Identification of Serpulina species associated with porcine colitis by biochemical analysis and PCR

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.

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.

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.

Prevalence and risk factors for Lawsonia intracellularis, Brachyspira hyodysenteriae and Salmonella spp. in finishing pigs in Polish farrow-to-finish swine herds

The aim of the study was to estimate the herd-level, within-herd prevalence, the frequency of mixed infections and risk factors for L. intracellularis, B. hyodysenteriae and Salmonella spp. in selected farrow-to-finish Polish pig herds. A total of 254 pooled fecal samples were collected from 9 to 24 week-old pigs in 70 herds. Real time PCR for detection of L. intracellularis and B. hyodysenteriae was performed. For Salmonella spp. bacteriological examination was performed. The herd-level prevalences of L. intracellularis, B. hyodysenteriae and Salmonella spp. among examined herds were 65.7%, 1.4% and 8.6%, respectively. The within-herd prevalences (in positive herds) for L. intracellularis, B. hyodysenteriae and Salmonella spp. were 51.5%, 75.0% and 30.4%, respectively. All herds with diarrhea observed during sampling were infected with L. intracellularis and 60% of herds with no diarrhea at the moment of sampling were infected with L. intracellularis (p=0.035). In herds with more than 200 sows the prevalence of Salmonella spp. was significantly higher compared to herds with less than 200 sows (p=0.027). In herds where all-in/all-out (AIAO) was respected, prevalence of L. intracellularis was significantly lower than in herds where this rule was not kept (p=0.024). Obtained results confirm that L. intracellularis is the major cause of bacterial diarrhea in finishing pigs. The present study identified AIAO and herd size as a risk factor, at the herd level, for L. intracellularis and Salmonella spp., respectively.

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.

Brachyspira and its role in avian intestinal spirochaetosis

The fastidious, anaerobic spirochaete Brachyspira is capable of causing enteric disease in avian, porcine and human hosts, amongst others, with a potential for zoonotic transmission. Avian intestinal spirochaetosis (AIS), the resulting disease from colonisation of the caeca and colon of poultry by Brachyspira leads to production losses, with an estimated annual cost of circa £ 18 million to the commercial layer industry in the United Kingdom. Of seven known and several proposed species of Brachyspira, three are currently considered pathogenic to poultry; B. alvinipulli, B. intermedia and B. pilosicoli. Currently, AIS is primarily prevented by strict biosecurity controls and is treated using antimicrobials, including tiamulin. Other treatment strategies have been explored, including vaccination and probiotics, but such developments have been hindered by a limited understanding of the pathobiology of Brachyspira. A lack of knowledge of the metabolic capabilities and little genomic information for Brachyspira has resulted in a limited understanding of the pathobiology. In addition to an emergence of antibiotic resistance amongst Brachyspira, bans on the prophylactic use of antimicrobials in livestock are driving an urgent requirement for alternative treatment strategies for Brachyspira-related diseases, such as AIS. Advances in the molecular biology and genomics of Brachyspira heralds the potential for the development of tools for genetic manipulation to gain an improved understanding of the pathogenesis of Brachyspira.

Oral treatment of chickens with Lactobacillus reuteri LM1 reduces Brachyspira pilosicoli-induced pathology

Avian intestinal spirochaetosis (AIS) results from the colonization of the caeca and colon of poultry by pathogenic Brachyspira, notably Brachyspira pilosicoli. Following the ban on the use of antibiotic growth promoters in the European Union in 2006, the number of cases of AIS has increased, which, alongside emerging antimicrobial resistance in Brachyspira, has driven renewed interest in alternative intervention strategies. Lactobacillus-based probiotics have been shown to protect against infection with common enteric pathogens in livestock. Our previous studies have shown that Lactobacillus reuteri LM1 antagonizes aspects of the pathobiology of Brachyspira in vitro. Here, we showed that L. reuteri LM1 mitigates the clinical symptoms of AIS in chickens experimentally challenged with B. pilosicoli. Two groups of 15 commercial laying hens were challenged experimentally by oral gavage with B. pilosicoli B2904 at 18 weeks of age; one group received unsupplemented drinking water and the other received L. reuteri LM1 in drinking water from 1 week prior to challenge with Brachyspira and thereafter for the duration of the study. This treatment regime was protective. Specifically, B. pilosicoli was detected by culture in fewer birds, bird weights were higher, faecal moisture contents were significantly lower (P<0.05) and egg production as assessed by egg weight and faecal staining score was improved (P<0.05). Also, at post-mortem examination, significantly fewer B. pilosicoli were recovered from treated birds (P<0.05), with only mild-moderate histopathological changes observed. These data suggest that L. reuteri LM1 may be a useful tool in the control of AIS.

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 genomics of Brachyspira pilosicoli strains: genome rearrangements, reductions and correlation of genetic compliment with phenotypic diversity

Background

The anaerobic spirochaete Brachyspira pilosicoli causes enteric disease in avian, porcine and human hosts, amongst others. To date, the only available genome sequence of B. pilosicoli is that of strain 95/1000, a porcine isolate. In the first intra-species genome comparison within the Brachyspira genus, we report the whole genome sequence of B. pilosicoli B2904, an avian isolate, the incomplete genome sequence of B. pilosicoli WesB, a human isolate, and the comparisons with B. pilosicoli 95/1000. We also draw on incomplete genome sequences from three other Brachyspira species. Finally we report the first application of the high-throughput Biolog phenotype screening tool on the B. pilosicoli strains for detailed comparisons between genotype and phenotype.

Results

Feature and sequence genome comparisons revealed a high degree of similarity between the three B. pilosicoli strains, although the genomes of B2904 and WesB were larger than that of 95/1000 (~2,765, 2.890 and 2.596 Mb, respectively). Genome rearrangements were observed which correlated largely with the positions of mobile genetic elements. Through comparison of the B2904 and WesB genomes with the 95/1000 genome, features that we propose are non-essential due to their absence from 95/1000 include a peptidase, glycine reductase complex components and transposases. Novel bacteriophages were detected in the newly-sequenced genomes, which appeared to have involvement in intra- and inter-species horizontal gene transfer. Phenotypic differences predicted from genome analysis, such as the lack of genes for glucuronate catabolism in 95/1000, were confirmed by phenotyping.

Conclusions

The availability of multiple B. pilosicoli genome sequences has allowed us to demonstrate the substantial genomic variation that exists between these strains, and provides an insight into genetic events that are shaping the species. In addition, phenotype screening allowed determination of how genotypic differences translated to phenotype. Further application of such comparisons will improve understanding of the metabolic capabilities of Brachyspira species.

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.

Faecal excretion of intestinal spirochaetes by urban dogs, and their pathogenicity in a chick model of intestinal spirochaetosis

This study aimed to obtain information about the types of spirochaetes colonising urban dogs in Thailand, and to investigate their pathogenic potential in a day-old chick model of intestinal spirochaetosis. Spirochaetes were isolated from the faeces of six of 47 (12.8%) healthy dogs and 11 of 104 (10.6%) dogs with diarrhoea. Their biochemical properties and 16S ribosomal DNA sequences were analysed. Four isolates were identified as Brachyspira pilosicoli, three resembled "Brachyspira pulli", nine clustered with "Brachyspira canis" and one was similar to Brachyspira intermedia. Canine isolates of B. pilosicoli, "B. canis" and "B. pulli", and control strains of Brachyspira hyodysenteriae, B. pilosicoli and Brachyspira innocens colonised experimentally infected day-old chicks. The chicks did not develop diarrhoea, but were significantly lighter than the non-infected group and those infected with B. innocens after 21 days (P<0.05). Using immunohistochemistry, spirochaetes were observed covering the surface epithelium and in the crypts of chicks in all three groups challenged with the canine isolates. Variable histopathological changes were seen, with the greatest inflammatory cell infiltration into the lamina propria occurring in the group infected with "B. pulli". Canine "B. canis", "B. pulli" and B. pilosicoli isolates may have pathogenic potential.

Rapid and accurate diagnosis of human intestinal spirochetosis by fluorescence in situ hybridization

Human intestinal spirochetosis (HIS) is associated with overgrowth of the large intestine by spirochetes of the genus Brachyspira. The microbiological diagnosis of HIS is hampered by the fastidious nature and slow growth of Brachyspira spp. In clinical practice, HIS is diagnosed histopathologically, and a significant portion of cases may be missed. Fluorescence in situ hybridization (FISH) is a molecular method that allows the visualization and identification of single bacteria within tissue sections. In this study, we analyzed intestinal biopsy samples from five patients with possible HIS. All specimens yielded positive results by histopathological techniques. PCR amplification and sequencing of the 16S rRNA gene were performed. Sequences of two isolates clustered in the group of Brachyspira aalborgi, whereas in three cases, the sequences were highly similar to that of Brachyspira pilosicoli. Three phylotypes showed mismatches at distinct nucleotide positions with Brachyspira sp. sequences published previously. In addition, culture for Brachyspira was successful in three cases. On the basis of these data, we designed and evaluated a Brachyspira genus-specific 16S rRNA-directed FISH probe that detects all of the Brachyspira spp. published to date. FISH of biopsy samples resulted in strong, unequivocal signals of brush-like formations at the crypt surfaces. This technique allowed simultaneous visualization of single spirochetes and their identification as Brachyspira spp. In conclusion, FISH provides a fast and accurate technique for the visualization and identification of intestinal spirochetes in tissue sections. It therefore represents a valuable tool for routine diagnosis of HIS.

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).

Comparative pathology and pathogenesis of naturally acquired and experimentally induced colonic spirochetosis

Research in the past decade has led to the recognition ofBrachyspira(formerlySerpulina)pilosicolias the primary etiologic agent of colonic spirochetosis (CS), an emerging cause of colitis in humans and animals. Attachment of spirochetes to the epithelial surface of the lower intestine is considered to be the hallmark of CS. However, becauseB. pilosicoli, B. aalborgiand unclassified flagellated bacteria are found singly or together in humans and non-human primates with CS lesions, attachment of spiral-shaped bacteria may not represent the same etiopathogenetic entity in all hosts. Moreover, North American opossums with CS are infected withB. aalborgi-like spirochetes together with flagellated bacteria, whereasB. pilosicoliis found alone in dogs, pigs, chickens and other species of birds with CS. Conversely, guinea-pigs with CS have unidentified spirochetes that may beB. pilosicoli or B. aalborgi.The pig model of CS suggests that attachment ofB. pilosicolito epithelial cells may be transient. By contrast, persistence ofB. pilosicoliin the cecal and colonic crypt lumina, chronic inflammation caused by spirochetal invasion into the subepithelial lamina propria and translocation to extraintestinal sites may be more important than previously thought. This review describes the lesions seen in naturally occurring and experimentally induced CS of animals, and it sets the stage for future research into the pathogenic mechanisms of infection and colitis caused byB. pilosicoli.

Eradication of endemicBrachyspira pilosicoliinfection from a farrowing herd: a case report

Brachyspira pilosicoliandB. innocenswere isolated repeatedly from a herd of 60 sows which mostly produced feeder pigs but also raised some fattening pigs. Postweaning diarrhea had been a severe problem in this herd for years. TheB. pilosicolieradication plan was based on the general guidelines for elimination ofB. hyodysenteriae, with some modifica-tions. The eradication measures were run in August 1997. In-feed medication with 200p.p.m. tiamulin lasted for 18–30 days, depending on the age group. The piggery unit was emptied, cleaned, disinfected and dried, and all worn surfaces were repaired. The animals were removed to temporary sheds situated 0–100m from the piggery unit. Only the sows and the boar returned to the piggery unit. All other pigs were sold from the sheds within 3 months after the eradication. Immediately after the eradication, the clinical postweaning diarrhea disappeared. The success of the program was monitored four times bacteriologically, and the last control sampling was in December 1999, 7 months after the total withdrawal of antimicrobial feed additives. The primary cultures from the last three samplings were also analysed withB. pilosicoli-specific PCR. All the samples were negative forB. pilosicoli. However,B. innocenscould be isolated from each batch of samples. The analysis ofB. inno-censisolates by pulsed-field gel electrophoresis indicated that at least one genotype persisted in the herd. The clinical and laboratory findings suggest that the eradication ofB. pilosicolihad succeeded in this herd

Comparative evaluation of molecular assays for the identification of intestinal spirochaetes from diseased pigs

Rapid identification of porcine Brachyspira species is required in order to differentiate pathogenic from non-pathogenic species. The aim of our study was to compare a recently described genetic method based on polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP), nox RFLP-PCR assay, and three species-specific PCRs described previously in the literature with a 16S rRNA gene RFLP-PCR discriminatory reference assay (16S RFLP-PCR) for the identification of Brachyspira spp. of swine origin. In this study, 20 porcine spirochaetal strains were identified and compared to 33 reference strains by 16S RFLP-PCR and nox RFLP-PCR and three species-specific PCRs. RFLP-PCR methods showed concordant results for 47 strains and discordances for 6 strains (2 differently identified and 4 not revealed by nox RFLP-PCR). In our hands species-specific PCRs showed concordant results with 16S and nox RFLP-PCR for 43 strains and discordances for 10 strains (2 differently identified and 8 not amplified). The same results observed testing the 20 field-isolated spirochaetes were obtained for the corresponding porcine faecal samples. The detection limit was 10(2) -10(3) cells/g of faeces for 16S rRNA gene PCR and 10(4) cells/g of faeces for nox PCR. In our experience nox RFLP-PCR appeared successful for the speciation of B. hyodysenteriae reserving 16S RFLP-PCR for all other pathogenic and non-pathogenic Brachyspira species. Among the species-specific PCR assays tested only that for B. pilosicoli was useful in our hands.

Comparison of culture and biochemical tests with PCR for detection of Brachyspira hyodysenteriae and Brachyspira pilosicoli

Traditional culture and biochemical tests (CBT) were compared with PCR for sensitivity and detection of Brachyspira hyodysenteriae and Brachyspira pilosicoli in seeded faeces and clinical samples from diarrhoeic pigs. A duplex PCR system was developed based on primers detecting the tlyA-gene of B. hyodysenteriae and the 16S rRNA-gene of B. pilosicoli. Sensitivities for the PCR system were determined on seeded faeces, using DNA that had been recovered from primary cultures or extracted directly from faeces. Compared to CBT, PCR applied to DNA extracted directly from faeces lowered the sensitivity by a factor of 1000 to 10,000. B. hyodysenteriae and B. pilosicoli detection was compared for CBT and PCR using 200 clinical samples. CBT detected more B. hyodysenteriae isolates in the clinical samples than PCR, but fewer B. pilosicoli positive samples. An atypical strongly haemolytic isolate was detected only by CBT.

D-ribose utilisation differentiates porcine Brachyspira pilosicoli from other porcine Brachyspira species

D-ribose utilisation was studied in 60 Brachyspira pilosicoli strains and 35 strains of other Brachyspira species, the majority of which were of porcine origin. Utilisation of D-ribose was demonstrated indirectly by measuring the reduction in pH of densely inoculated tryptone-peptone broth supplemented with 7% foetal calf serum and 1% D-ribose. Among B. pilosicoli strains, the mean reduction in pH units was 1.72 (range 0.95-2.28) in broth with D-ribose and 0.27 (range 0.10-0.40) in sugar-free control broth. For Brachyspira strains other than B. pilosicoli, the corresponding reductions in pH units were 0.37 (range 0.12-0.49) and 0.37 (range 0.15-0.58). In conclusion, porcine B. pilosicoli can be differentiated from other porcine Brachyspira species by a test for D-ribose utilisation.

Neither hippurate-negative Brachyspira pilosicoli nor Brachyspira pilosicoli type strain caused diarrhoea in early-weaned pigs by experimental infection

A hippurate-negative biovariant of Brachyspira pilosicoli (B. pilosicoli^hipp-) is occasionally isolated in diarrhoeic pigs in Finland, often concomitantly with hippurate-positive B. pilosicoli or Lawsonia intracellularis. We studied pathogenicity of B. pilosicoli^hipp- with special attention paid to avoiding co-infection with other enteric pathogens. Pigs were weaned and moved to barrier facilities at the age of 11 days. At 46 days, 8 pigs were inoculated with B. pilosicoli^hipp- strain Br1622, 8 pigs were inoculated with B. pilosicoli type strain P43/6/78 and 7 pigs were sham-inoculated. No signs of spirochaetal diarrhoea were detected; only one pig, inoculated with P43/6/78, had soft faeces from day 9 to 10 post inoculation. The pigs were necropsied between days 7 and 23 after inoculation. Live pigs were culture-negative for Brachyspira spp., but B. pilosicoli^hipp- was reisolated from necropsy samples of two pigs. The lesions on large colons were minor and did not significantly differ between the three trial groups. In silver-stained sections, invasive spirochaetes were detected in colonic mucosae of several pigs in all groups. Fluorescent in situ hybridisation for genus Brachyspira, B. pilosicoli and strain Br1622 was negative. However, in situ detection for members of the genus Leptospira was positive for spirochaete-like bacteria in the colonic epithelium of several pigs in both infected groups as well as in the control group. L. intracellularis, Salmonella spp., Yersinia spp. and intestinal parasites were not detected. The failure of B. pilosicoli strains to cause diarrhoea is discussed with respect to infectivity of the challenge strains, absence of certain intestinal pathogens and feed and management factors.

Tiamulin resistance in porcine Brachyspira pilosicoli isolates

There are few studies on antimicrobial susceptibility of Brachyspira pilosicoli, therefore this study was performed to investigate the situation among isolates from pigs. The tiamulin and tylosin susceptibility was determined by broth dilution for 93 and 86 porcine B. pilosicoli isolates, respectively. The isolates came from clinical samples taken in Swedish pig herds during the years 2002 and 2003. The tylosin minimal inhibitory concentration (MIC) was >16 microg/ml for 50% (n=43) of the isolates tested. A tiamulin MIC >2 microg/ml was obtained for 14% (n=13) of the isolates and these were also tested against doxycycline, salinomycin, valnemulin, lincomycin and aivlosin. For these isolates the susceptibility to salinomycin and doxycycline was high but the MICs for aivlosin varied. The relationship between the 13 tiamulin resistant isolates was analyzed by pulsed-field gel electrophoresis (PFGE). Among the 13 isolates 10 different PFGE patterns were identified.

Amplification and sequencing of Brachyspira spp. specific portions of nox using paraffin-embedded tissue samples from clinical colitis in Austrian pigs shows frequent solitary presence of Brachyspira murdochii

Brachyspira infections are significant causes of enterocolitis in pigs. In order to differentiate pathogenic species (Brachyspira (Br.) hyodysenteriae, Brachyspira pilosicoli) from less pathogenic or non-pathogenic species (Brachyspira intermedia, Brachyspira innocens, Brachyspira murdochii) in paraffin-embedded tissue samples a polymerase chain reaction (PCR) protocol allowing identification of Brachyspira at species level in archival material was developed. This approach was complemented by sequencing of the PCR amplification products. All seven cases presented with clinical and morphological Brachyspira-associated enterocolitis. Br. hyodysenteriae was not identified in any of the cases, while Br. pilosicoli was identified in a single case in conjunction with Br. murdochii. One case each was found positive for Br. innocens and Br. intermedia. Interestingly, the majority of cases presented as single or double infections with Br. murdochii. In some of the pigs other pathogens, like porcine circovirus-2 or Lawsonia intracellularis were present. These observations point at the possibility that under certain conditions even Brachyspira species of low pathogenicity can multiplicate extensively and lead to Brachyspira-associated enterocolitis.

Assessment of diagnostics and antimicrobial susceptibility testing of Brachyspira species using a ring test

There is no ring test for quality assessment available in Europe for diagnostics and antimicrobial susceptibility testing of the fastidious, anaerobic bacteria of the genus Brachyspira. Therefore, an international ring test for Brachyspira spp. was performed once a year during 2002-2004. Two sets of coded samples were prepared and distributed on each occasion. One set comprised six swabs dipped in pig faeces spiked with Brachyspira spp. intended for diagnostics. The other set comprised two pure strains intended only for susceptibility testing. All methods used were in-house methods. The species used were Brachyspira hyodysenteriae, Brachyspira pilosicoli, Brachyspira innocens, Brachyspira murdochii and Brachyspira intermedia. In most cases, the correct Brachyspira spp. were detected. However, the results showed that Brachyspira spp. could be difficult to identify, especially if two Brachyspira spp. were mixed or if the concentration of Brachyspira in faeces was low. Additionally, some laboratories reported Brachyspira growth in control samples that were not seeded with any spirochaetes. The lowest detection level was 10(2) bacteria/ml faeces for both B. hyodysenteriae and B. pilosicoli. The susceptibility tests performed showed that disc diffusion was not recommendable for Brachyspira spp. Extended antimicrobial dilution series gave most congruent results. The diversity of the results highlights the importance of ring tests for a high quality of diagnostics and antimicrobial susceptibility tests for Brachyspira spp. This is the first ring test described for Brachyspira spp.

Antimicrobial resistance in Brachyspira pilosicoli with special reference to point mutations in the 23S rRNA gene associated with macrolide and lincosamide resistance

A point mutation in the 23S rRNA gene causes macrolide and lincosamide resistance in Brachyspira hyodysenteriae. The possible occurrence of a similar mutation in Brachyspira pilosicoli was studied and the MICs of six antimicrobial agents for Swedish field isolates of B. pilosicoli were determined. Of 10 isolates with high MICs of macrolide and lincosamide antibiotics, six had a mutation in nucleotide position 2058 or 2059 in the 23S rRNA gene as compared to the wild type of Escherichia coli, whereas none of 10 tylosin-susceptible isolates were mutated in this region. The mutations found in position 2058 were A --> T transversions, and in position 2059 either A --> G transitions or A --> C transversions. The MICs at which 90% of the B. pilosicoli field isolates were inhibited by tylosin, erythromycin, clindamycin, virginiamycin, tiamulin, and carbadox, were >256, >256, >4, 4, 2, and 0.125 microg/ml, respectively. In conclusion, point mutations in positions 2058 and 2059 of the 23S rRNA gene can cause macrolide and lincosamide resistance in B. pilosicoli. Macrolide resistance is widespread among Swedish field isolates of B. pilosicoli. Notably also a few isolates with elevated MICs of tiamulin were found.

Rapid isolation of Brachyspira hyodysenteriae and Brachyspira pilosicoli from pigs

The aim of this study was to compare and evaluate the time required to isolate Brachyspira hyodysenteriae and Brachyspira pilosicoli from porcine faeces. This was done using previously described selective media (spectinomycin) S400, (colistin, vancomycin and spectinomycin) CVS and (spectinomycin, vancomycin, colistin, spiramycin and rifampin with swine faecal extract) BJ, compared with the method based on blood agar modified medium, with spectinomycin and rifampin (BAM-SR), including a pre-treatment step. Fourteen spirochaetal strains were obtained in pure cultures after 5 days (48 h in BAM-SR primary plate and three passages every 24 h in brain heart infusion (BHI) without antibiotics) pre-treating simulated samples in brain heart infusion broth with spectinomycin (400 microg/ml) and rifampin (15 microg/ml), before streaking on the selective BAM-SR medium. Spirochaetes from samples in S400, CVS and BJ, with and without pre-treatment, were obtained in pure cultures only after repeatedly transferring on plates of the same selective medium requiring 15-18 days according to the strain. BAM-SR used after the pre-treatment step showed a detection limit ranging from 3.5 x 10(2) to 6.7 x 10(7) cells/g faeces and was the only method able to support the growth of spirochaetes after 48 h.

Molecular and ultrastructural characterization of porcine hippurate-negative Brachyspira pilosicoli

Brachyspira pilosicoli, the causative agent of porcine intestinal spirochetosis, usually has hippurate-cleaving capacity. We have regularly isolated hippurate-negative B. pilosicoli from cases of porcine diarrhea. In this study, we show that these biochemically atypical B. pilosicoli isolates can be classified as B. pilosicoli. 16S ribosomal DNA was partially sequenced from eight hippurate-negative and two hippurate-positive B. pilosicoli-like isolates from seven herds. The differences in nucleotide sequence with B. pilosicoli P43/6/78 type strain were not associated with hippurate cleavage. In 877 bp, the hippurate-negative isolates had a similarity of 98.63 to 100% to the type strain, with the corresponding figures for the two hippurate-positive isolates being 98.86 and 100%. The nucleotide sequences of hippurate-positive isolates were identical to the respective sequences of hippurate-negative isolates from one herd. The DNA macrorestriction patterns of a total of 20 hippurate-negative and -positive B. pilosicoli isolates were diverse, and no clustering in conjunction with the hippurate reaction was found. In two herds, hippurate-positive and -negative B. pilosicoli isolates had a common macrorestriction pattern. The ultrastructure of hippurate-negative isolates was similar to the type strain. In conclusion, B. pilosicoli can be either hippurate positive or negative and, thus, the scheme for biochemical differentiation of porcine Brachyspira should be revised to include identification of hippurate-negative B. pilosicoli.

Immunomagnetic separation of the intestinal spirochaetes Brachyspira pilosicoli and Brachyspira hyodysenteriae from porcine faeces

Porcine intestinal spirochaetes are fastidious anaerobic organisms and, as a consequence, it has been necessary to develop various protocols to enhance their isolation from or detection in faeces. Immunomagnetic separation (IMS) is a method developed recently to improve separation of target cells from mixed cell suspensions. The purpose of the present study was to compare the relative sensitivity of IMS for isolation of Brachyspira pilosicoli and Brachyspira hyodysenteriae with current routine diagnostic methods (culture on selective media and PCR) for detection of these micro-organisms in pig faeces. Neither direct nor indirect IMS methods enhanced the sensitivity of detection of either organism when performed with the recommended washings during sample processing. Performance of the IMS procedure without washing gave sensitivity at levels similar to direct culture onto selective medium. Further development of IMS techniques is required to improve isolation rates of Brachyspira species from faecal samples.

Further characterization of porcine Brachyspira hyodysenteriae isolates with decreased susceptibility to tiamulin

Brachyspira hyodysenteriae is the causative agent of swine dysentery, a severe diarrhoeal disease in pigs. Few drugs are available to treat the disease, owing to both antimicrobial resistance and withdrawal of drugs authorized for use in pigs. Tiamulin is the drug of choice in many countries, but isolates with decreased susceptibility have recently been reported. The mechanism of tiamulin resistance in B. hyodysenteriae is not known and this facet is essential to understand the dissemination of the trait. To study the resistance epidemiology of B. hyodysenteriae, further characterization of a set of isolates from Germany (n = 16) and the UK (n = 6) with decreased susceptibility to tiamulin was performed. The relatedness between the isolates was studied by comparing PFGE patterns, and the in vitro susceptibility to five other antimicrobials (aivlosin, doxycycline, salinomycin, chloramphenicol and avilamycin) was also determined. For comparison of the antimicrobial-susceptibility pattern, Swedish (n = 20) and British (n = 4) tiamulin-susceptible isolates were tested. The German isolates represented several different PFGE patterns, indicating that tiamulin usage has been sufficient to select clones with decreased tiamulin susceptibility at different farms in Germany. The PFGE pattern for the six British isolates with decreased tiamulin susceptibility was identical to that of the German isolates, and they had a similar antimicrobial-susceptibility pattern, except for resistance to aivlosin, which was only found in a few German isolates. No other co-resistance with tiamulin was found.

Human intestinal spirochaetosis: any clinical significance?

Spirochaetes are well known causative agents of diarrhoea in veterinary medicine. In human medicine the relationship between presence of spirochaetes in the colon on the one hand, and its clinical significance on the other, is far less clear. In the majority of cases the colonization of the colon with these micro-organisms seems to represent a commensal relationship with the host, and is almost always a coincidental finding with no association with the clinical symptoms of the patient whatsoever. Very infrequently the organism may become invasive. In this article the literature on human intestinal spirochaetosis is reviewed, and key points for daily clinical practice are emphasized.

Development of a duplex PCR assay for detection of Brachyspira hyodysenteriae and Brachyspira pilosicoli in pig feces

A duplex PCR (D-PCR) amplifying portions of the Brachyspira hyodysenteriae NADH oxidase gene and the B. pilosicoli 16S rRNA gene was developed and then tested on DNA extracted from 178 porcine fecal samples. The feces also underwent anaerobic culture and species-specific PCRs. Fecal extraction-D-PCR detected seven additional samples containing B. hyodysenteriae and five more containing B. pilosicoli.

Differentiation of porcine Brachyspira species by a novel nox PCR-based restriction fragment length polymorphism analysis

A novel PCR-based restriction fragment length polymorphism analysis of the Brachyspira nox gene was developed. The restriction patterns for Brachyspira hyodysenteriae, B. pilosicoli, B. intermedia, B. murdochii, and B. innocens were highly distinct with two restriction endonucleases only. The assay proved to be user-friendly and robust.

A novel method for isolation of Brachyspira (Serpulina) hyodysenteriae from pigs with swine dysentery in Italy

Brachyspira (Serpulina) hyodysenteriae was isolated from 10 of 11 pigs with clinically suspected swine dysentery in six herds in northern Italy. All strains were successfully isolated in the selective blood agar modified medium with spectinomycin and rifampin (BAM-SR) currently used in our laboratory to isolate B. (S.) pilosicoli of human origin, after pre-treatment of intestinal material with spectinomycin and rifampin in foetal calf serum. Isolates had phenotypic characteristics typical of B. (S.) hyodysenteriae.

Brachyspira aalborgi infection diagnosed by culture and 16S ribosomal DNA sequencing using human colonic biopsy specimens

In this study we report on the isolation and characterization of the intestinal spirochete Brachyspira aalborgi using human mucosal biopsy specimens taken from the colon of a young adult male with intestinal spirochetosis. A selective medium, containing 400 microg of spectinomycin/ml and 5 microg of polymyxin/ml was used for the isolation procedure. A high degree of similarity, in terms of phenotypic properties and 16S ribosomal DNA sequence, was observed between the isolated strain, named W1, and the type strain, 513A, of B. aalborgi. A similarity of 99.7% in the nucleotide sequence was found between W1 and 513A(T), based on the almost-complete gene. A short segment of the 16S rRNA gene was amplified by PCR using genetic material enriched from paraffin-embedded biopsy specimens, which were taken from the patient on two occasions. The products showed 16S rRNA gene sequences virtually identical to that of strain 513A(T) in the actual region. Immunohistochemistry was performed on the colonic biopsy specimens with a polyclonal antibody raised against an intestinal spirochete isolated in a previous case of human intestinal spirochetosis. The antibody reacted strongly with the spirochete on the luminal epithelium. No immune reaction was seen within or below the surface epithelium. Routine histology did not reveal signs of colitis. Electron microscopy showed spirochetes attached end-on to the colonic mucosal surface. The isolate grew poorly on a commonly used selective medium for intestinal spirochetes, which may explain previous failures to isolate B. aalborgi.

Cloning and DNA sequence analysis of an immunogenic glucose-galactose MglB lipoprotein homologue from Brachyspira pilosicoli, the agent of colonic spirochetosis

Colonic spirochetosis (CS) is a newly emerging infectious disease of humans and animals caused by the pathogenic spirochete Brachyspira (formerly Serpulina) pilosicoli. The purpose of this study was to characterize an antigen that was recognized by antibodies present in sera of challenge-exposed pigs. The gene encoding the antigen was identified by screening a plasmid library of human B. pilosicoli strain SP16 (ATCC 49776) genomic DNA with hyperimmune and convalescent swine sera. The predicted amino acid sequence encoded by the cloned B. pilosicoli gene had a high degree of similarity and identity to glucose-galactose MglB lipoprotein. Located 106 bp downstream of the putative mglB gene was a 3'-truncated open reading frame with 73.8% similarity and 66.3% identity to mglA of Escherichia coli, suggesting a gene arrangement within an operon which is similar to those of other bacteria. A single copy of the gene was present in B. pilosicoli, and homologous sequences were widely conserved among porcine intestinal spirochetes Serpulina intermedia, Brachyspira innocens, Brachyspira murdochii, and the avian Brachyspira alvinipulli, but not in porcine Brachyspira hyodysenteriae, human Brachyspira aalborgi, and porcine Treponema succinifaciens. The deduced molecular weight of the mature MglB lipoprotein was consistent with expression by the cloned gene of a polypeptide with an apparent molecular weight of 36,000, as determined by Western blot analysis and [(3)H]palmitate labeling. Because mucin is the principal constituent of the colonic mucus gel and consists of glycoproteins that can serve as the substrate for growth and chemotaxis of B. pilosicoli in vitro, a role for MglB in mucosal localization of the spirochete appears consistent with the pathogenesis of CS. However, the presence of homologous sequences in closely related but nonpathogenic commensal spirochetes suggests that other virulence determinants may be required for pathogenesis.

Identification of porcine intestinal spirochetes by PCR-restriction fragment length polymorphism analysis of ribosomal DNA encoding 23S rRNA

The Brachyspira (formerly Serpulina) species rrl gene encoding 23S ribosomal RNA (rRNA) was used as a target for amplification of a 517bp DNA fragment by polymerase chain reaction (PCR). The primers for PCR amplification had sequences that were conserved among Brachyspira 23S rRNA gene and were designed from nucleotide sequences of Brachyspira hyodysenteriae, Serpulina intermedia, Brachyspira innocens and Brachyspira pilosicoli available from the GenBank database. Digestion of PCR-generated products from reference and field isolates of swine intestinal spirochetes with restriction enzymes Taq I and Alu I revealed five restriction fragment length polymorphism (RFLP) patterns. Each RFLP pattern corresponded to previously established genetic groups including B. hyodysenteriae (I), S. intermedia/B. innocens (II), Brachyspira murdochii (III), B. pilosicoli (IV) and B. alvinipulli (V). The 23S rRNA PCR/RFLP provided a relatively simple genotypic method for identification of porcine pathogenic B. hyodysenteriae and B. pilosicoli.

Comparative pathology of bacterial enteric diseases of swine

Enteric bacterial infections are among the most common and economically significant diseases affecting swine production worldwide. Clinical signs of these infections include diarrhea, reduced growth rate, weight loss, and death of preweaned, weanling, grower-finisher, young and adult age breeding animals. The most common etiological agents include Escherichia coli, Clostridium perfringens, Lawsonia intracellularis, Salmonella enterica, and Brachyspira (Serpulina) spp. With the exception of Brachyspira (Serpulina) hyodysenteriae, the cause of swine dysentery, and Lawsonia intracellularis, the cause of proliferative enteropathy, the pathological changes seen with these agents closely resemble the diseases occurring in human beings. Histological changes in the intestines of swine with enteric bacterial infections include bacterial colonization without significant damage (e.g., certain enterotoxigenic E. coli and C. perfringens type A), attaching and effacing lesions with enteropathogenic E. coli and Brachyspira pilosicoli, the cause of colonic spirochetosis, inflammation with S. enterica, and necrotizing and hemorrhagic lesions with certain C. perfringens. Extraintestinal spread of bacteria and/or toxins occurs with some serotypes of E. coli and most serotypes of S. enterica. Enteric bacterial diseases of swine have been used as models to study the pathogenesis of similar diseases of human beings. Several of these pathogens are also important causes of food-borne disease in humans.

Prevalence of Brachyspira species isolated from diarrhoeic pigs in Brazil

Pathogenic intestinal spirochaetes of pigs include Brachyspira (formerly Serpulina) hyodysenteriae, the cause of swine dysentery, and Brachyspira pilosicoli, the cause of porcine colonic spirochetosis (PCS). The purpose of this study was to assess the relative importance of Brachyspira species in diarrhoeal disease of growing pigs on farms in southern Brazil. The intensity and pattern of haemolysis, the production of indole and the hydrolysis of hippurate by reference and field porcine intestinal spirochaetes were compared with 16S-ribosomal RNA (mRNA)- and 23S-rRNA-based polymerase chain reaction assays for the identification of B hyodysenteriae and B pilosicoli. Between July and October 1998, 206 rectal swabs were taken from pigs on 17 farms with a history of diarrhoea developing within 30 days after they had been moved from nursery to growing facilities. Of 49 beta-haemolytic spirochaetes that were cultured, 29 (59.2 per cent) were grown in pure culture for phenotypic and genotypic characterisation, leaving 20 untyped. Of the 29 typed isolates, eight isolates obtained from six farms were identified as B hyodysenteriae, and 15 isolates obtained from seven other farms were identified as B pilosicoli; the remaining six isolates were identified as weakly beta-haemolytic commensal spirochaetes. There was complete agreement between the results of the phenotypic and genotypic analyses.

Detectability and prevalence of Brachyspira species in herds rearing health class feeder pigs in Finland

Faeces samples were taken three times at two-week intervals, from the farrowing units of four herds of known Brachyspira (formerly Serpulina) status and one of unknown Brachyspira status. Brachyspira hyodysenteriae, Brachyspira pilosicoli, Brachyspira intermedia and Brachyspira group III were isolated from the faecal samples from the weaners in the herds using either a maximum of 50 ppm of olaquindox or no feed additives. The detection rates were relatively consistent. However, B hyodysenteriae was not detected at one sampling in a known positive herd. The prevalence of Brachyspira species was also studied in feeder pigs originating from LSO 2000 health class farrowing units, comparable with specific pathogen-free herds. These farms were free from swine dysentery, sarcoptic mange, swine enzootic pneumonia and progressive atrophic rhinitis. Fifty of 428 herds were sampled once. B hyodysenteriae was not isolated from any of them, but B intermedia, B pilosicoli and Brachyspira group III were isolated from five, 14 and 37 of the herds, respectively. The detection of Brachyspira species did not relate to the prevalence of diarrhoea in the herds, as judged by the farmers. The herds using carbadox (40 to 50 ppm) had a lower prevalence of Brachyspira species than those using olaquindox (40 to 50 ppm).

Diarrhea in growing-finishing swine

Regardless of the etiology of an enteric disease in nursery age to finisher swine, making a prompt and accurate diagnosis is crucial. Eliciting a complete history, assessing clinical signs and pathology, and selecting and interpreting laboratory tests are essential components in achieving this. Early detection and diagnosis of enteric disease is particularly critical in the nursery through finisher phase because of economic impacts. Recurrent topics when discussing control and prevention of enteric diseases are reducing stress and improving pig comfort and reducing or eliminating exposure through sanitation and biosecurity. These are not new concepts; in fact, prior to the advent of antimicrobials, they were the mainstay of treatment of enteric diseases. With concern over the use of antimicrobials in food animal production increasing, exploiting disease ecology to control enteric diseases is increasing in importance. New vaccines and bacterins for postweaning swine enteric diseases are needed tools to exploit the pig's immune system. Recent advances in diagnostic capabilities allow an increase in understanding and exploitation of disease ecology.

Scanning electron microscopy and fluorescent in situ hybridization of experimental Brachyspira (Serpulina) pilosicoli infection in growing pigs

Two groups of six 8-week-old pigs were challenged with 1x10(9) cfu Brachyspira (Serpulina) pilosicoli or Serpulina intermedia daily for 3 consecutive days to study the pathology of porcine colonic spirochetosis by scanning electron microscopy (SEM) and fluorescent in situ hybridization (FISH) with oligonucleotide probes targeting ribosomal RNA specific for B. pilosicoli and the genus Brachyspira/Serpulina. Six pigs served as noninoculated controls. The animals were euthanatized successively between postinoculation days 14 and 24. B. pilosicoli was reisolated in feces from all of the inoculated pigs; however, only two pigs developed transient watery diarrhea. S. intermedia was reisolated from four of the inoculated pigs, but clinical signs were not observed. Gross examination of the B. pilosicoli-infected pigs revealed dilated large intestines with a hyperemic mucosa, whereas the large intestines of the S. intermedia-inoculated pigs and the control pigs appeared normal. SEM examination of B. pilosicoli-infected pigs revealed degenerated epithelial cells and spirochetal colonization of the colonic mucosa in four pigs. By FISH, B. pilosicoli cells were found colonizing and invading the surface epithelium and the crypts in all the pigs. Spirochetal crypt colonization markedly exceeded the occurrence of spirochetes on the mucosal surface. SEM examination of S. intermedia-inoculated pigs revealed no abnormalities, and Serpulina cells were detected only sporadically in the otherwise normal-appearing mucosa of four pigs by FISH. The results provide further evidence that B. pilosicoli is associated with colitis in pigs, although the gross lesions are mild. The spirochete is capable of colonizing the large intestine, inducing mucosal damage, invasion of the crypt and surface epithelium, and focal infiltration of the lamina propria. In addition, the study shows the applicability of FISH for specific identification of B. pilosicoli in formalin-fixed tissue.

Emended descriptions of indole negative and indole positive isolates of Brachyspira (Serpulina) hyodysenteriae

Two type/reference strains of Brachyspira (B.) hyodysenteriae, 14 Belgian and German indole negative, and 14 Belgian, German and Swedish indole positive field isolates of strongly beta-haemolytic intestinal spirochaetes were compared by pulsed-field gel electrophoresis (PFGE) patterns, biochemical reaction patterns, 16S rDNA sequences and MIC determinations of six antibacterial substances. Three tests for indole production, including a spot indole test, were compared with congruent results. All field isolates were classified as B. hyodysenteriae due to a high genetic and phenotypic similarity with the type strains. The Belgian and German indole negative isolates had identical and unique PFGE patterns for the tested restriction enzymes MluI and SalI, as well as identical 16S rDNA sequences, and they could not be differentiated by any of the methods used. Seven unique PFGE patterns were achieved from the 14 indole positive field isolates. The patterns were identical and unique for epidemiologically related isolates. Type/reference strains and isolates without known relation to other tested isolates showed unique banding patterns. The MICs of tylosin, tiamulin, erythromycin, clindamycin, carbadox and virginiamycin were determined in broth for all isolates. In contrast to Belgian and German isolates, the majority of the Swedish field isolates were susceptible to tylosin, erythromycin and clindamycin. Probable pathways of infection for some of the Swedish isolates were determined. The PFGE patterns of epidemic clones of B. hyodysenteriae remained stable for a period of up to 8 years. In vivo development of resistance to macrolide and lincosamide antibiotics due to use of tylosin was clearly indicated for two epidemic clones.

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

The NADH oxidase genes (nox) of 18 strains of intestinal spirochaetes were partially sequenced over 1246 bases. Strains examined included 17 representatives from six species of the genus Serpulina, and the type strain 513A(T) of the human intestinal spirochaete Brachyspira aalborgi. Sequences were aligned and used to investigate phylogenetic relationships between the organisms. Nox sequence identities between strains within the genus Serpulina were within the range 86.3-100%, whilst the nox gene of B. aalborgi shared between 78.8-83.0% sequence identity with the nox sequences of the various Serpulina strains. A phenogram produced based on sequence dissimilarities was in good agreement with the current classification of species in the genus Serpulina, although an atypical strongly beta-haemolytic porcine strain (P280/1), previously thought to be S. innocens, appeared distinct from other members of this species. Primer pairs were developed from the nox sequence alignments for use in polymerase chain reaction (PCR) identification of the pathogenic species S. hyodysenteriae (NOX1), S. intermedia (NOX2), and S. pilosicoli (NOX3), and for the combined non-pathogenic species S. innocens and S. murdochii (NOX4). The PCRs were optimised using 80 strains representing all currently described species in the genus Serpulina, as well as the type strain of B. aalborgi. Tests NOX1 and NOX4 specifically amplified DNA from all members of their respective target species, whilst tests NOX2 and NOX3 were less sensitive. NOX2 amplified DNA from all 10 strains of S. intermedia from pigs but from only 4 of 10 strains from chickens, whilst NOX3 amplified DNA from only 18 of 21 S. pilosicoli strains, even at low stringency. Tests NOX1 and NOX4 should prove useful in veterinary diagnostic laboratories, whilst NOX2 and NOX3 require further refinement.