Differentiation of Serpulina species by NADH oxidase gene (nox) sequence comparisons and nox-based polymerase chain reaction tests

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.

Molecular characterization of antimicrobial resistance in Brachyspira species isolated from UK chickens: Identification of novel variants of pleuromutilin and beta-lactam resistance genes

Brachyspira species are Gram negative, anaerobic bacteria that colonise the gut of many animals, including poultry. In poultry, Brachyspira species can be commensal (B. innocens, B. murdochii, 'B. pulli') or pathogenic (B. pilosicoli, B. intermedia, B. alvinipulli or rarely B. hyodysenteriae), the latter causing avian intestinal spirochaetosis (AIS). Antimicrobial therapy options for treatment is limited, frequently involving administration of the pleuromutilin, tiamulin, in water. In this study 38 Brachyspira isolates from chickens in the UK, representing both commensal and pathogenic species, were whole genome sequenced to identify antimicrobial resistance (AMR) mechanisms and the minimum inhibitory concentration (MIC) to a number of antimicrobials was also determined. We identified several new variants of blaOXA in B. pilosicoli and B. pulli isolates, and variations in tva which led to two new tva variants in B.murdochii and B.pulli. A number of isolates also harboured mutations known to encode AMR in the 16S and 23S rRNA genes. The percentage of isolates that were genotypically multi-drug resistance (MDR) was 16%, with the most common resistance profile being: tetracycline, pleuromutilin and beta-lactam, which were found in three 'B. pulli' and one B. pilosicoli. There was good correlation with the genotype and the corresponding antibiotic MIC phenotypes: pleuromutilins (tiamulin and valnemulin), macrolides (tylosin and tylvalosin), lincomycin and doxycycline. The occurrence of resistance determinants identified in this study in pathogenic Brachyspira, especially those which were MDR, is likely to impact treatment of AIS and clearance of infections on farm.

Antimicrobial susceptibility of western Canadian Brachyspira isolates: Development and standardization of an agar dilution susceptibility test method

The re-emergence of Brachyspira-associated disease in pigs since the late 2000s has illuminated some of the diagnostic challenges associated with this genus; notably, the lack of standardized antimicrobial susceptibility testing (AST) methods and interpretive criteria. Consequently, laboratories have relied heavily on highly variable in-house developed methods. There are currently no published investigations describing the antimicrobial susceptibility of Brachyspira isolates collected from pigs in Canada. The first objective of this study was therefore to develop a standardized protocol for conducting agar dilution susceptibility testing of Brachyspira spp., including determining the optimal standardized inoculum density, a key test variable that impacts test performance. The second objective was to determine the susceptibility of a collection of western Canadian Brachyspira isolates using the standardized methodology. After assessing multiple media, an agar dilution test was standardized in terms of starting inoculum (1-2 × 108 CFU/ml), incubation temperature and time, and assessed for repeatability. The antimicrobial susceptibility of a collection of clinical porcine Brachyspira isolates (n = 87) collected between 2009-2016 was then determined. This method was highly reproducible; repeat susceptibility testing yielded identical results 92% of the time. Although most of the isolates had very low MICs to the commonly used antimicrobials to treat Brachyspira-associated infections, several isolates with elevated MICs (>32 μg/ml) for tiamulin, valnemulin, tylosin, tylvalosin, and lincomycin were identified. Overall, this study underscores the importance of establishing CLSI approved clinical breakpoints for Brachyspira to facilitate the interpretation of test results and support the evidence-based selection of antimicrobials in swine industry.

Cecal Reduction of Brachyspira and Lesion Severity in Laying Hens Supplemented with Fermented Defatted ‘Alperujo’

Antimicrobial resistance demands the development of therapeutic alternatives such as prebiotics, probiotics, and nutraceuticals. The aim of this study was to assess the antimicrobial proprieties of the nutraceutical fermented defatted “alperujo”, derived from olive oil production, in a laying hen farm (n = 122,250) endemic with avian intestinal spirochetosis (Brachyspira spp.). Part of the batch (n = 1440) was divided into six groups of 240 hens each that included 80 or 108-week-old laying hens, supplemented with 0%, 2%, or 6% fermented defatted ‘alperujo’ for a month. At the end of the experiment, eight hens from each group were autopsied and cecal content was subjected to (i) Brachyspira culture and species identification by PCRs, and (ii) direct DNA extraction and Brachyspira qPCR. Furthermore, the ceca were processed for histopathology. Microbiological isolation revealed B. pilosicoli and B. hyodysenteriae co-infection in all groups. The 80-week-old hen group 2% supplemented showed a reduction in the cecal Brachyspira content (qPCR) compared with non-supplemented hens. Cecal histopathology showed a diffuse mild infiltration of lymphocytes, plasma cells, and heterophils; and hyperplasia of the gut-associated lymphoid tissue hyperplasia which decreased in severity in 80-week-old supplemented hens. The reduction in Brachyspira colonization and the severity of the lesions observed in supplemented hens highlights a potential protective function against avian intestinal spirochetosis.

Novel multiplex TaqMan assay for differentiation of the four major pathogenic Brachyspira species in swine

A novel TaqMan 5-plex real-time PCR using a combination of locked nucleic acid-modified (LNA)- and minor groove binding (MGB)-conjugated DNA probes was developed for identification and differentiation between the four main pathogenic Brachyspira species in swine. B. hyodysenteriae, B. pilosicoli, and B. suanatina are identified using three hydrolysis probes targeting cpn60, while B. hampsonii is recognized by another nox specific probe. The assay also includes an exogenous internal control simultaneously verifying the PCR competency of the DNA samples. Validation of the novel assay was performed using DNA samples from 18 Brachyspira reference strains and 477 clinical samples obtained from porcine rectal swabs by comparing them with different PCR-based methods targeting nox, 16S rDNA, and 23S rDNA. The specificity of the assay was 100% without cross-reactivity or detection of different pathogens. Depending on the Brachyspira species, the limit of detection was between 10 and 20 genome equivalents with a cut-off threshold cycle (Ct) value of 37. The developed highly sensitive and specific 5-plex real-time PCR assay is easy to implement in routine veterinary diagnostic laboratories and enables rapid differentiation between the main four pathogenic Brachyspira species recognized in pigs using a single-tube approach.

Retrospective analysis of necrotizing typhlitis cases associated with Brachyspira spp. in British rheas

This paper describes a retrospective analysis of necrotizing typhlitis in common rheas (Rhea americana) diagnosed in the United Kingdom by the Animal & Plant Health Agency (APHA). From January 2008 to January 2020, seven cases of spirochaetal typhlitis associated with Brachyspira spp. were identified using the Veterinary Investigation Diagnosis Analysis database. Gross examination was combined with selective anaerobic culture, polymerase chain reaction, and histopathology to diagnose typhlitis associated with spirochaetal infection. Whole-genome sequencing was subsequently utilized on archived isolates from six of the seven submissions, overcoming issues with traditional testing methods and yielded gains in the identification of Brachyspira to species level. Brachyspira hyodysenteriae, an organism traditionally associated with typhlitis in rheas, was isolated in three sequenced submissions. One of these also demonstrated co-infection with Brachyspira intermedia. Brachyspira suanatina, Brachyspira hampsonii, and Brachyspira alvinipulli were identified by sequencing as single infections in the remaining three animals. This report demonstrates the ability of Brachyspira species other than B. hyodysenteriae to colonize the caeca of rheas presenting with typhlitis. Additionally, the B. alvinipulli isolate harboured a tva(A) gene, indicating higher potential pleuromutilin resistance, which has not previously been described in this Brachyspira species. This study discusses the epidemiology of examined cases and examines the potential role other species may play in these outbreaks.

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.

Identification of Brachyspira species by cpn60 universal target sequencing is superior to NADH oxidase gene sequencing

The pig colon is the habitat of diverse Brachyspira species, of which only a few are of clinical importance. Methods for identification have shifted from phenotypic to molecular testing over the last two decades. Following the emergence of B. hampsonii it became evident that relying on species-specific PCRs carries the risk of overlooking important new species. Consequently, sequencing was proposed as an unbiased alternative for identification of isolates. So far, the main target for identification across species has been the NADH oxidase gene (nox). However, multiple copies of this gene in the genome and potential lateral gene transfer reduce confidence when using this gene. This study compared identification and phylogentic relationship inferred from nox sequencing to that inferred from sequencing of the cpn60 universal target using a collection of 168 isolates from different Brachyspira species. The majority of isolates had an identical identification with both methods. There were a few outliers in the trees with uncertain assignment to a species by BLAST analysis. A few major discrepancies pertained to the pathogenic species B. hampsonii (2), B. pilosicoli (1) and B. suanatina (1). Weakly haemolytic variants of B. hyodysenteriae were assigned to the correct species by both methods. Some of the isolates identified as B. hampsonii also had a weakly haemolytic phenotype.

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.

Retrospective detection of Brachyspira hampsonii in archived colitis cases from western Canadian swine

Mucohaemorrhagic diarrhea associated with Brachyspira hampsonii infection has emerged as a production-limiting disease in western Canada. This pathogen was first described in North America in 2010, and reports of its detection occurred concurrently in western Canada and the United States. Since that time, Brachyspira hampsonii has been detected in Europe, both in pigs and in waterfowl. The origin of B. hampsonii and the timing and reasons for its emergence are unknown. We conducted a retrospective study of historic, archived cases of porcine colitis to determine when B. hampsonii was first evident in western Canada. A total of 206 samples from 114 cases submitted from 57 different farms or productions systems in 1984 and 1999-2009 were screened using real-time PCR assays targeting B. hampsonii genomovars I and II, and Brachyspira hyodysenteriae (the traditional agent of swine dysentery). In most cases, positive real-time PCR results were confirmed by amplification and sequencing of additional gene targets. A total of 9, 7 and 5 samples tested positive for B. hampsonii (I), B. hampsonii (II) or B. hyodysenteriae respectively. The results of this study push the date of first appearance of B. hampsonii in pigs in western Canada back to 2002 (B. hampsonii (I)) and 2006 (B. hampsonii (II)), which is up to 7 years before the new species were first identified in fresh samples.

Characterization of Brachyspira communities from clinical cases of swine mucohaemorrhagic diarrhea through deep sequencing of the NADH oxidase (nox) gene

Swine dysentery is traditionally associated with Brachyspira hyodysenteriae, but the re-emergence of Brachyspira-associated disease in North America associated with a novel causative species, B. hampsonii, is now a concern for swine producers. The pathogenesis of Brachyspira-associated disease is not completely understood, and it is not known whether mixed infections of Brachyspira spp. are important in disease development. Deep sequencing of partial sequences of the nox gene amplified with genus-specific primers was used to detect Brachyspira spp. in 55 fecal samples from clinical cases of mucohaemorrhagic diarrhea in pigs from Western Canada that had been identified as positive for one or more Brachyspira species using established diagnostic tests. Synthetic mixtures of Brachyspira genomic DNA were included in the study to define detection limits for the technique and identify biases in detection of different species. Multiple species were detected in all clinical cases for which sufficient nox sequence data were generated (n = 47), indicating that mixed species Brachyspira infections are common, although in most cases, one species accounted for at least half of the sequences identified. In all cases, the species detected in the original diagnostic investigation of each case was also detected by nox sequencing. Results from synthetic communities indicated that the method was highly reproducible, but also indicated potential PCR bias against B. hampsonii genomovar I. Deep sequencing of the nox gene target is a suitable method for simultaneous detection of multiple Brachyspira species in clinical case material that may offer advantages over current, more targeted diagnostic approaches for investigating the significance of mixed infections in disease development.

The Spirochete Brachyspira pilosicoli, Enteric Pathogen of Animals and Humans

Brachyspira pilosicoli is a slow-growing anaerobic spirochete that colonizes the large intestine. Colonization occurs commonly in pigs and adult chickens, causing colitis/typhlitis, diarrhea, poor growth rates, and reduced production. Colonization of humans also is common in some populations (individuals living in village and peri-urban settings in developing countries, recent immigrants from developing countries, homosexual males, and HIV-positive patients), but the spirochete rarely is investigated as a potential human enteric pathogen. In part this is due to its slow growth and specialized growth requirements, meaning that it is not detectable in human fecal samples using routine diagnostic methods. Nevertheless, it has been identified histologically attached to the colon and rectum in patients with conditions such as chronic diarrhea, rectal bleeding, and/or nonspecific abdominal discomfort, and one survey of Australian Aboriginal children showed that colonization was significantly associated with failure to thrive. B. pilosicoli has been detected in the bloodstream of elderly patients or individuals with chronic conditions such as alcoholism and malignancies. This review describes the spirochete and associated diseases. It aims to encourage clinicians and clinical microbiologists to consider B. pilosicoli in their differential diagnoses and to develop and use appropriate diagnostic protocols to identify the spirochete in clinical specimens.

Minimum inhibitory concentration of Brazilian Brachyspira hyodysenteriae strains

ABSTRACT: The objectives of this study were to characterize Brachyspira hyodysenteriae isolates and to evaluate the antimicrobial susceptibility patterns of strains obtained from pigs in Brazil based on the minimal inhibitory concentration test (MIC). The MIC was performed for 22 B. hyodysenteriae isolates obtained from 2011 to 2013 using the following antimicrobial drugs: tylosin, tiamulin, valnemulin, doxycycline, lincomycin and tylvalosin. Outbreaks of swine dysentery were diagnosed based on clinical presentation, bacterial isolation, gross and microscopic lesions, duplex PCR for B. hyodysenteriae and B. pilosicoli and nox gene sequencing. All obtained MIC values were consistently higher or equal to the microbiological cut-off described in the literature. The MIC 90 values for the tested drugs were 8μg/ml for doxycycline, >4μg/ml for valnemulin, 8μg/ml for tiamulin, 32μg/ml for tylvalosin, >64μg/ml for lincomycin and >128μg/ml for tylosin. These results largely corroborate those reported in the literature. Tiamulin, doxycycline and tylvalosin showed the lowest MIC results. All of the samples subjected to phylogenetic analysis based on the nox gene sequence exhibited similar results, showing 100% identity to B. hyodysenteriae. This is the first study describing the MIC pattern of B. hyodysenteriae isolated in Brazil.

Characterization and Recognition of Brachyspira hampsonii sp. nov., a Novel Intestinal Spirochete That Is Pathogenic to Pigs

Swine dysentery (SD) is a mucohemorrhagic colitis of swine classically caused by infection with the intestinal spirochete Brachyspira hyodysenteriae Since around 2007, cases of SD have occurred in North America associated with a different strongly beta-hemolytic spirochete that has been molecularly and phenotypically characterized and provisionally named "Brachyspira hampsonii." Despite increasing international interest, B. hampsonii is currently not recognized as a valid species. To support its recognition, we sequenced the genomes of strains NSH-16T, NSH-24, and P280/1, representing B. hampsonii genetic groups I, II, and III, respectively, and compared them with genomes of other valid Brachyspira species. The draft genome of strain NSH-16T has a DNA G+C content of 27.4% and an approximate size of 3.2 Mb. Genomic indices, including digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI), and average amino acid identity (AAI), clearly differentiated B. hampsonii from other recognized Brachyspira species. Although discriminated genotypically, the three genetic groups are phenotypically similar. By electron microscopy, cells of different strains of B. hampsonii measure 5 to 10 μm by 0.28 to 0.34 μm, with one or two flat curves, and have 10 to 14 periplasmic flagella inserted at each cell end. Using a comprehensive evaluation of genotypic (gene comparisons and multilocus sequence typing and analysis), genomic (dDDH, ANI, and AAI) and phenotypic (hemolysis, biochemical profiles, protein spectra, antibiogram, and pathogenicity) properties, we classify Brachyspira hampsonii sp. nov. as a unique species with genetically diverse yet phenotypically similar genomovars (I, II, and III). We designate the type strain NSH-16 (= ATCC BAA-2463 = NCTC 13792).

Cross-reactions in specific Brachyspira spp. PCR assays caused by "Brachyspira hampsonii" isolates: implications for detection

An emerging novel spirochete in swine, provisionally designated "Brachyspira hampsonii," has been detected worldwide. It has been associated with swine dysentery and cannot be differentiated from B. hyodysenteriae, the classical etiologic agent of this disease, using standard phenotypic methods. We evaluated cross-reactions of "B. hampsonii" isolates recovered from avian species in some of the currently available species-specific polymerase chain reaction (PCR) assays for the identification of swine Brachyspira species. Ten avian "B. hampsonii" isolates recovered from wild waterfowl were used. No false-positive results were recorded with a B. pilosicoli-specific PCR based on the amplification of a fragment of the 16S rRNA gene. However, the percentage of false-positive results varied, with a range of 10-80%, in the evaluated B. hyodysenteriae-specific assays based on the amplification of the 23S rRNA, nox, and tlyA genes. Similarly, results of the B. intermedia-specific PCR assays yielded poor specificity, with up to 80% of the "B. hampsonii" isolates tested giving false-positive results. Finally, 2 "B. hampsonii" avian isolates yielded a positive result in a B. innocens- and B. murdochii-specific PCR. This result should be interpreted very cautiously as these 2 isolates could represent a recombinant genotype.

Comparison of Brachyspira hyodysenteriae Isolates Recovered from Pigs in Apparently Healthy Multiplier Herds with Isolates from Herds with Swine Dysentery

Swine dysentery (SD) is a mucohaemorrhagic colitis of grower/finisher pigs classically resulting from infection by the anaerobic intestinal spirochaete Brachyspira hyodysenteriae. This study aimed to determine whether B. hyodysenteriae isolates from pigs in three healthy German multiplier herds supplying gilts to other farms differed from isolates from nine German production herds with SD. Isolates were subjected to whole genomic sequencing, and in silico multilocus sequence typing showed that those from the three multiplier herds were of previously undescribed sequence types (ST132, ST133 and ST134), with all isolates from the same herd having the same ST. All isolates were examined for the presence of 332 genes encoding predicted virulence or virulence lifestyle associated factors, and these were well conserved. Isolates from one multiplier herd were atypical in being weakly haemolytic: they had 10 amino acid substitutions in the haemolysin III protein and five in the haemolysin activation protein compared to reference strain WA1, and had a disruption in the promoter site of the hlyA gene. These changes likely contribute to the weakly haemolytic phenotype and putative lack of virulence. These same isolates also had nine base pair insertions in the iron metabolism genes bitB and bitC and lacked five of six plasmid genes that previously have been associated with colonisation. Other overall differences between isolates from the different herds were in genes from three of five outer membrane proteins, which were not found in all the isolates, and in members of a block of six plasmid genes. Isolates from three herds with SD had all six plasmid genes, while isolates lacking some of these genes were found in the three healthy herds-but also in isolates from six herds with SD. Other differences in genes of unknown function or in gene expression may contribute to variation in virulence; alternatively, superior husbandry and better general health may have made pigs in the two multiplier herds colonised by "typical" strongly haemolytic isolates less susceptible to disease expression.

Swine Dysentery

Swine dysentery is a severe enteric disease in pigs, which is characterized by bloody to mucoid diarrhea and associated with reduced growth performance and variable mortality. This disease is most often observed in grower–finisher pigs, wherein susceptible pigs develop a significant mucohemorrhagic typhlocolitis following infection with strongly hemolytic spirochetes of the genus Brachyspira. While swine dysentery is endemic in many parts of the world, the disease had essentially disappeared in much of the United States by the mid-1990s as a result of industry consolidation and effective treatment, control, and elimination methods. However, since 2007, there has been a reported increase in laboratory diagnosis of swine dysentery in parts of North America along with the detection of novel pathogenic Brachyspira spp worldwide. Accordingly, there has been a renewed interest in swine dysentery and Brachyspira spp infections in pigs, particularly in areas where the disease was previously eliminated. This review provides an overview of knowledge on the etiology, pathogenesis, and diagnosis of swine dysentery, with insights into risk factors and control.

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.

Drug-susceptibility of isolates of Brachyspira hyodysenteriae isolated from colonic mucosal specimens of pigs collected from slaughter houses in Japan in 2009

Twenty nine isolates identified as Brachyspira hyodysenteriae were most susceptible to carbadox and metronidazole, whereas they were resistant to macrolides. The isolates showed intermediate susceptibility to tiamulin, lincomycin, penicillin G, ampicillin, chloramphenicol, tetracycline, enrofloxacin and valnemulin, with MIC₅₀ values ranging from 0.39 to 3.13.

Intestinal spirochaetes (genus Brachyspira) colonise wild birds in the southern Atlantic region and Antarctica

Introduction

The genus Brachyspira contains well-known enteric pathogens of veterinary significance, suggested agents of colonic disease in humans, and one potentially zoonotic agent. There are recent studies showing that Brachyspira are more widespread in the wildlife community than previously thought. There are no records of this genus in wildlife from the southern Atlantic region and Antarctica. Our aim was therefore, to determine whether intestinal spirochaetes of genus Brachyspira colonise marine and coastal birds in this region.

Method

Faecal samples were collected from marine and coastal birds in the southern Atlantic region, including sub-Antarctic islands and Antarctica, in 2002, 2009, and 2012, with the aim to isolate and characterise zoonotic agents. In total, 205 samples from 11 bird species were selectively cultured for intestinal spirochaetes of genus Brachyspira. To identify isolates to species level, they were subjected to phenotyping, species-specific polymerase chain reactions, sequencing of partial 16S rRNA, NADH oxidase (nox), and tlyA genes, and phylogenetic analysis. Antimicrobial susceptibility tests were performed.

Results

Fourteen unique strains were obtained from 10 birds of three species: four snowy sheathbills (Chionis albus), three kelp geese (Chloephaga hybrida subsp. malvinarum), and three brown skua (Stercorarius antarcticus subsp. lonnbergi) sampled on the Falkland Islands, Tierra del Fuego in Argentina, South Georgia, South Shetland Islands, and the Antarctic Peninsula. Five Brachyspira strains were closely related to potentially enteropathogenic Brachyspira sp. of chickens: B. intermedia (n=2, from snowy sheathbills), and B. alvinipulli (n=3, from a kelp goose and two snowy sheathbills). Three strains from kelp geese were most similar to the presumed non-pathogenic species ‘B. pulli’ and B. murdochii, whereas the remaining six strains could not be attributed to currently known species. No isolates related to human strains were found. None of the tested strains showed decreased susceptibility to tiamulin, valnemulin, doxycycline, tylvalosin, lincomycin, or tylosin.

Conclusions

This is the first report of intestinal spirochaetes from this region. Despite limitations of current diagnostic methods, our results, together with earlier studies, show that Brachyspira spp., including potentially pathogenic strains, occur globally among free-living avian hosts, and that this genus encompasses a higher degree of biodiversity than previously recognised.

Emergence of Brachyspira species and strains: reinforcing the need for surveillance

This short review discusses the increasing complexity that has developed around the understanding of Brachyspira species that infect pigs, and their ability to cause disease. It describes the recognition of new weakly haemolytic Brachyspira species, and the growing appreciation that Brachyspira pilosicoli and some other weakly haemolytic species may be pathogenic in pigs. It discusses swine dysentery (SD) caused by the strongly haemolytic Brachyspira hyodysenteriae, particularly the cyclical nature of the disease whereby it can largely disappear as a clinical problem from a farm or region, and re-emerge years later. The review then describes the recent emergence of two newly described strongly haemolytic pathogenic species, “Brachyspira suanatina” and “Brachyspira hampsonii” both of which appear to have reservoirs in migratory waterbirds, and which may be transmitted to and between pigs. “B. suanatina” seems to be confined to Scandinavia, whereas “B. hampsonii” has been reported in North America and Europe, causes a disease indistinguishable from SD, and has required the development of new routine diagnostic tests. Besides the emergence of new species, strains of known Brachyspira species have emerged that vary in important biological properties, including antimicrobial susceptibility and virulence. Strains can be tracked locally and at the national and international levels by identifying them using multilocus sequence typing (MLST) and comparing them against sequence data for strains in the PubMLST databases. Using MLST in conjunction with data on antimicrobial susceptibility can form the basis for surveillance programs to track the movement of resistant clones. In addition some strains of B. hyodysenteriae have low virulence potential, and some of these have been found to lack the B. hyodysenteriae 36 kB plasmid or certain genes on the plasmid whose activity may be associated with colonization. Lack of the plasmid or the genes can be identified using PCR testing, and this information can be added to the MLST and resistance data to undertake detailed surveillance. Strains of low virulence are particularly important where they occur in high health status breeding herds without causing obvious disease: potentially they could be transmitted to production herds where they may colonize more effectively and cause disease under stressful commercial conditions.

Anaerobic spirochaetes and animals

Anaerobic spirochaetes colonise the large intestine of many avian and mammalian host species. The most well known pathogenic species is the strongly haemolytic Brachyspira hyodysenteriae that was first isolated from pigs with swine dysentery (SD) in the early 1970s. Classical SD is a severe mucohaemorrhagic colitis that occurs in growing pigs and is endemic in most pig-rearing areas of the world. The spirochaete acts in concert with other components of the colonic microbiota to disrupt the integrity of the colonic epithelium and induce inflammation. In recent years two new strongly haemolytic species, the proposed ‘Brachyspira suanatina' and ‘Brachyspira hampsonii', both with reservoirs in migratory water birds, have been described as new and emerging agents of SD in the northern hemisphere. Weakly haemolytic species also have been described, some of which have pathogenic potential. In particular Brachyspira pilosicoli causes a mild colitis and diarrhoea in many species, including human beings, whilst Brachyspira intermedia is a common pathogen in adult poultry. Infection with B. intermedia and/or B. pilosicoli can cause wet litter, faecal staining of eggshells and delays in reaching peak egg production. Options for control of these widespread and economically significant anaerobic infections are limited.

Understanding the molecular epidemiology and global relationships of Brachyspira hyodysenteriae from swine herds in the United States: a multi-locus sequence typing approach

Outbreaks of mucohemorrhagic diarrhea in pigs caused by Brachyspira hyodysenteriae in the late 2000s indicated the re-emergence of Swine Dysentery (SD) in the U.S. Although the clinical disease was absent in the U.S. since the early 1990s, it continued to cause significant economic losses to other swine rearing countries worldwide. This study aims to fill the gap in knowledge pertaining to the re-emergence and epidemiology of B. hyodysenteriae in the U.S. and its global relationships using a multi-locus sequence typing (MLST) approach. Fifty-nine post re-emergent isolates originating from a variety of sources in the U.S. were characterized by MLST, analyzed for epidemiological relationships (within and between multiple sites of swine systems), and were compared with pre re-emergent isolates from the U.S. Information for an additional 272 global isolates from the MLST database was utilized for international comparisons. Thirteen nucleotide sequence types (STs) including a predominant genotype (ST93) were identified in the post re-emergent U.S. isolates; some of which showed genetic similarity to the pre re-emergent STs thereby suggesting its likely role in the re-emergence of SD. In the U.S., in general, no more than one ST was found on a site; multiple sites of a common system shared a ST; and STs found in the U.S. were distinct from those identified globally. Of the 110 STs characterized from ten countries, only two were found in more than one country. The U.S. and global populations, identified as clonal and heterogeneous based on STs, showed close relatedness based on amino acid types (AATs). One predicted founder type (AAT9) and multiple predicted subgroup founder types identified for both the U.S. and the global population indicate the potential microevolution of this pathogen. This study elucidates the strain diversity and microevolution of B. hyodysenteriae, and highlights the utility of MLST for epidemiological and surveillance studies.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry for rapid identification of Brachyspira species isolated from swine, including the newly described “Brachyspira hampsonii”

The Brachyspira species traditionally associated with swine dysentery and other diarrheal diseases in pigs are Brachyspira hyodysenteriae, Brachyspira pilosicoli, and, to a lesser extent, Brachyspira murdochii. “ Brachyspira hampsonii” is a recently proposed novel species that causes clinical disease similar to that caused by B. hyodysenteriae. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems are increasingly available in veterinary diagnostic laboratories, are less expensive, and are faster than traditional microbiological and molecular methods for identification. Thirty-three isolates associated with Brachyspira species of importance to swine were added to an existing MALDI-TOF MS database library. In total, species included in the library were: B. hyodysenteriae, “ B. hampsonii” clades I and II, Brachyspira innocens, Brachyspira intermedia, B. murdochii, and B. pilosicoli. A comparison between MALDI-TOF MS and nox sequencing was completed on 176 field isolates. Of the 176 field isolates, 174 (98.9%) matched species identification by both methods. Thirty field isolates were identified by both methods as “ B. hampsonii”. Twenty-seven of the 30 (90%) “ B. hampsonii” field isolates matched clade designation in both assays. The nox sequencing identified 26 as “ B. hampsonii” clade I and 4 as clade II. Comparatively, MALDI-TOF MS identified 25 of the 30 as “ B. hampsonii” clade I and 5 as clade II. The current study indicates MALDI-TOF MS is a reliable tool for the identification of swine Brachyspira species; however, final clade designation for “ B. hampsonii” may still require molecular techniques.

Identification of weakly haemolytic Brachyspira isolates recovered from pigs with diarrhoea in Spain and Portugal and comparison with results from other countries

Weakly haemolytic anaerobic intestinal spirochaetes of the genus Brachyspira are commonly identified based on species-specific gene sequences. Apart from the pathogenic Brachyspira pilosicoli, the distribution and disease associations of the other weakly haemolytic Brachyspira species in pigs have not been comprehensively investigated. In this study weakly haemolytic Brachyspira isolates (n=67) from Spanish and Portuguese pigs with diarrhoea, negative in a routine diagnostic PCR for B. pilosicoli, were identified by sequencing their NADH oxidase genes (nox). Nearly half the isolates were identified as Brachyspira murdochii (n=31; 46.3%). The others were Brachyspira innocens (n=26; 38.8%), Brachyspira intermedia (n=7; 10.4%), "Brachyspira pulli" (n=1; 1.5%) and a potentially novel Brachyspira species (n=2; 3%). Multilocus sequence typing (MLST) on a subset of 18 isolates confirmed their species designations, including the potential new species, and identified similarities to strains from other countries.

Fluorescent in situ hybridization for detection of "Brachyspira hampsonii" in porcine colonic tissues

Swine dysentery is classically associated with infection by the strongly beta-hemolytic Brachyspira hyodysenteriae; however, the proposed novel species "Brachyspira hampsonii" has also been isolated from clinical cases of dysentery in the United States and Canada. Microbial culture is highly sensitive for detecting Brachyspira in clinical samples but requires several days for completion and is often followed by molecular testing for speciation. Alternatively, in situ hybridization using molecular probes applied to sections of formalin-fixed tissue can provide rapid, culture-independent identification of agents observed histologically. Accordingly, a fluorescent in situ hybridization assay was developed for confirmation of a clinical diagnosis of swine dysentery associated with infection by "B. hampsonii." An oligonucleotide probe (Hamp1210) targeting a specific 23S ribosomal RNA sequence of "B. hampsonii" was developed following sequence analysis and comparison of numerous Brachyspira spp. clinical isolates with reference sequences available in GenBank. The application of Hamp1210 and a previously published probe for B. hyodysenteriae (Hyo1210) to diseased colonic tissues successfully detected the target species in both experimentally infected pigs and naturally infected pigs from field cases, and the Hamp1210 probe consistently detected both clade I and clade II isolates of "B. hampsonii"; however, a strong positive signal was also observed in a single case where the Hamp1210 probe was applied to tissues infected with Brachyspira intermedia. In situ hybridization incorporating the Hamp1210 probe can reduce the delay from sample submission to pathogen identification in cases of swine dysentery associated with "B. hampsonii" infection where formalin-fixed tissues are available.

Reproduction of mucohaemorrhagic diarrhea and colitis indistinguishable from swine dysentery following experimental inoculation with "Brachyspira hampsonii" strain 30446

Background

Mucohaemorrhagic diarrhea caused by Brachyspira hyodysenteriae, swine dysentery, is a severe production limiting disease of swine. Recently, pigs in western Canada with clinical signs indistinguishable from swine dysentery were observed. Despite the presence of spirochetes on fecal smears, recognized Brachyspira spp. including B. hyodysenteriae could not be identified. A phylogenetically distinct Brachyspira, called “B. hampsonii” strain 30446, however was isolated. The purpose of this study was to experimentally reproduce mucohaemorrhagic colitis and characterize strain 30446 shedding following inoculation.

Methods and Findings

Eighteen 13-week-old pigs were randomly assigned to inoculation (n = 12) or control (n = 6) groups in each of two trials. In trial 1, pigs were inoculated with a tissue homogenate collected from clinically affected field cases. In trial 2, pigs were inoculated with a pure broth culture of strain 30446. In both trials, mucohaemorrhagic diarrhea was significantly more common in inoculated pigs than controls, all of which remained healthy. In animals with mucohaemorrhagic diarrhea, significantly more spirochetes were observed on Gram stained fecal smears, and higher numbers of strain 30446 genome equivalents were detected by quantitative PCR (qPCR). Strain 30446 was cultured from colon and/or feces of all affected but no control animals at necropsy.

Conclusions

“Brachyspira hampsonii” strain 30446 causes mucohaemorrhagic diarrhea in pigs following a 4–9 day incubation period. Fecal shedding was detectable by day 4 post inoculation, and rarely preceded the onset of mucoid or haemorrhagic diarrhea by more than 2 days. Culture and 30446-specific qPCR are reliable methods of detection of this organism in feces and tissues of diarrheic pigs. The emergence of a novel Brachyspira spp., such as “B. hampsonii”, creates diagnostic challenges including higher risk of false negative diagnostic tests. We therefore recommend diagnostic laboratories routinely use Brachyspira culture, nox-based and species-specific PCR, and DNA sequencing to diagnose Brachyspira-associated colitis in pigs.

Phenotypic and molecular characterization of a novel strongly hemolytic Brachyspira species, provisionally designated "Brachyspira hampsonii"

Since 2007, outbreaks of severe bloody diarrhea and hemorrhagic colitis have been reported in the United States and Canada. Though the primary causative agent of swine dysentery is Brachyspira hyodysenteriae, which is strongly hemolytic, the current report describes the isolation of a novel strongly hemolytic Brachyspira sp. This novel Brachyspira sp. was identified from clinical submissions at the Minnesota Veterinary Diagnostic Laboratory, and 40 of such isolates were obtained from 22 clinical submissions representing 5 states. Isolates were confirmed to be different from any known Brachyspira sp. on the basis of phylogenetic analysis of nucleotide sequences of nox and 16S ribosomal RNA (rRNA) genes. Phylogenetic analyses grouped all isolates into 2 clades (clades I and II), and grouping patterns were similar for both nox and 16S rRNA gene sequence analyses. Phenotypically, all isolates were indole and hippurate negative, and enzymatic profiling indicated 2 types of profiles, irrespective of the phylogenetic grouping, differing only in the production of β-glucosidase. The results suggest that a potentially virulent new species of Brachyspira sp., provisionally named "Brachyspira hampsonii ", is circulating among swine herds in the United States.

Development of a real-time PCR for identification of brachyspira species in human colonic biopsies

BACKGROUND

Brachyspira species are fastidious anaerobic microorganisms, that infect the colon of various animals. The genus contains both important pathogens of livestock as well as commensals. Two species are known to infect humans: B. aalborgi and B. pilosicoli. There is some evidence suggesting that the veterinary pathogenic B. pilosicoli is a potential zoonotic agent, however, since diagnosis in humans is based on histopathology of colon biopsies, species identification is not routinely performed in human materials.

METHODS

The study population comprised 57 patients with microscopic evidence of Brachyspira infection and 26 patients with no histopathological evidence of Brachyspira infection. Concomitant faecal samples were available from three infected patients. Based on publically available 16S rDNA gene sequences of all Brachyspira species, species-specific primer sets were designed. DNA was extracted and tested by real-time PCR and 16S rDNA was sequenced.

RESULTS

Sensitivity and specificity for identification of Brachyspira species in colon biopsies was 100% and 87.7% respectively. Sequencing revealed B. pilosicoli in 15.4% of patients, B. aalborgi in 76.9% and a third species, tentatively named "Brachyspira hominis", in 26.2%. Ten patients (12.3%) had a double and two (3.1%) a triple infection. The presence of Brachyspira pilosicoli was significantly associated with inflammatory changes in the colon-biopsy (p=0.028).

CONCLUSIONS

This newly designed PCR allows for sub-differentiation of Brachyspira species in patient material and thus allows large-scaled surveillance studies to elucidate the pathogenicity of human Brachyspira infections. One-third of affected patients appeared to be infected with a novel species.

MALDI-TOF MS analysis of human and animal Brachyspira species and benefits of database extension

Spirochaetes belonging to the genus Brachyspira are anaerobic bacteria that colonize the large intestine of humans and animals, mainly pigs. The main species are namely, B. hyodysenteriae, the etiological agent of swine dysentery, B. pilosicoli, a zoonotic agent causing colonic spirochaetosis both in humans and different animal species, B. aalborgi, exclusively infecting humans causing colonic spirochaetosis, B. intermedia, a potential animal pathogen, B. innocens and B. murdochii, generally commensal of pigs, and B. alvinipulli, found in egg laying hens with diarrhea. In this study, for the first time, MALDI-TOF MS was applied on Brachyspira strains of human and animal origins, supplementing the existing database, limited to the species B. murdochii only, with spirochaetal protein profiles and demonstrating its usefulness in the rapid, cheap and reliable identification of Brachyspira strains at the species level, overcoming the problems previously encountered in the identification of these spirochaetes when using biochemical and genetic-based methods. Moreover, a dendrogram based on protein profiles of the different spirochaetal species was generated reflecting their host spectrum, showing in the same branch the only two species able to infect humans (B. aalborgi and B. pilosicoli) and in the other branch the spirochaetes infecting exclusively animals.

Comparative virulence of clinical Brachyspira spp. isolates in inoculated pigs

Classical swine dysentery is associated with the presence of the strongly beta-hemolytic Brachyspira hyodysenteriae. However, multiple Brachyspira spp. can colonize the porcine colon. Since 2008, several Brachyspira spp. not identified as B. hyodysenteriae by genotypic and/or phenotypic methods have been isolated from the feces of pigs with clinical disease typical of swine dysentery. In the current study, 8 clinical isolates, including 5 strongly beta-hemolytic and 3 weakly beta-hemolytic Brachyspira strains, and a reference strain of B. hyodysenteriae (B204) were inoculated into pigs (n = 6 per isolate) to compare pathogenic potential following oral inoculation. Results revealed that strongly beta-hemolytic isolates induced significantly greater typhlocolitis than those that are weakly beta-hemolytic, regardless of the genetic identification of the isolate, and that strongly beta-hemolytic isolates identified as "Brachyspira sp. SASK30446" and Brachyspira intermedia by polymerase chain reaction (PCR) produced lesions similar to those caused by B. hyodysenteriae. The results suggest that phenotypic culture characteristics of Brachyspira spp. may be a more sensitive indicator of potential to induce dysentery-like disease in pigs than molecular identification alone based on currently available PCR assays. Additionally, culture of mucosal scrapings obtained at necropsy was more sensitive than direct PCR on the same samples for detection of Brachyspira spp.

An up-date on the differentiation of Brachyspira species from pigs with nox-PCR-based restriction fragment length polymorphism

Different Brachyspira (B.) species colonize the porcine intestinal tract, some of which are pathogens of significant clinical and economic importance. In 2002 we published a novel molecular method for differentiation of Brachyspira species from pigs based on the amplification of the nox-gene and the generation of species-specific restriction patterns (nox-RFLP) using the enzymes BfmI and DpnII (Rohde et al., 2002). We applied this method for identification in addition to biochemical testing in doubtful cases until 2008. Since 2009 we have used it as the first line method of identification. The current study documents the results of examining 2050 Brachyspira isolates collected from January 2009 to December 2011. In addition to identifying isolates with previously described patterns, four novel restriction fragment length patterns were observed, and isolates with these patterns could be assigned to the species B. intermedia and the B. innocens/murdochii complex on the basis of their phenotypic properties and by nox-sequence analysis. In 2007 a potentially new Brachyspira species, "B. suanatina", was described in Swedish pigs (Råsbäck et al., 2007). From the published nox-gene sequence it could be expected that this Brachypira species should show a new restriction pattern making nox-RFLP a suitable technique for identification of "B. suanatina". In this study the new restriction fragment length pattern could be demonstrated in one of the strains described by Råsbäck et al. (AN4859/03). Nevertheless, no isolates with this new pattern corresponding to "B. suanatina" were identified amongst the 2050 Brachyspira isolates examined from northern Germany.

Demonstration of genes encoding virulence and virulence life-style factors in Brachyspira spp. isolates from pigs

The distribution of many genes encoding virulence and virulence life-style (VL-S) factors in Brachyspira (B.) hyodysenteriae and other Brachyspira species are largely unknown. Their knowledge is essential e.g. for the improvement of diagnostic methods targeting the detection and differentiation of the species. Thus 121 German Brachyspira field isolates from diarrhoeic pigs were characterized down to the species level by restriction fragment length polymorphism analysis of the nox gene and subsequently subjected to polymerase chain reaction detecting VL-S genes for inner (clpX) and outer membrane proteins (OMPs: bhlp16, bhlp17.6, bhlp29.7, bhmp39f, bhmp39h), hemolysins (hlyA/ACP, tlyA), iron metabolism (ftnA, bitC), and aerotolerance (nox). For comparison, B. hyodysenteriae reference strains from the USA (n=7) and Australia (2) were used. Of all genes tested only nox was detected in all isolates. The simultaneous presence of both the tlyA and hlyA/ACP was restricted to the species B. hyodysenteriae. The hlyA infrequently occurred also in weakly hemolytic Brachyspira. Similarly to tlyA and hlyA all B. hyodysenteriae strains contained the ferritin gene ftnA which was also found in two Brachyspira intermedia isolates. OMP encoding genes were present in B. hyodysenteriae field isolates in rates of 0% (bhlp17.6, bhmp39h), 58.1% (bhlp29.7), and 97.3% (bhmp39f). Since the study revealed a high genetic heterogeneity among German B. hyodysenteriae field isolates differentiating them from USA as well as Australian strains, targets for diagnostic PCR were limited to the nox gene (genus specific PCR) as well as to the species specific nox(hyo) gene and the combination of hlyA and tlyA which allow to specifically detect B. hyodysenteriae.

Phenotypic and molecular characterization of Brachyspira spp. isolated from wild rodents

The occurrence of intestinal spirochaetes of genus Brachyspira in wild rodents was studied by cultivating 209 caecal samples. Spirochaetal cultures were obtained from 83% of rats and 33% of house mice. Biochemical characterization and six different species-specific PCR methods were applied to 101 of 118 isolates and a selection of 34 brachyspiras were further studied by sequencing of the 16S rRNA gene. The results showed that isolates representing all the established biochemical phenotypes could be cultured from the rodents, including the porcine pathogens Brachyspira hyodysenteriae and Brachyspira pilosicoli. Phylogenetic studies indicated that rodents carry Brachyspira spp. that are closely related to porcine and avian isolates, as well as variants previously not described. One group of hippurate-negative rat isolates were shown to possess the 16S rRNA gene hexa(T) nucleotide segment, previously described only in B. pilosicoli and 'Brachyspira corvi', and phylogenetically they formed a sister lineage of the B. pilosicoli cluster. Furthermore, a large number of the rodents were colonized by slowly growing, non- or weakly haemolytic spirochaetes. Most of these brachyspiras were isolated at 37°C and phylogenetically they formed two separate clusters. Sequence analysis of their 16S rRNA genes indicated that the new variants of Brachyspira spp. may constitute novel species of the genus Brachyspira.

Prevalence, disease associations and risk factors for colonization with intestinal spirochaetes (Brachyspira spp.) in flocks of laying hens in north-eastern Italy

The present study investigated the occurrence of anaerobic intestinal spirochaetes of the genus Brachyspira in laying hen flocks in Treviso province, north-eastern Italy, with respect to prevalence, spirochaete species present, disease associations and risk factors for colonization. A total of 450 faecal samples from 45 sheds on 29 laying hen farms were cultured for intestinal spirochaetes. Nineteen sheds on 12 farms contained chickens with symptoms consistent with avian intestinal spirochaetosis, including reduced egg production, wet litter and/or pasty vents. Spirochaetes were isolated from 157 (34.8%) samples from 21 (72.4%) farms, and from 32 (71.1%) sheds. From these positive samples, 189 spirochaetal isolates were speciated using three polymerase chain reaction assays and a restriction fragment polymorphism analysis of 16S rDNA polymerase chain reaction products. Overall, 52 (27.5%) isolates were identified as pathogenic Brachyspira intermedia, 26 (13.8%) as pathogenic Brachyspira pilosicoli, 93 (49.7%) as non-pathogenic (Brachyspira innocens/Brachyspira murdochii), and 18 (9.6%) were unidentified. Faeces from 14 sheds (31%) on 10 farms (34.5%) contained B. intermedia and/or B. pilosicoli, and disease consistent with avian intestinal spirochaetosis was observed in nine of these sheds on seven farms. There was a significant association (P=0.042) between the presence of spirochaetes and using deep pits rather than conveyor belts for manure disposal. Sheds housing chickens >40 weeks of age were significantly more likely to contain spirochaetes (P=0.048) and pathogenic species (P=007) than sheds housing younger chickens. A significant association (P=0.02) was found between infection with pathogenic spirochaetes and reduced egg production.

Intestinal spirochetes isolated from wild-living jackdaws, hooded crows and rooks (genus Corvus): provisionally designated "Brachyspira corvi" sp. nov

Intestinal spirochetes of genus Brachyspira are commonly isolated from mammalian and avian hosts, and several species have been reported to cause enteric disease in pigs and birds. Except for a previous publication on three isolates from corvid birds (order Passeriformes, family Corvidae, genus Corvus), of which two are further studied in this paper, no other reports exist on Brachyspira spp. of passerine birds. In this study, cloacal and intestinal swabs of small and large intestines were collected from 116 corvid birds of three species, i.e. jackdaws (Corvus monedula), hooded crows (Corvus corone cornix) and rooks (Corvus frugilegus), from four separate geographical locations in Sweden. Isolates were obtained by selective culture from 43 of 116 birds. All isolates were weakly hemolytic, indole-negative and lacked hippurate cleavage capacity. Examination by light microscopy did not indicate association with enteric disease in necropsied birds. Pure spirochete cultures were obtained by serial dilution and subculture, and selected isolates were analyzed by PCR (n=14), randomly amplified polymorphic DNA (RAPD) (n=14), and sequencing of the almost complete 16S rRNA (n=14), and partial nox genes (n=4). Positive reactions were noticed by PCR targeting a hexa-T segment of the 16S rRNA gene, which has been previously reported as a signature characteristic of Brachyspira pilosicoli. By 16S rRNA gene sequencing, the isolates formed a separate cluster related to genus Brachyspira, but not consistent with any presently recognized or proposed Brachyspira sp. The sequence similarity of the 16S rRNA gene among the isolates from corvid birds was 99.7-100%. Compared to 16S rRNA gene sequence data from all presently recognized and several proposed Brachyspira spp. the sequence similarity of the isolates from corvid birds varied between 94.1 and 96.5%. In a radial tree based on nox gene sequences, all four analyzed isolates from corvid birds formed a separate cluster. By RAPD analysis, the banding patterns of the isolates differed from all type strains of Brachyspira spp. Based on the results presented in this paper, we propose that the described isolates from corvid birds belong to a novel species within genus Brachyspira, with the provisional name "Brachyspira corvi" (cor'vi. L gen. n. corvi, of a crow).