New insights into swine dysentery: faecal shedding, macro and microscopic lesions and biomarkers in early and acute stages of Brachyspira hyodysenteriae infection.

BACKGROUND: Swine dysentery (SD) is a severe mucohaemorrhagic colitis in pigs caused classically by Brachyspira hyodysenteriae. Although several aspects of B. hyodysenteriae infection dynamic are already described, further research in the early stage of this infection is required. In this study, 7-week-old pigs were orally challenged with B. hyodysenteriae to obtain information about faecal shedding, macro and microscopic intestinal lesions and serum acute phase proteins in pigs at the onset of B. hyodysenteriae shedding (early infection group, n = 8), in pigs with mucohaemorrhagic diarrhoea (acute infection group, n = 8) and in non-infected controls (n = 16). RESULTS: First B. hyodysenteriae detection by q-PCR and first loose stools with blood and mucus occurred both at 8 days post-inoculation. The lapse between a positive q-PCR and observation of mucohaemorrhagic diarrhoea ranged from 0 to 3 days, except in a single pig in which this period lasted 5 days. Macroscopic lesions were observed in the large intestine from both infected groups although more frequent and severe in acute infection group. Microscopic observation of the apex mucosa revealed that in early infection only higher ulceration values were observed compared to healthy controls. In contrast, the acute infection group exhibited higher ulceration, neutrophils infiltration and increased mucosal thickness compared to the other two groups. Among the serum biomarkers tested, only haptoglobin, C-reactive protein, and creatine kinase showed a significant increase in pigs in the acute infection period compared to controls, whereas haptoglobin was the only factor with a significant increase at the early infection compared to non-infected animals. CONCLUSIONS: This study provides new insights about SD and remarks the complex and limited options to perform an early detection of infected animals beyond PCR diagnosis.

First molecular detection of Brachyspira hampsonii on pig farms in Poland.

Nowadays, the three strongly beta-haemolytic spirochaetes, Brachyspira hyodysenteriae, Brachyspira suanatina and Brachyspira hampsonii are thought to be causative agents of swine dysentery, an economically devastating disease of grow-finish pigs characterised by severe mucohaemorrhagic diarrhoea. B. hyodysenteriae has been reported in most leading swine-producing regions. B. suanatina and B. hampsonii have been successfully recovered from faecal samples collected in a few countries only. The present study was performed in March 2023 on faecal samples originating from nine Polish finisher farms with 6,000 to 18,000 animals in a location. Samples were obtained from 40 diarrhoeic finishers. Nucleic acid extracted from the samples was analysed using multiplex PCR for Brachyspira spp. From a total of nine sample populations examined in our study, the genetic material of B. hampsonii was identified in two. To the best of our knowledge, this is the first report on molecular detection of B. hampsonii on pig farms outside North America, Belgium and Germany. Our research highlights the need for increased focus directed on laboratory testing strategies, the lack of which may perplex swine practitioners and severely hinder a definite diagnosis.

T-independent B-cell effect of agents associated with swine grower-finisher diarrhea.

Swine dysentery, spirochetal colitis, and salmonellosis are production-limiting enteric diseases of global importance to the swine industry. Despite decades of efforts, mitigation of these diseases still relies on antibiotic therapy. A common knowledge gap among the 3 agents is the early B-cell response to infection in pigs. Thus, this study aimed to characterize the porcine B-cell response to Brachyspira hyodysenteriae, Brachyspira hampsonii (virulent and avirulent strains), Brachyspira pilosicoli, and Salmonella Typhimurium, the agents of the syndromes mentioned above. Immortalized porcine B-cell line derived from a crossbred pig with lymphoma were co-incubated for 8 h with each pathogen, as well as E. coli lipopolysaccharide (LPS) and a sham-inoculum (n = 3/treatment). B-cell viability following treatments was evaluated using trypan blue, and the expression levels of B-cell activation-related genes was profiled using reverse transcription quantitative PCR. Only S. Typhimurium and LPS led to increased B-cell mortality. B. pilosicoli downregulated B-lymphocyte antigen (CD19), spleen associated tyrosine Kinase (syk), tyrosine-protein kinase (lyn), and Tumour Necrosis Factor alpha (TNF-α), and elicited no change in immunoglobulin-associated beta (CD79b) and swine leukocyte antigen class II (SLA-DRA) expression levels, when compared to the sham-inoculated group. In contrast, all other treatments significantly upregulated CD79b and stimulated responses in other B-cell downstream genes. These findings suggest that B. pilosicoli does not elicit an immediate T-independent B-cell response, nor does it trigger antigen-presenting mechanisms. All other agents activated at least one trigger within the T-independent pathways, as well as peptide antigen presenting mechanisms. Future research is warranted to verify these findings in vivo.

Antimicrobial susceptibility of U.S. porcine Brachyspira isolates and genetic diversity of B. hyodysenteriae by multilocus sequence typing.

Swine dysentery, caused by Brachyspira hyodysenteriae and the newly recognized Brachyspira hampsonii in grower-finisher pigs, is a substantial economic burden in many swine-rearing countries. Antimicrobial therapy is the only commercially available measure to control and prevent Brachyspira-related colitis. However, data on antimicrobial susceptibility trends and genetic diversity of Brachyspira species from North America is limited. We evaluated the antimicrobial susceptibility profiles of U.S. Brachyspira isolates recovered between 2013 and 2022 to tiamulin, tylvalosin, lincomycin, doxycycline, bacitracin, and tylosin. In addition, we performed multilocus sequence typing (MLST) on 64 B. hyodysenteriae isolates. Overall, no distinct alterations in the susceptibility patterns over time were observed among Brachyspira species. However, resistance to the commonly used antimicrobials was seen sporadically with a higher resistance frequency to tylosin compared to other tested drugs. B. hampsonii was more susceptible to the tested drugs than B. hyodysenteriae and B. pilosicoli. MLST revealed 16 different sequence types (STs) among the 64 B. hyodysenteriae isolates tested, of which 5 STs were previously known, whereas 11 were novel. Most isolates belonged to the known STs: ST93 (n = 32) and ST107 (n = 13). Our findings indicate an overall low prevalence of resistance to clinically important antimicrobials other than tylosin and bacitracin, and high genetic diversity among the clinical Brachyspira isolates from pigs in the United States during the past decade. Further molecular, epidemiologic, and surveillance studies are needed to better understand the infection dynamics of Brachyspira on swine farms and to help develop effective control measures.

First molecular detection of Brachyspira suanatina on pig farms in Poland.

Introduction: Prior to the 2000s, swine dysentery was considered to be caused only by Brachyspira hyodysenteriae with contributing commensal intestinal anaerobes. Nowadays, it is known that the disease is caused by three strongly beta-haemolytic species of the anaerobic spirochaetal genus Brachyspira, i.e. B. hyodysenteriae and newly emerged B. hampsonii and B. suanatina. Material and Methods: The present investigation was carried out in November 2022 on nine Polish high-performing finisher pig farms. At every location one fresh pooled faecal sample was collected from 40 randomly selected pigs of between 60 and 110 kg live weight. Nucleic acid extracted from each pooled faecal sample was analysed by an in-house multiplex PCR for Brachyspira spp., which is capable of confirming the Brachyspira genus and detecting and differentiating Brachyspira species. Results: From a total of nine samples examined, the genetic material of B. suanatina was detected in seven. Non-pathogenic/questionably pathogenic Brachyspira spp. were found in six samples. Conclusion: To the best of our knowledge, this is the first report on the identification of B. suanatina in pigs outside Scandinavia, Germany and the United Kingdom. Our research not only provides valuable epidemiological data on B. suanatina infection in Europe but also highlights both the importance of modern laboratory diagnostics and the need for thorough investigation across regions, including retrospective studies.

Synergic Effect of Brachyspira hyodysenteriae and Lawsonia intracellularis Coinfection: Anatomopathological and Microbiome Evaluation.

Brachyspira hyodysenteriae and Lawsonia intracellularis coinfection has been observed in the diagnostic routine; however, no studies have evaluated their interaction. This study aimed to characterize lesions and possible synergisms in experimentally infected pigs. Four groups of piglets, coinfection (CO), B. hyodysenteriae (BRA), L. intracellularis (LAW), and negative control (NEG), were used. Clinical signals were evaluated, and fecal samples were collected for qPCR. At 21 days post infection (dpi), all animals were euthanized. Gross lesions, bacterial isolation, histopathology, immunohistochemistry, and fecal microbiome analyses were performed. Diarrhea started at 12 dpi, affecting 11/12 pigs in the CO group and 5/11 pigs in the BRA group. Histopathological lesions were significantly more severe in the CO than the other groups. B. hyodysenteriae was isolated from 11/12 pigs in CO and 5/11 BRA groups. Pigs started shedding L. intracellularis at 3 dpi, and all inoculated pigs tested positive on day 21. A total of 10/12 CO and 7/11 BRA animals tested positive for B. hyodysenteriae by qPCR. A relatively low abundance of microbiota was observed in the CO group. Clinical signs and macroscopic and microscopic lesions were significantly more severe in the CO group compared to the other groups. The presence of L. intracellularis in the CO group increased the severity of swine dysentery.

Prevalence and risk factors of Brachyspira spp. in pig herds with a history of diarrhoea in six European countries.

Swine dysentery and porcine intestinal spirochaetosis caused by Brachyspira (B.) hyodysenteriae and B. pilosicoli, respectively, are important diseases in swine production worldwide. The aim of this study was to assess the prevalence of both pathogens in farms with a history of diarrhoea within the last 12 months in Denmark, France, Germany, the Netherlands, Spain, and United Kingdom. In addition, risk factors for their prevalence and correlations between presence of different Brachyspira spp. and Lawsonia intracellularis were investigated. Therefore, faecal samples of 6355 nursery to finishing pigs out of 144 herds were sampled in 2017/2018 during a prevalence study on Lawsonia intracellularis, followed by polymerase chain reaction analysis for Brachyspira spp. detection. Herd prevalence differed significantly between countries, from 4.2% to 45.8% for B. hyodysenteriae and 8.3-87.5% for B. pilosicoli, respectively (p < 0.01). For the within-herd prevalence (in positive herds), these values ranged from 2.2% to 27.0% for B. hyodysenteriae and 3.3-50.8% for B. pilosicoli. Mixed infections occurred in 34.1% and 58.7% of B. hyodysenteriae positive samples with Lawsonia intracellularis or B. pilosicoli, respectively. In 43.2% of B. pilosicoli positive samples, Lawsonia intracellularis was detected simultaneously. Overall, nursery pigs were significantly less often positive for one of the pathogens than growing or finishing pigs (p < 0.001). The absence of gastrointestinal problems like diarrhoea, routine use of antimicrobials and well performed biosecurity measures were some of the factors associated with lower detection rate of Brachyspira spp. Surprisingly, deworming of different age categories also showed associations with the detection of Brachyspira spp. which, however, were not always equally directed, and therefore require further investigations. The only risk factor significant for both Brachyspira spp. was the median number of ≥ 30 nursery pigs per pen after weaning, compared to smaller group sizes. Both pathogens were detected with varying frequency between the six European countries. This should be considered in the probability of disease and in case of transnational transport, to prevent spread of pathogens. In addition, the frequent presence of mixed infections in some countries should be taken into account in diagnostics. The most important protective factors against Brachyspira spp. presence on farm are biosecurity measures, while potential new factors such as deworming still require further investigation.

Predictive Power of Long-Read Whole-Genome Sequencing for Rapid Diagnostics of Multidrug-Resistant Brachyspira hyodysenteriae Strains.

Infections with Brachyspira hyodysenteriae, the etiological agent of swine dysentery, result in major economic losses in the pig industry worldwide. Even though microbial differentiation of various Brachyspira species can be obtained via PCR, no quick diagnostics for antimicrobial susceptibility testing are in place, which is mainly due to the time-consuming (4 to 7 days) anaerobic growth requirements of these organisms. Veterinarians often rely on a clinical diagnosis for initiating antimicrobial treatment. These treatments are not always effective, which may be due to high levels of acquired resistance in B. hyodysenteriae field isolates. By using long-read-only whole-genome sequencing and a custom-trained Bonito base-calling model, 81 complete B. hyodysenteriae genomes with median Q51 scores and 99% completeness were obtained from 86 field strains. This allowed the assessment of the predictive potential of genetic markers in relation to the observed acquired resistance phenotypes obtained via agar dilution susceptibility testing. Multidrug resistance was observed in 77% and 21% of the tested strains based on epidemiological cutoff and clinical breakpoint values, respectively. The predictive power of genetic hallmarks (genes and/or gene mutations) for antimicrobial susceptibility testing was promising. Sensitivity and specificity for tiamulin [tva(A) and 50SL3N148S, 99% and 67%], valnemulin [tva(A), 97% and 92%), lincomycin (23SA2153T/G and lnuC, 94% and 100%), tylvalosin (23SA2153T/G, 99% and 93%), and doxycycline (16SG1026C, 93% and 87%) were determined. The predictive power of these genetic hallmarks is promising for use in sequencing-based workflows to speed up swine dysentery diagnostics in veterinary medicine and determine proper antimicrobial use. IMPORTANCE Diagnostics for swine dysentery rely on the identification of Brachyspira species using molecular techniques. Nevertheless, no quick diagnostic tools are available for antimicrobial susceptibility testing due to extended growth requirements (7 to 14 days). To enable practitioners to tailor antimicrobial treatment to specific strains, long-read sequencing-based methods are expected to lead to rapid methods in the future. Nevertheless, their potential implementation should be validated extensively. This mainly implies assessing sequencing accuracy and the predictive power of genetic hallmarks in relation to their observed (multi)resistance phenotypes.

In vitro evaluation of gentamicin activity against Spanish field isolates of Brachyspira hyodysenteriae.

BACKGROUND: The treatment of swine dysentery (SD) has become constrained in recent years due to the limited availability of effective drugs combined with a rise in antimicrobial resistance. Gentamicin, an aminoglycoside antibiotic, is authorised for the control of this disease in several European countries but has not been extensively used so far. In this study, the in vitro susceptibility of 56 Brachyspira hyodysenteriae field isolates was evaluated against gentamicin using a broth microdilution test. The molecular basis of decreased susceptibility to gentamicin was also investigated by sequencing the 16S rRNA gene and phylogenetic relatedness by multiple-locus variable number tandem-repeat analysis (MLVA). RESULTS: Most B. hyodysenteriae isolates presented low minimum inhibitory concentration (MIC) values to gentamicin, with a mode of 2 µg/mL, a median or MIC50 of 4 µg/mL and percentile 90 or MIC90 of 16 µg/mL. The distribution of these values over the period studied (2011-2019) did not show a tendency towards the development of resistance to gentamicin. Differences in susceptibility among isolates could be explained by two point-mutations in the 16S rRNA gene, C990T and A1185G, which were only present in isolates with high MICs. These isolates were typed in three different MLVA clusters. Analyses of co-resistance between gentamicin and antimicrobials commonly used for the treatment of SD revealed that resistance to tiamulin and valnemulin was associated with low MICs for gentamicin. CONCLUSIONS: The results provide an accurate characterisation of antimicrobial sensitivity to gentamicin and possible mechanisms of resistance in Spanish B. hyodysenteriae isolates. These findings allow us to propose gentamicin as an alternative in the antibiotic management of SD, particularly in outbreaks caused by pleuromutilin resistant isolates.

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 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.

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.

Swine dysentery is a severe disease that can cause increased mortality and poor feed efficiency with bloody diarrhea. This disease can be treated with antibiotics, but there is a limitation of using antibiotics due to governmental policy, thereby the incidence of swine dysentery has been increased. We, therefore, try to find alternatives with diverse fiber sources and understand the mechanism of swine dysentery in growing pigs. In this study, infection of Brachyspira hyodysenteriae showed a negative influence on growth performance, but compensatory growth and recovery were observed in pigs after 6 wk of the infection. The apparent ileal digestibility was not affected by the infection, and the digestibility of non-starch polysaccharides in the cecum was rather increased than decreased probably because of interaction between B. hyodysenteriae and specific bacteria, which can stimulate fiber degradation in the cecum. However, fiber type and level did not influence the prevention and alleviation of the infection.

Dual Antimicrobial Effect of Medium-Chain Fatty Acids against an Italian Multidrug Resistant Brachyspira hyodysenteriae Strain.

The fastidious nature of Brachyspira hyodysenteriae limits an accurate in vitro pre-screening of conventionally used antibiotics and other candidate alternative antimicrobials. This results in a non-judicious use of antibiotics, leading to an exponential increase of the antibiotic resistance issue and a slowdown in the research for new molecules that might stop this serious phenomenon. In this study we tested four antibiotics (tylosin, lincomycin, doxycycline, and tiamulin) and medium-chain fatty acids (MCFA; hexanoic, octanoic, decanoic, and dodecanoic acid) against an Italian field strain of B. hyodysenteriae and the ATCC 27164 strain as reference. We determined the minimal inhibitory concentrations of these substances, underlining the multidrug resistance pattern of the field strain and, on the contrary, a consistent and stable inhibitory effect of the tested MCFA against both strains. Then, sub-inhibitory concentrations of antibiotics and MCFA were examined in modulating a panel of B. hyodysenteriae virulence genes (tlyA, tlyB, bhlp16, bhlp29.7, and bhmp39f). Results of gene expression analysis were variable, with up- and downregulations not properly correlated with particular substances or target genes. Decanoic and dodecanoic acid with their direct and indirect antimicrobial property were the most effective among MCFA, suggesting them as good candidates for subsequent in vivo trials.

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

BACKGROUND: Brachyspira (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. RESULTS: The 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. CONCLUSIONS: This 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.

Combined in-vitro and on-farm evaluation of commercial disinfectants used against Brachyspira hyodysenteriae.

BACKGROUND: Swine dysentery (SD) is a severe infectious disease with a relevant impact on pig production usually caused by Brachyspira hyodysenteriae, although B. hampsonii causes an identical clinical picture. SD control relies on antimicrobials, good management practices and strict biosecurity with cleaning and disinfection as crucial tools to avoid the pathogen transmission. This study evaluates the in-vitro efficacy of an array of commercial disinfectants against a collection of B. hyodysenteriae isolates using broth tests. The efficacy of cleaning and disinfection protocols was also evaluated on two farms with endemic SD using surface swabs collected in emptied pens before and after cleaning and disinfection procedures, using both real-time PCR and bacterial microbiological culture. RESULTS: Most of the commercial disinfectants evaluated were effective against all B. hyodysenteriae isolates tested, with a reduction of more than 5.00 log10 CFU/mL (bactericidal efficacy of 99.999%). However, some isolates exhibited reduced susceptibility to Virkon-S and Limoseptic disinfectants. The evaluation of cleaning and disinfection protocols on farms with SD outbreaks showed that approximately half the pens tested (n = 25) were positive by real-time PCR after pigs removal (mean B. hyodysenteriae counts 5.72 ± 1.04 log10 CFU/mL) while almost 20% of the pens remained positive after cleaning (n = 7) and disinfection (n = 5) procedures although with significantly lower, mean estimates (4.31 ± 0.43 log10 CFU/mL and 4.01 ± 0.55 log10 CFU/mL, respectively). CONCLUSIONS: These results show the efficacy of disinfectants against B. hyodysenteriae but also stress the need to implement adequately the cleaning and disinfection protocols on pig farms and review and revise their efficiency periodically.

Acute infection with Brachyspira hyodysenteriae affects mucin expression, glycosylation, and fecal MUC5AC.

Introduction: Infection with strongly ß-hemolytic strains of Brachyspira hyodysenteriae leads to swine dysentery (SD), a production-limiting disease that causes mucohemorrhagic diarrhea and typhlocolitis in pigs. This pathogen has strong chemotactic activity toward mucin, and infected pigs often have a disorganized mucus layer and marked de novo expression of MUC5AC, which is not constitutively expressed in the colon. It has been shown that fucose is chemoattractant for B. hyodysenteriae, and a highly fermentable fiber diet can mitigate and delay the onset of SD. Methods: We used lectins targeting sialic acids in α-2,6 or α-2,3 linkages, N-acetylglucosamine (GlcNAc), α-linked L-fucose, and an immunohistochemical stain targeting N-glycolylneuraminic acid (NeuGc) to investigate the local expression of these mucin glycans in colonic tissues of pigs with acute SD. We used a commercial enzyme-linked immunosorbent assay (ELISA) to quantify fecal MUC5AC in infected pigs and assess its potential as a diagnostic monitoring tool and RNA in situ hybridization to detect IL-17A in the colonic mucosa. Results: Colonic mucin glycosylation during SD has an overall increase in fucose, a spatially different distribution of GlcNAc with more expression within the crypt lumens of the upper colonic mucosa, and decreased expression or a decreased trend of sialic acids in α-2,6 or α-2,3 linkages, and NeuGc compared to the controls. The degree of increased fucosylation was less in the colonic mucosa of pigs with SD and fed the highly fermentable fiber diet. There was a significant increase in MUC5AC in fecal and colonic samples of pigs with SD at the endpoint compared to the controls, but the predictive value for disease progression was limited. Discussion: Fucosylation and the impact of dietary fiber may play important roles in the pathogenesis of SD. The lack of predictive value for fecal MUC5AC quantification by ELISA is possibly due to the presence of other non-colonic sources of MUC5AC in the feces. The moderate correlation between IL-17A, neutrophils and MUC5AC confirms its immunoregulatory and mucin stimulatory role. Our study characterizes local alteration of mucin glycosylation in the colonic mucosa of pigs with SD after B. hyodysenteriae infection and may provide insight into host-pathogen interaction.

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.

Implementation and evaluation of different eradication strategies for Brachyspira hyodysenteriae.

BACKGROUND: Brachyspira infections are causing major losses to the pig industry and lead to high antimicrobial use. Treatment of Brachyspira (B.) hyodysenteriae infections may be problematic due to the high level of antimicrobial resistance. The present study implemented and evaluated farm-specific eradication programmes for B. hyodysenteriae in 10 different infected pig farms in Belgium. RESULTS: Ten pig farms clinically infected with B. hyodysenteriae volunteered to implement a farm-specific eradication programme. The programme depended on the farm and management characteristics, antimicrobial susceptibility of the B. hyodysenteriae strain and the motivation of the farmer. Two farms practiced total depopulation, six farms partial depopulation and two farms antimicrobial medication without depopulation. In addition, all farms implemented biosecurity measures, and faeces samples were tested for the presence of B. hyodysenteriae at 6, 9 and 12 months after the start of the program. Single Brachyspira isolates from before and after the programme were typed using multilocus sequence typing (MLST).Eradication was successful in four farms. Two of them (farrow-to-finish and finishing herd) had applied total depopulation and respected a vacancy period of at least 3 weeks. A third farm (gilt farm) practised partial depopulation, the rooms remained empty for 28 days and changed the source of breeding gilts. The fourth farm practised partial depopulation, the stables remained empty for 3 weeks, and used antimicrobial medication. The eradication programme was not successful in six farms. Two of the latter farms only used medication without partial depopulation. Four farms practiced partial depopulation, one of them combined it with antimicrobial medication. The cleaning and disinfection procedures, rodent control, stand-empty period and/or other biosecurity measures in the six farms were not always implemented properly. In two of three farms, isolates belonging to the same MLST type were found before and after eradication. CONCLUSIONS: Total depopulation or partial depopulation combined with implementing strict biosecurity measures allowed eradication of B. hyodysenteriae from clinically infected pig farms. Programmes based on antimicrobials without depopulation or partial depopulation without strictly adhering to all suggested biosecurity measures were not successful. Stockmanship and motivation of the farmer to permanently maintain high biosecurity standards are essential for success.

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.