesions in 3 animals at necropsy and positive B. hyodysenteriae isolation in 7/15 samples of the subclinical group. In the control group, no diarrhea, gross/microscopic lesions, or qPCR positivity were observed. Clinical signs, bacterial isolation, macroscopic and histologic lesions were significantly difference among groups, demonstrating low pathogenicity of the subclinical isolate in susceptible pigs.

Carriage of Brachyspira hyodysenteriae on common insect vectors

The interactions of likely insect and murine vectors of the causative agent of swine dysentery, Brachyspira hyodysenteriae, were investigated. Insects were collected and analysed from 3 pig farms positive for B hyodysenteriae. Within these farms, several Musca domestica and Orphyra adult fly, Blatta sp. cockroach digestive tracts and hover fly (Eristalis sp) pupal form contents were positive in a standard PCR assay for B hyodysenteriae, whereas all other insect samples on these and case control farms were negative. In challenge exposure studies, B hyodysenteriae DNA was detected in the digestive tract of cockroaches and M domestica flies from day 1 post-inoculation with cultured B hyodysenteriae, for up to 5 days or 10 days respectively, while control non-inoculated insects remained negative. Isolates consistent with B hyodysenteriae were only cultured from frass samples of these inoculated cockroach and flies on days 1–3 post-inoculation. Isolates consistent with B hyodysenteriae were detected by analysis of agar plates exposed to live B hyodysenteriae-inoculated adult flies wandering and feeding on these plates for 20 min per day. In generational challenge inoculation studies, B hyodysenteriae was detected in the adult emergent flies, and internal components of fly pupae on days 1–7 of the pupation period, after being inoculated with B hyodysenteriae as larvae. Five-week-old conventional mice (C3H) that consumed 2 meals of B hyodysenteriae-infected flies remained negative for B hyodysenteriae throughout the next 10 days. The results indicated that pathogenic Brachyspira sp have a limited ability to internally colonise likely insect vectors and do not readily transmit infection to mice. However, the insect vectors analysed were demonstrably capable of mechanical carriage and likely on-farm involvement in consequence.

Factors driving pig owners’ motivation and satisfaction to perform eradications from Swine dysentery

Brachyspira hyodysenteriae is one of the agents of swine dysentery (SD) and its eradication is an effective, but costly control measure. Being a voluntary measure, knowledge about drivers of motivation and satisfaction regarding the eradication of SD would help to convince farmers to eradicate. We aimed to describe eradications performed in Switzerland and to analyse factors influencing the pig owners’ perception (motivation and satisfaction) of SD eradications to provide a basis to formulate recommendations and guidelines. Pig farmers (n = 68) having conducted an SD eradication and being interested in the study were interviewed using a standardised digital questionnaire. We assessed their motivation as moderately or highly motivated. Based on the farmers’ evaluation of nine aspects of the eradication, satisfaction was considered to be moderate (<7/9 aspects positively evaluated) or high (≥7/9). Farms with fattening pigs and farms with breeding stock were analysed separately in subsets. First, multivariable factor analysis for mixed data (FAMD) were performed to describe the main patterns of variation. Then, risk factors for motivation and satisfaction were quantified by means of logistic regression models. Mainly total depopulations (73.5%) had been performed. Of the 36 farmers with breeding pigs, 24 were highly motivated, and 20 highly satisfied. Of the 61 farmers with fattening pigs, 45 were highly motivated and 42 highly satisfied. The FAMD revealed that the two main components explained only 17.0% and 11.0% (breeding stock) and 13.0% and 11.0% (fattening pigs) of the total variation, respectively. For farmers with breeding stock no significant factors for motivation were detected, but they were more satisfied (OR 25.0) when they had a batch farrowing of 3 weeks. Farmers with fattening pigs were more likely to be more motivated when providing access to outdoor areas (OR 3.3) and when it was their own initiative (OR 5.5). Farmers were more likely to be satisfied when they had only fattening pigs (OR 5.7), when the eradication was their own initiative (OR 5.5) and when they did not disinfect the barns during the eradication (OR 15.6). Farmers deciding themselves to eradicate are presumably more likely convinced of the benefits of the eradication. Satisfaction associated with a 3-weeks batch farrowing might be related to an easier to organise eradication and no disinfection to reduced labour and costs. In summary, the majority of the farmers were satisfied with the eradication. Education could promote self-motivation of farmers, and subsidies might support the implementation of SD eradications.

Influence of infection with Brachyspira hyodysenteriae on clinical expression, growth performance, and digestibility in growing pigs fed diets varying in type and level of fiber.

Research on the effects of different fiber types and levels on infection with Brachyspira hyodysenteriae on growth performance and nutrients digestibility in pigs is scarce. The objective of the current study was to investigate the effects of infection with B. hyodysenteriae when feeding diets varying in soluble and insoluble dietary fiber (DF) on the expression of swine dysentery, growth performance, and digestibility of organic matter (OM) nutrients. A total of 96 growing pigs (26.9 ± 2.5 kg) were used for the experiment and divided into six blocks. The growing pigs were fed one of four diets for 12 wk: low fiber (LF), high fiber (HF), high soluble fiber (HS), and high insoluble fiber (HI). After 2 wk, half of the pigs were inoculated with B. hyodysenteriae. Half of the pigs in each group were euthanized at week 6 for the measurement of the apparent digestibility at the ileum, cecum, colon, and total tract. The remaining pigs were maintained to observe and analyze the clinical expression of fecal score and excretion of B. hyodysenteriae, growth performance, and total tract digestibility up to 12 wk. In the current study, the experimental diets did not influence the expression of infection in the pigs. The body weight and average daily gain (ADG) were in line with the results of clinical expression from week 4 to 6. However, the ADG of the infected pigs started to recover from week 6 (P < 0.05) and then recovered from week 8 to 12 (P < 0.05). The infection with B. hyodysenteriae did not impair apparent ileal digestibility (AID; P > 0.05), whereas the apparent digestibility of OM, total non-starch polysaccharide, non-cellulosic polysaccharide, and cellulose in the cecum of the infected pigs was higher than non-infected pigs (P < 0.05). The apparent colonic digestibility of ash and nitrogen was higher in non-infected pigs than in infected pigs (P < 0.05). The pigs fed the LF diet had a higher digestibility in all segments of the intestinal tract, whereas the HS diet had the lowest AID but higher or similar to the LF diet in the cecum, colon, and the total tract (P < 0.05). The pigs fed the HF and HI diets, with a high proportion of insoluble fiber, had a lower digestibility in the hindgut than the other two diets (P < 0.05). In conclusion, the infection with B. hyodysenteriae negatively influenced clinical signs of swine dysentery and growth performance but did not impair AID, and neither soluble nor insoluble DF influenced the expression of the infection.

Whole-genome analyses reveal a novel prophage and cgSNPs-derived sublineages of Brachyspira hyodysenteriae ST196

BackgroundBrachyspira (B.) hyodysenteriae is a fastidious anaerobe spirochete that can cause swine dysentery, a severe mucohaemorragic colitis that affects pig production and animal welfare worldwide. In Switzerland, the population of B. hyodysenteriae is characterized by the predominance of macrolide-lincosamide-resistant B. hyodysenteriae isolates of sequence type (ST) ST196, prompting us to obtain deeper insights into the genomic structure and variability of ST196 using pangenome and whole genome variant analyses.ResultsThe draft genome of 14 B. hyodysenteriae isolates of ST196, sampled during a 7-year period from geographically distant pig herds, was obtained by whole-genome sequencing (WGS) and compared to the complete genome of the B. hyodysenteriae isolate Bh743-7 of ST196 used as reference. Variability results revealed the existence of 30 to 52 single nucleotide polymorphisms (SNPs), resulting in eight sublineages of ST196. The pangenome analysis led to the identification of a novel prophage, pphBhCH20, of the Siphoviridae family in a single isolate of ST196, which suggests that horizontal gene transfer events may drive changes in genomic structure.ConclusionsThis study contributes to the catalogue of publicly available genomes and provides relevant bioinformatic tools and information for further comparative genomic analyses for B. hyodysenteriae. It reveals that Swiss B. hyodysenteriae isolates of the same ST may have evolved independently over time by point mutations and acquisition of larger genetic elements. In line with this, the third type of mobile genetic element described so far in B. hyodysenteriae, the novel prophage pphBhCH20, has been identified in a single isolate of B. hyodysenteriae of ST196.

Diversity and potential genetic relationships amongst Brazilian Brachyspira hyodysenteriae isolates from cases of swine dysentery

The aim of this study was to evaluate genetic diversity, distribution, evolution and population structure of Brazilian Brachyspira hyodysenteriae strains isolated from swine. Multilocus Sequence Typing (MLST) analysis using seven housekeeping genes was applied to 46 isolates obtained from outbreaks of swine dysentery that occurred between 2011 and 2015 in the states of Minas Gerais, São Paulo, Mato Grosso, Rio Grande do Sul and Santa Catarina. Historical isolates from Rio Grande do Sul obtained in 1998 were also included in the study. An independent international profile of the global sequences deposited in the B. hyodysenteriae database was used for comparisons with the Brazilian strains. All isolates from 2011 to 2015 were classified into nine sequence type (STs) and divided into four clonal complexes. These findings indicated genetic relationships among the B. hyodysenteriae from different Brazilian states, among historical strains isolated in 1998 and from recent outbreaks, and relatedness with global isolates. Seven STs were unique and, to date, only reported in Brazil.

Detection of Swine Dysentery (SD) caused by Brachyspira hyodysenteriae via PCR in Northern Vietnam

This study aimed to diagnose swine dysentery (SD) caused by Brachyspira hyodysenteriae in pigs by the PCR method in Vietnam. Of the 250 samples, 29 isolates of B. hyodysenteriae (11.60%) were identified by PCR in seven provinces of Northern Vietnam, and the infection rate differed from region to region. From the positive cases of B. hyodysenteriae, we analyzed B. hyodysenteriae infected cases according to the ages of the pigs, farm sizes, and veterinary hygiene practices to get more information about the disease in Vietnam. The results showed that the positive B. hyodysenteriae samples were commonly seen in post-weaning pigs (32.14%) in households (20.73%) with poor hygiene (24.69%). Clinical signs of SD included high fever (100%); anorexia (100%); watery, bloody diarrhea, usually gray to brown in color (100%); and weight loss (86.42%). Gross lesions of SD were limited to the large intestine were described as having a fibrinous, blood-flecked membrane covering the mucosa (93.75%), swollen with hemorrhaged colon and cecum (75.00%), and mesenteric lymph nodes (81.25%).

Balantidium Coli in Pig Farms Suspected of Porcine Circovirus Type 2 (PCV2) Associated Enteritis.

IntroductionDiarrhoea in growing-finishing pigs is a common problem of commercial pig farms. Among many causative factors, porcine circovirus type 2 (PCV2) is one considered an important pathogen in modern pig production. The aim of the study was to verify if PCV2 was responsible for antibiotic non-responsive diarrhoea and wasting in pigs.Material and MethodsA total of 13 dead pigs aged between 12 and 15 weeks from three Polish farms with persistent herd symptoms suggestive of PCV2 infection were provided for evaluation. Sections of lymph nodes and intestines were analysed by in situ hybridization (ISH) for PCV2 and histopathological examination. Faeces and intestinal scrapings were tested for Lawsonia intracellularis and Brachyspira hyodysenteriae by real-time PCR and for parasitic infection by flotation and decantation.ResultsISH and histopathological examination showed that all pigs were PCV2 systemic disease negative. Swine dysentery was confirmed by real-time PCR on two farms, and proliferative enteropathy on one farm. In histological examinations, erosions of the caecal and colonic mucosa were found, together with cysts and trophozoites of Balantidium coli. The protozoa were present in the intestinal lumen and mucosa. B. coli cysts were identified in faeces from all examined pigs.ConclusionThese results suggest that monitoring of B. coli infections should be an additional measure of control and prevention of gastrointestinal tract disorders in modern swine husbandry.

Complete Circular Genome Sequences of Brachyspira hyodysenteriae Isolates of the Four Different Sequence Types Causing Swine Dysentery in Switzerland

ABSTRACTThe complete genomes of four Brachyspira hyodysenteriae isolates of the four different sequence types (STs) (ST6, ST66, ST196, and ST197) causing swine dysentery in Switzerland were generated by whole-genome sequencing and de novo hybrid assembly of reads obtained from second (Illumina) and third (Oxford Nanopore Technologies and Pacific Biosciences) generation high-throughput sequencing.

Brachyspira Species Avidity to Colonic Mucins from Pigs with and without Brachyspira hyodysenteriae Infection Is Species Specific and Varies between Strains.

Brachyspira hyodysenteriae is commonly associated with swine dysentery (SD), a disease that has an economic impact on the swine industry. B. hyodysenteriae infection results in changes to the colonic mucus niche with massive mucus induction, which substantially increases the number of B. hyodysenteriae binding sites in the mucus. We previously determined that a B. hyodysenteriae strain binds to colon mucins in a manner that differs between pigs and mucin types. Here, we investigated if adhesion to mucins is a trait observed across a broad set of B. hyodysenteriae strains and isolates and furthermore at a genus level (B. innocens, B. pilosicoli, B. murdochii, B. hampsonii, and B. intermedia strains). Our results show that binding to mucins appears to be specific to B. hyodysenteriae, and within this species, the binding ability to mucins varies between strains/isolates, increases for mucins from pigs with SD, and is associated with sialic acid epitopes on mucins. Infection with B. hyodysenteriae strain 8dII results in mucin glycosylation changes in the colon, including a shift in sialic acid-containing structures. Thus, we demonstrate through hierarchical cluster analysis and orthogonal projections to latent structures discriminant analysis (OPLS-DA) models of the relative abundances of sialic acid-containing glycans that sialic acid-containing structures in the mucin O-glycome are good predictors of B. hyodysenteriae strain 8dII infection in pigs. The results emphasize the role of sialic acids in governing B. hyodysenteriae interactions with its host, which may open perspectives for therapeutic strategies.

Whole-Genome Sequencing of Brachyspira hyodysenteriae Isolates From England and Wales Reveals Similarities to European Isolates and Mutations Associated With Reduced Sensitivity to Antimicrobials.

Brachyspira hyodysenteriae is the principal cause of swine dysentery, a disease that threatens economic productivity of pigs in many countries as it can spread readily within and between farms, and only a small number of antimicrobials are authorized for treatment of pigs. In this study, we performed whole-genome sequencing (WGS) of 81 B. hyodysenteriae archived at the Animal and Plant Health Agency (APHA) from diagnostic submissions and herd monitoring in England and Wales between 2004 and 2015. The resulting genome sequences were analyzed alongside 34 genomes we previously published. Multi-locus sequence typing (MLST) showed a diverse population with 32 sequence types (STs) among the 115 APHA isolates, 25 of them identified only in England; while also confirming that the dominant European clonal complexes, CC8 and CC52, were common in the United Kingdom. A core-genome SNP tree typically clustered the isolates by ST, with isolates from some STs detected only within a specific region in England, although others were more widespread, suggesting transmission between different regions. Also, some STs were more conserved in their core genome than others, despite these isolates being from different holdings, regions and years. Minimum inhibitory concentrations to commonly used antimicrobials (Tiamulin, Valnemulin, Doxycycline, Lincomycin, Tylosin, Tylvalosin) were determined for 82 of the genome-sequenced isolates; genomic analysis revealed mutations generally correlated well with the corresponding resistance phenotype. There was a major swine dysentery intervention program in 2009–2010, and antimicrobial survival curves showed a significant reduction in sensitivity to tiamulin and valnemulin in isolates collected in and after 2010, compared to earlier isolates. This correlated with a significant increase in post-2009 isolates harboring the pleuromutilin resistance gene tva(A), which if present, may facilitate higher levels of resistance. The reduction in susceptibility of Brachyspira from diagnostic submissions to pleuromutilins, emphasizes the need for prudent treatment, control and eradication strategies.

Alteration of Colonic Mucin Composition and Cytokine Expression in Acute Swine Dysentery.

Swine dysentery (SD) is an enteric disease associated with strongly β-hemolytic Brachyspira spp. that cause mucohemorrhagic diarrhea primarily in grower-finisher pigs. We characterized alteration of colonic mucin composition and local cytokine expression in the colon of pigs with acute SD after B. hyodysenteriae (Bhyo) infection and fed either a diet containing 30% distillers dried grains with solubles (DDGS) or a control diet. Colonic tissue samples from 9 noninoculated pigs (Control, N = 4; DDGS, N = 5) and 10 inoculated pigs experiencing acute SD (Bhyo, N = 4; Bhyo-DDGS, N = 6) were evaluated. At the apex of the spiral colon, histochemical staining with high-iron diamine-Alcian blue revealed increased sialomucin (P = .008) and decreased sulfomucin (P = .027) in Bhyo pigs relative to controls, with a dietary effect for sulfomucin. Noninoculated pigs fed DDGS had greater expression of sulfomucin (P = .002) compared to pigs fed the control diet. Immunohistochemically, there was de novo expression of mucin 5AC (MUC5AC) in the Bhyo group while mucin 2 (MUC2) expression was not significantly different between groups. RNA in situ hybridization to detect the pro-inflammatory cytokine IL-1β often showed increased expression in the Bhyo group although without statistical significance, and this was not correlated with MUC5AC or MUC2 expression, suggesting IL-1β is not a major regulator of their secretion in acute SD. Expression of the anti-inflammatory cytokine TGF-β1 was significantly suppressed in the Bhyo group compared to controls (P = .005). This study reveals mucin and cytokine alterations in the colon of pigs with experimentally induced SD and related dietary effects of DDGS.

Highly Fermentable Fiber Alters Fecal Microbiota and Mitigates Swine Dysentery Induced by Brachyspira hyodysenteriae.

Brachyspira hyodysenteriae is an etiological agent of swine dysentery (SD). Diet fermentability plays a role in development of SD, but the mechanism(s) of action are largely unknown. Thus, this study aimed to determine whether replacing lowly fermentable fiber with highly fermentable fiber would mitigate a 42 d B. hyodysenteriae challenge. Thirty-nine barrows were allocated to dietary treatment groups: (1) 20% corn distillers dried grain with solubles (DDGS), 0% beet pulp (BP) or resistant starch (RS; lowly fermentable fiber (LFF)); (2) 10% DDGS, 5% BP, 5% RS (medium fermentable fiber (MFF)); and (3) 0% DDGS, 10% BP, 10% RS (highly fermentable fiber (HFF)). On day post inoculation 0, pigs were inoculated with B. hyodysenteriae. Overall, 85% LFF pigs developed clinical SD, 46% of MFF pigs developed SD, and 15% of HFF pigs developed SD (p < 0.05). Overall average daily gain (ADG) differed among all treatments (p < 0.001), with LFF pigs having the lowest ADG. For HFF pigs, ADG was 37% greater than LFF pigs (p < 0.001) and 19% greater than MFF pigs (p = 0.037). The LFF diet had greater relative abundance of Shuttleworthia and Ruminococcus torques. Further, microbiota of pigs that developed SD had enriched Prevotellaceae. Collectively, replacing DDGS with highly fermentable fiber reduced clinical SD, improved performance, and modulated fecal microbiota during B. hyodysenteriae challenge.

Brachyspira hyodysenteriae Infection Reduces Digestive Function but Not Intestinal Integrity in Growing Pigs While Disease Onset Can Be Mitigated by Reducing Insoluble Fiber.

Swine dysentery (SD) induced by Brachyspira hyodysenteriae manifests as mucohemorrhagic diarrhea in pigs, but little is known about the changes that occur to the gastrointestinal tract during this disease. It is thought that dietary fibers alter disease pathogenesis, although the mechanisms of action are unclear. Thus, the objectives of this study were to characterize intestinal integrity, metabolism, and function in pigs during SD and determine if replacing insoluble fiber with fermentable fibers mitigates disease. Thirty-six B. hyodysenteriae-negative gilts [24.3 ± 3.6 kg body weight (BW)] were assigned to one of three treatment groups: (1) B. hyodysenteriae negative, control diet (NC); (2) B. hyodysenteriae challenged, control diet (PC); and (3) B. hyodysenteriae challenged, highly fermentable fiber diet (RS). The NC and PC pigs were fed the same control diet, containing 20% corn distillers dried grains with solubles (DDGS). The RS pigs were fed a diet formulated with 5% sugar beet pulp and 5% resistant potato starch. On days post inoculation (dpi) 0 and 1, pigs were inoculated with B. hyodysenteriae or sham. Pigs were euthanized for sample collection after onset of SD. The challenge had high morbidity, with 100% of PC and 75% of RS pigs developing clinical SD. The timing of onset of clinical SD differed due to treatment, with RS pigs having a delayed onset (dpi 9) of clinical SD compared with dpi 7 for PC pigs. Colon transepithelial resistance was increased and macromolecule permeability was reduced in PC pigs compared with NC pigs (P < 0.01). Minimal changes in ileal permeability, mitochondrial function, or volatile fatty acids (VFAs) were observed. Total VFA concentrations were lower in the colon and cecum in both PC and RS pigs compared to NC pigs (both P < 0.05), but iso-acids were higher (both P < 0.05). Total tract digestibility of dry matter (DM), organic matter (OM), nitrogen (N), and gross energy (GE) was lower in PC pigs compared with both NC and RS pigs (both P < 0.001). These data indicate that SD reduces digestive function but does not reduce ex vivo intestinal integrity. Further, replacement of insoluble fiber with highly fermentable fibers mitigated and delayed the onset of SD.

Swine dysentery disease mechanism: Brachyspira hampsonii impairs the colonic immune and epithelial repair responses to induce lesions

Swine dysentery (SD) is a global, production-limiting disease of pigs in commercial farms. It is associated with infection by Brachyspira hyodysenteriae and B. hampsonii, and characterized by mucohaemorrhagic diarrhea and colitis, SD prevention, treatment or control relies heavily on antimicrobials as no commercial vaccines are available. This is linked to our poor understanding of the disease pathogenesis. Our goal was to characterize the host-pathogen interactions during the early stage of infection. We employed dual RNA-seq to profile mRNA and miRNA following 1-h incubation of colonic explants with a pathogenic or a non-pathogenic B. hampsonii strain. Our results suggest that the pathogenic strain more efficiently interfered with the host's ability to activate and build a humoral response (through IL-4/CCR6/KLHL6 interactions), epithelial wound repair mechanisms (associated with LSECtin impairment of macrophages), induced mitochondrial dysfunction (linked to MDR1), and loss of microbiome homeostasis. The pathogenic strain also up-regulated the expression of stress-associated genes, when compared to the non-pathogenic strain. These results shed a light on the pathophysiological mechanisms that lead to SD and will contribute to the development of novel disease control tools.

Differential expression of hemolysin genes in weakly and strongly hemolytic Brachyspira hyodysenteriae strains

BackgroundSwine dysentery (SD) is a diarrheal disease in fattening pigs that is caused by the strongly hemolytic species Brachyspira (B.) hyodysenteriae, B. hampsonii and B. suanatina. As weakly hemolytic Brachyspira spp. are considered less virulent or even non-pathogenic, the hemolysin is regarded as an important factor in the pathogenesis of SD. Four hemolysin genes (tlyA, tlyB, tlyC, and hlyA) and four putative hemolysin genes (hemolysin, hemolysin activation protein, hemolysin III, and hemolysin channel protein) have been reported, but their role in strong hemolysis is not entirely clear. Our study aimed to assess the transcriptional activity of eight (putative) hemolysin genes in a strongly hemolytic (B204) and a weakly hemolytic (G423) B. hyodysenteriae strain during non-hemolytic and hemolytic growth stages.ResultsStrongly and weakly hemolytic B. hyodysenteriae strains caused hemolysis on blood agar at different growth stages, namely during log phase (B204) and stationary/death phase (G423). During the lag, early log, late log (stationary phase in G423) and death phase (time points 1–4) strains differed in their hemolysin gene transcription patterns. At time point 1, transcription of the putative hemolysin gene was higher in B204 than in G423. At time point 2, tlyA and tlyC were upregulated in B204 during hemolysis. TlyB and hlyA were upregulated in both strains at all time points, but higher transcription rates were observed in the weakly hemolytic strain G423. The transcription activity of the hemolysin channel protein gene was quite similar in both strains, whereas the hemolysin activation protein gene was upregulated in the non-hemolytic stage of B204 at time point 4. Sequence analysis revealed deletions, insertions and single nucleotide polymorphisms in the G423 hlyA promoter, although without altering the transcription activity of this gene.ConclusionOur data indicate a combined activity of TlyA and TlyC as the most probable underlying mechanism of strong hemolysis in B. hyodysenteriae. Further studies should verify if the expression of tlyA is upregulated by the putative hemolysin gene. Depending on their immunogenic potential TlyA and TlyC may serve as possible vaccine candidates, especially since vaccines for an effective control of swine dysentery are currently not available.

Spirochete Flagella and Motility.

Spirochetes can be distinguished from other flagellated bacteria by their long, thin, spiral (or wavy) cell bodies and endoflagella that reside within the periplasmic space, designated as periplasmic flagella (PFs). Some members of the spirochetes are pathogenic, including the causative agents of syphilis, Lyme disease, swine dysentery, and leptospirosis. Furthermore, their unique morphologies have attracted attention of structural biologists; however, the underlying physics of viscoelasticity-dependent spirochetal motility is a longstanding mystery. Elucidating the molecular basis of spirochetal invasion and interaction with hosts, resulting in the appearance of symptoms or the generation of asymptomatic reservoirs, will lead to a deeper understanding of host–pathogen relationships and the development of antimicrobials. Moreover, the mechanism of propulsion in fluids or on surfaces by the rotation of PFs within the narrow periplasmic space could be a designing base for an autonomously driving micro-robot with high efficiency. This review describes diverse morphology and motility observed among the spirochetes and further summarizes the current knowledge on their mechanisms and relations to pathogenicity, mainly from the standpoint of experimental biophysics.