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.

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

BACKGROUND: Swine 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. RESULTS: Strongly 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. CONCLUSION: Our 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.

The tva(A) Gene from Brachyspira hyodysenteriae Confers Decreased Susceptibility to Pleuromutilins and Streptogramin A in Escherichia coli.

The tva(A) gene suspected to confer resistance to pleuromutilins in Brachyspira hyodysenteriae was tested for functionality in Escherichia coli AG100A and Staphylococcus aureus RN4220. Expression of the cloned tva(A) gene conferred decreased susceptibility to pleuromutilin (P) and streptogramin A (SA) antibiotics in E. coli and had a minor effect in S. aureus The finding provides evidence of the direct association of tva(A) with the PSA resistance phenotype.

An atypical weakly haemolytic strain of Brachyspira hyodysenteriae is avirulent and can be used to protect pigs from developing swine dysentery.

The anaerobic intestinal spirochaete Brachyspira hyodysenteriae colonises the large intestine of pigs and causes swine dysentery (SD), a severe mucohaemorrhagic colitis. SD occurs worldwide, and control is hampered by a lack of vaccines and increasing antimicrobial resistance. B. hyodysenteriae strains typically produce strong beta-haemolysis on blood agar, and the haemolytic activity is thought to contribute to the pathogenesis of SD. Recently, weakly haemolytic variants of B. hyodysenteriae have been identified in Europe and Australia, and weakly haemolytic strain D28 from Belgium failed to cause disease when used experimentally to infect pigs. Moreover, pigs colonised with D28 and then challenged with virulent strongly haemolytic strain B204 showed a delay of 2-4 days in developing SD compared to pigs not exposed to D28. The current study aimed to determine whether Australian weakly haemolytic B. hyodysenteriae strain MU1, which is genetically distinct from D28, could cause disease and whether exposure to it protected pigs from subsequent challenge with strongly haemolytic virulent strains. Three experimental infection studies were undertaken in which no diseases occurred in 34 pigs inoculated with MU1, although mild superficial lesions were found in the colon in 2 pigs in one experiment. In two experiments, significantly fewer pigs exposed to MU1 and then challenged with strongly haemolytic virulent strains of B. hyodysenteriae developed SD compared to control pigs not previously exposed to MU1 (p = 0.009 and p = 0.0006). These data indicate that MU1 lacks virulence and has potential to be used to help protect pigs from SD.

Weakly haemolytic variants of Brachyspira hyodysenteriae newly emerged in Europe belong to a distinct subclade with unique genetic properties.

Brachyspira (B.) hyodysenteriae is widespread globally, and can cause mucohaemorrhagic colitis (swine dysentery, SD) with severe economic impact in infected herds. Typical strains of B. hyodysenteriae are strongly haemolytic on blood agar, and the haemolytic activity is believed to contribute to virulence in vivo. However, recently there have been reports of atypical weakly haemolytic isolates of B. hyodysenteriae (whBh). In this study, 34 European whBh and 82 strongly haemolytic isolates were subjected to comparative genomic analysis. A phylogenetic tree constructed using core single nucleotide polymorphisms showed that the whBh formed a distinct sub-clade. All eight genes previously associated with haemolysis in B. hyodysenteriae were present in the whBh. No consistent patterns of amino acid substitutions for all whBh were found in these genes. In contrast, a genome region containing six coding sequences (CDSs) had consistent nucleotide sequence differences between strongly and whBh isolates. Two CDSs were predicted to encode ABC transporter proteins, and a TolC family protein, which may have a role in the export of haemolysins from B. hyodysenteriae. Another difference in this region was the presence of three CDSs in whBh that are pseudogenes in strongly haemolytic isolates. One of the intact CDSs from whBh encoded a predicted PadR-like transcriptional repressor that may play a role in repression of haemolysis functions. In summary, a sub-clade of whBh isolates has emerged in Europe, and several genomic differences, that potentially explain the weakly haemolytic phenotype, were identified. These markers may provide targets for discriminatory molecular tests needed in SD surveillance.

The role of transportation in the spread of Brachyspira hyodysenteriae in fattening farms.

BACKGROUND: Direct and indirect contact among animals and holdings are important in the spread of Brachyspira hyodysenteriae. The objective of this study was to investigate the role of slaughterhouse vehicles in spreading B. hyodysenteriae between unconnected farms. RESULTS: Multilocus sequence typing (MLST) and Multiple Locus Variable number tandem repeat Analysis (MLVA) were used to characterize B. hyodysenteriae strains isolated from trucks. Before cleaning, 976 batches of finishing pigs transported by 174 trucks from 540 herds were sampled. After cleaning, 763 of the 976 batches were also sampled. Sixty-one of 976 and 4 of 763 environmental swabs collected from trucks before and after cleaning and disinfection operations, respectively, were positive for B. hyodysenteriae. The 65 isolates in this study originated from 48 farms. Trucks were classified into five categories based on the number of visited farms as follows: category 1: 1-5 farms, category 2: 6-10 farms, category 3: 11-15 farms, category 4: 16-20 farms, category 5: >21 farms. Although the largest number of vehicles examined belonged to category 1, the highest percentage of vehicles positive for B. hyodysenteriae was observed in categories 3, 4 and 5. Specifically, 90.9% of trucks belonging to category 5 were positive for B. hyodysenteriae, followed by categories 4 and 3 with 85.7% and 83.3%, respectively. The results of MLST and MLVA suggest that trucks transporting pigs from a high number of farms also play a critical role in spreading different B. hyodysenteriae genetic profiles. STVT 83-3, which seems to be the current dominant type in Italy, was identified in 56.25% of genotyped isolates. The genetic diversity of isolated strains from trucks was high, particularly, in truck categories 3, 4 and 5. This result confirmed that MLST and MLVA can support the study of epidemiological links between different B. hyodysenteriae farm strains. CONCLUSIONS: This study highlights the potential role of shipments in B. hyodysenteriae spread. Moreover, it emphasizes the importance of strict vehicle hygiene practices for biosecurity programmes.

Brachyspira hyodysenteriae Infection Regulates Mucin Glycosylation Synthesis Inducing an Increased Expression of Core-2 O-Glycans in Porcine Colon.

Brachyspira hyodysenteriae causes swine dysentery (SD), leading to global financial losses to the pig industry. Infection with this pathogen results in an increase in B. hyodysenteriae binding sites on mucins, along with increased colonic mucin secretion. We predict that B. hyodysenteriae modifies the glycosylation pattern of the porcine intestinal mucus layer to optimize its host niche. We characterized the swine colonic mucin O-glycome and identified the differences in glycosylation between B. hyodysenteriae-infected and noninfected pigs. O-Glycans were chemically released from soluble and insoluble mucins isolated from five infected and five healthy colon tissues and analyzed using porous graphitized carbon liquid chromatography tandem mass spectrometry. In total, 94 O-glycans were identified, with healthy pigs having higher interindividual variation, although a larger array of glycan structures was present in infected pigs. This implied that infection induced loss of individual variation and that specific infection-related glycans were induced. The dominating structures shifted from core-4-type O-glycans in noninfected pigs toward core-2-type O-glycans in infected animals, which correlated with increased levels of the C2GnT glycosyl transferase. Overall, glycan chains from infected pigs were shorter and had a higher abundance of structures that were neutral or predominantly contained NeuGc instead of NeuAc, whereas they had a lower abundance of structures that were fucosylated, acidic, or sulfated than those from noninfected pigs. Therefore, we conclude that B. hyodysenteriae plays a major role in regulating colonic mucin glycosylation in pigs during SD. The changes in mucin O-glycosylation thus resulted in a glycan fingerprint in porcine colonic mucus that may provide increased exposure of epitopes important for host-pathogen interactions. The results from this study provide potential therapeutic targets and a platform for investigations of B. hyodysenteriae interactions with the host via mucin glycans.

Characterization of Brachyspira hyodysenteriae isolates from Italy by multilocus sequence typing and multiple locus variable number tandem repeat analysis.

AIMS: To evaluate and compare the capabilities of multilocus sequence typing (MLST) and multiple locus variable number tandem repeat analysis (MLVA) techniques to characterize Brachyspira hyodysenteriae isolates and to investigate the relationship between pleuromutilin resistance and genetic variability. METHODS AND RESULTS: MLST genotyping was performed on 180 B. hyodysenteriae isolates, and the results were evaluated considering profiles from 108 other strains previously reported in the database. In total, 37 sequence types were obtained. The MLVA approach completely characterized 172 strains and grouped the isolates into 22 different profiles. The combination of MLST and MLVA showed a slight increase in the discriminatory power, identifying 33 joint profiles. An antibiotic resistance analysis showed a reduction in the susceptibility to pleuromutilins over time, and a weak association between susceptibility to valnemulin and inclusion in clonal complex 4. CONCLUSION: MLST and MLVA are reliable methods for characterizing B. hyodysenteriae strains and they have comparable discriminatory power. SIGNIFICANCE AND IMPACT OF THE STUDY: The genotyping of B. hyodysenteriae isolates and a database of all the genetic profiles collected during the diagnostic activities could support traditional epidemiological investigations in identifying infection sources and routes of transmission among herds, and in developing more effective control measures.

Variation in hemolytic activity of Brachyspira hyodysenteriae strains from pigs.

Brachyspira hyodysenteriae is the primary cause of swine dysentery, which is responsible for major economic losses to the pig industry worldwide. The hemolytic activity of 10 B. hyodysenteriae strains isolated from stools of pigs with mild to mucohemorrhagic diarrhea was compared and seven hemolysis associated genes were sequenced. Hemolysis induced by these strains varied from strong to near absent. One weakly hemolytic B. hyodysenteriae strain showed sequence changes in five hemolysis associated genes (tlyA, tlyB, hemolysin III, hemolysin activation protein and hemolysin III channel protein) resulting in amino acid substitutions. The occurrence of weakly hemolytic strains identifiable as B. hyodysenteriae should be taken into account in swine dysentery diagnostics. The presence of these strains may affect herd dysentery status, with great impact on a farms trading opportunities.

Absence of a set of plasmid-encoded genes is predictive of reduced pathogenic potential in Brachyspira hyodysenteriae.

The gene content of 14 strains of the intestinal spirochaete Brachyspira hyodysenteriae was compared using a DNA microarray. A consistent difference occurred in a block of four genes on the ~36 Kb plasmid, with these being present in six virulent strains and absent in eight strains with reduced pathogenic potential. These genes encoded a predicted radical S-adenosylmethionine domain protein, a glycosyl transferase group 1-like protein, an NAD dependent epimerase and a dTDP-4-dehydrorhamnose 2-5 epimerase: they may be involved in rhamnose biosynthesis and glycosylation. The absence of these plasmid genes in B. hyodysenteriae isolates is predictive of reduced pathogenic potential.

Comparison of sesion severity, distribution, and colonic mucin expression in pigs with acute swine dysentery following oral inoculation with "Brachyspira hampsonii" or Brachyspira hyodysenteriae.

Swine dysentery is classically associated with infection by Brachyspira hyodysenteriae, the only current officially recognized Brachyspira sp. that consistently imparts strong beta-hemolysis on blood agar. Recently, several strongly beta-hemolytic Brachyspira have been isolated from swine with clinical dysentery that are not identified as B. hyodysenteriae by PCR including the recently proposed species "Brachyspira hampsonii." In this study, 6-week-old pigs were inoculated with either a clinical isolate of "B. hampsonii" (EB107; n = 10) clade II or a classic strain of B. hyodysenteriae (B204; n = 10) to compare gross and microscopic lesions and alterations in colonic mucin expression in pigs with clinical disease versus controls (n = 6). Gross lesions were similar between infected groups. No histologic difference was observed between infected groups with regard to neutrophilic inflammation, colonic crypt depth, mucosal ulceration, or hemorrhage. Histochemical and immunohistochemical evaluation of the apex of the spiral colon revealed decreased expression of sulphated mucins, decreased expression of MUC4, and increased expression of MUC5AC in diseased pigs compared to controls. No difference was observed between diseased pigs in inoculated groups. This study reveals significant alterations in colonic mucin expression in pigs with acute swine dysentery and further reveals that these and other microscopic changes are similar following infection with "B. hampsonii" clade II or B. hyodysenteriae.

In vitro susceptibility of Brachyspira hyodysenteriae strains isolated in pigs in northern Italy between 2005 and 2022.

Pleuromutilins (tiamulin and valnemulin) are often used to treat swine dysentery due to recurrent resistance to macrolides and lincosamides. Recently, reduced susceptibility of B. hyodysenteriae to pleuromutilin has been reported. 536 strains of B. hyodysenteriae were isolated from symptomatic pigs weighing 30-150 kg in northern Italy between 2005 and 2022. B. hyodysenteriae was isolated by standard methods and confirmed by PCR. The minimum inhibitory concentration (MIC) to doxycycline, lincomycin, tiamulin, tylosin, tylvalosine and valnemulin was evaluated according to CLSI procedures and MIC data were reported as MIC 50 and MIC 90. The temporal trend of the MIC values was evaluated by dividing the data into two groups (2005-2013 and 2014-2022). Comparison of the distribution in frequency classes in the two periods was performed using Pearson's chi-squared test (p < 0.01). MIC 50 was close to the highest values tested for lincomycin and tylosin, while MIC 90 was close to the highest values tested for all antibiotics. 71.7% of the strains were susceptible to tylvalosin, while 75%-80.4% had reduced susceptibility to valnemulin and tiamulin, respectively. The difference in the distribution of MIC classes was statistically significant in the two periods for doxycycline, tiamulin, tylvalosin and valnemulin, and more MIC classes above the epidemiological cut-off were observed in 2014-2022 compared with 2005-2013. The evaluation of the trends during the period considered shows a decreasing rate of wild-type strains with MIC values below the epidemiological cut-off over time and confirms the presence of resistant strains in northern Italy.

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.

Adherence of Brachyspira hyodysenteriae to porcine intestinal epithelial cells is inhibited by antibodies against outer membrane proteins.

Attachment of Brachyspira hyodysenteriae to intestinal epithelial cell lines and its possible mediation by outer membrane proteins (OMPs) of the spirochete were examined. Different B. hyodysenteriae serotypes were shown to adhere to rat and swine intestinal epithelial cells (IEC-18 and IPEC-J2) in vitro but not to the human rectal tumor cell line (HRT-18). Adherence of strain B204 to IPEC-J2 cells was reduced by rOMP-specific antisera in amounts of 29 % (anti-rBhlp29.7), 59 % (anti-rBhlp16), 70 % (anti-rBhmp39h), and 74 % (anti-rBhmp39h), respectively. By use of pooled antisera against Bhlp16 and Bhmp39f inhibition rates of the other serotypes ranged from 53 to 91 %. In a western blot assay OMPs of all serotypes but one were detected by the respective rOMP antisera. Altogether the results indicated that OMPs of B. hyodysenteriae displayed a serotype overlapping antigenicity and mediated adherence of the spirochetes to animal cell cultures.

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.

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.

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.

Trends towards lower antimicrobial susceptibility and characterization of acquired resistance among clinical isolates of Brachyspira hyodysenteriae in Spain.

The antimicrobial susceptibility of clinical isolates of Brachyspira hyodysenteriae in Spain was monitored, and the underlying molecular mechanisms of resistance were investigated. MICs of tylosin, tiamulin, valnemulin, lincomycin, and tylvalosin were determined for 87 B. hyodysenteriae isolates recovered from 2008 to 2009 by broth dilution. Domain V of the 23S rRNA gene and the ribosomal protein L3 gene were sequenced in 20 isolates for which the tiamulin MIC was ≥ 4 µg/ml, presenting decreased susceptibility, and in 18 tiamulin-susceptible isolates (MIC ≤ 0.125 µg/ml), and all isolates were typed by multiple-locus variable-number tandem repeats analysis. A comparison with antimicrobial susceptibility data from 2000 to 2007 showed an increase in pleuromutilin resistance over time, doubling the number of isolates with decreased susceptibility to tiamulin. No alteration in susceptibility was detected for lincomycin, and the MIC of tylosin remained high (MIC(50) > 128 µg/ml). The decreased susceptibility to tylosin and lincomycin can be explained by mutations at position A2058 of the 23S rRNA gene (Escherichia coli numbering). A2058T was the predominant mutation, but A2058G also was found together with a change of the neighboring base pair at positions 2057 to 2611. The role of additional point mutations in the vicinity of the peptidyl transferase center and mutations in the L3 at amino acids 148 and 149 and their possible involvement in antimicrobial susceptibility are considered. An association between G2032A and high levels of tiamulin and lincomycin MICs was found, suggesting an increasing importance of this mutation in antimicrobial resistance of clinical isolates of B. hyodysenteriae.

[Swine dysentery eradication in a grower-finisher farm in Switzerland]. / Die Sanierung der Schweinedysenterie in einem Schweizer Aufzucht-Mastbetrieb.

On a Swiss grower-finisher farm blood-tinged-diarrhoea in pigs weighing 40 to 60 kg was observed during several months, resulting in reduced feed efficiency and a prolonged fattening period. As part of a research project, in February 2007 faecal samples were analysed and one diseased pig was euthanised and sent for necropsy where typical gut lesions indicative for a Brachyspira (B.) hyodysenteriae infection were found. B. hyodysenteriae was demonstrated by PCR in 4 out of 5 faecal samples. The pig farm thereafter underwent an eradication process with timed depopulation of the consecutive pigpens. During February to June 2008 the farm was regularly inspected and tested for B. hyodysenterieae. Testing continued for another year after the eradication process and all faecal samples proved negative. Until January 2010 neither diarrhoea with blood nor B. hyodysenterieae reoccurred.

Brachyspira hyodysenteriae isolate multilocus sequence type dashboard.

This focus article has been prepared by Susanna Williamson, Emma Stubberfield and Anna Brzozowska of the APHA and Jill Thomson of SRUC - Veterinary Consulting Services, Edinburgh.