Development of a multiplex-PCR for rapid detection of the enteric pathogens Lawsonia intracellularis, Brachyspira hyodysenteriae, and Brachyspira pilosicoli in porcine faeces

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.

Fecal PCR survey and genome analysis of Lawsonia intracellularis in China

Proliferative enteropathy caused by Lawsonia intracellularis is an important economic associated disease to pig industry, but the knowledge about the prevalence of L. intracellularis in pig farms in China is limited. In addition, there is no complete genome sequence available for L. intracellularis isolates from China. In this study, we developed a TaqMan qPCR for the screening of L. intracellularis by targeting the bacterial 16S rDNA gene. Laboratory evaluations revealed a good sensitivity and specificity on detecting L. intracellularis nucleic acid. Using this method, we investigated 891 fecal samples from apparently healthy pigs in 47 farms. The results demonstrated a screening positive rate of 37.3% (95% CI, 34.1-40.5%) for the samples, and a farm screening positive rate of 93.6% (95% CI, 65.3-94.4%). The screening positive rate at herd level ranged from 6.67% (95% CI, 0.2-31.9%) to 40% (95% CI, 38-79.6%), while at animal level, the highest screening positive rate was found in 12-week-old pigs [85.7% (95% CI, 67.3-96.0%)]. Investigation of 705 diarrheal or bloody feces from symptomatic pigs revealed that the highest positive rate was found in replacement gilts which was 37.18% (95% CI, 45.1-89.5%). Secondly, we conducted the complete genome sequence of a L. intracellularis PPE-GX01-2022 from China through PacBio sequencing. The genome of PPE-GX01-2022 consisted of a chromosome of 1,439,110 bp in length and three plasmids of 193,063, 39,799, and 27,067 bp, respectively. This genome encoded 1,428 predicted proteins, 44 tRNAs, and 6 rRNAs. Sequence comparisons demonstrated that the genome sequence of PPE-GX01-2022 was highly homologous to those of two isolates from US, and these three isolates shared 1,378 core genes. The screening results suggest a high prevalence rate of L. intracellularis in Chinese pig farms. In addition, the genome sequence of the Chinese isolate was highly homologous to those of the field isolates from the US.

Detection of mcr-1-1 Positive Enteropathogenic Escherichia coli Isolates Associated with Post-Weaning Diarrhoea in an Organic Piglet-Producing Farm in Austria

Postweaning diarrhoea (PWD) is a frequent multifactorial disease occurring in swine stocks worldwide. Since pathogenic Escherichia (E.) coli play a pivotal role in the pathogenesis of PWD and porcine E. coli are often resistant to different antibiotics, colistin is frequently applied to treat piglets with PWD. However, the application of colistin to livestock has been associated with the emergence of colistin resistance. This case report describes the detection of the colistin resistance gene mcr-1-1 in two E. coli isolated from piglets with PWD in an Austrian organic piglet-producing farm, which was managed by two farmers working as nurses in a hospital. Both mcr-1-positive E. coli were further analysed by Illumina short-read-sequencing, including assemblies and gene prediction. Both isolates belonged to the same clonal type and were positive for eaeH and espX5, which are both virulence genes associated with enteropathogenic E. coli (EPEC). Due to the detection of mcr-1-positive EPEC and based on the results of the antimicrobial resistance testing, the veterinarian decided to apply gentamicin for treatment instead of colistin, leading to improved clinical signs. In addition, after replacing faba beans with whey, PWD was solely observed in 2/10 weaned batches in the consecutive months.

Severe Colitis with Portal Venous Gas Caused by Brachyspira pilosicoli Infection

We herein report a case of Brachyspira pilosicoli-caused severe colitis presenting with portal venous gas. A 75-year-old man was admitted because of a fever, severe abdominal pain and bloody diarrhea. He was negative for anti-HIV antibodies. He had been in close contact with a dog earlier. Abdominal computed tomography detected severe wall-thickening and fat-stranding of the entire colon accompanied by portal venous gas. A smear examination of his stool showed many Gram-negative spiral rods, suggesting intestinal spirochetosis. A polymerase chain reaction assay using stool samples detected an amplified band specific for B. pilosicoli. He responded well to antimicrobial agents including metronidazole.

Listeriosis in fattening pigs caused by poor quality silage - a case report

Background

Listeria (L.) monocytogenes as the causative agent of listeriosis in humans and different animal species, has its reservoir in the environment. It can be found in the gut and faeces of healthy pigs, but under certain circumstances it may cause clinical disease. Fatteners are usually not known to get affected by Listeria-associated septicaemia and enteritis. This case report shows, that L. monocytogenes should be part of the list of differential diagnoses, when fattening pigs suffer from haemorrhagic diarrhoea and septicaemia.

Case presentation

Here, we report of an episode of fatal listeriosis in fattening pigs in a piglet producing farm in Lower Austria, which was combined with a fattening unit with space for 450 fatteners. The mortality rate resulted in 7.8% among fattening pigs after suffering from clinical symptoms such as anorexia, bloody diarrhoea and increased body temperature. Two fattening pigs with clinical symptoms and maize silage samples were used for further diagnostics. L. monocytogenes were isolated from serosa samples of the pigs and in the corresponding fed maize silage. One animal was positively tested for Brachyspira hyodysenteriae, which may have also been involved in the development of colitis. Immunohistochemically, L. monocytogenes could be detected in high amounts in lymphatic tissue of the gut. Molecular biological characterisation of the L. monocytogenes isolates from pigs and maize silage resulted in an identical DNA-fingerprint assigned to sequence type (ST) 21. Additionally, a high content of deoxynivalenol (3000 parts per billion) was found in maize silage. Therefore, the maize silage produced under inappropriate ensilaging conditions in a silo, was most likely the source of infection. Antimicrobial therapy with amoxicillin led to a fast cure of the remaining affected fatteners.

Conclusion

To conclude, we were able to show, that L. monocytogenes can cause clinical disease in finishing pigs, which may have been a result of immunosuppression due to high deoxynivalenol exposure. When feeding silage it is important that all ensilaging procedures occur under appropriate anaerobic conditions to guarantee suppression of listerial growth.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1687-6) contains supplementary material, which is available to authorized users.

Ex vivo penetration of fosfomycin into healthy and Lawsonia intracellularis-colonized swine intestinal mucosa

Fosfomycin (FOS) is an antibiotic used, mostly in Latin America, for the treatment of lung and enteric infections of pigs. Intracellular fluids of enterocytes can act as biophase for Lawsonia intracellularis, the causative agent of porcine proliferative enteropathy (PPE). The aim of this study was to determine whether the presence of L. intracellularis in the enterocytes modifies FOS penetration. Eight healthy pigs in growth-finishing stage were used to produce healthy (group A) and L. intracellularis-colonized (group B) intestinal explants. For both groups, treatment consisted of a 580 μg/ml concentration of calcium FOS, which was added to each explant (0.5-6 hr). For group B, the Enterisol Ileitis^® vaccine was used as source of the micro-organism. Previously to the assay, the time necessary for L. intracellularis to colonize the enterocytes was defined. Also, a PCR protocol was optimized to determine the presence of the pathogen in the explants. There were nonstatistical differences for the penetration of the antibiotic into healthy and L. intracellularis-colonized enterocytes. MIC₉₀ of FOS for L. intracellularis is unknown; nevertheless, MIC₉₀ of various antibiotics ranges between 0.125 and 128 μg/ml. FOS reaches inside the enterocyte concentrations which surpass the MICs₉₀ of other antibiotics that also act by the inhibition of cell wall synthesis; however, further studies should be carried out to determine fosfomycin MIC₉₀ for L. intracellularis to discern the usefulness of this antibiotic in the treatment of PPE.

The Efficacy of Two Phytogenic Feed Additives in the Control of Swine Dysentery

Control of swine dysentery with antibiotics is often ineffective due to the resistance of Brachyspira hyodysenteriae. The potential of some herbal-based components against B. hyodysenteriae was previously studied in vitro. This study aims at the evaluation of in vivo efficacy of phytogenic feed additives in the control of swine dysentery

The study involved 64 seven-week old weaned pigs allotted to 4 groups: two were fed on feed supplemented with either Patente Herba® or Patente Herba® Plus, the third received tiamulin (positive control), while the negative control was not given antibiotics or additives. Fecal consistency was recorded daily. The presence of B. hyodysenteriae in the feces was investigated weekly using microbiological assays and the PCR test. Weight gain and feed conversion ratio were calculated for each week, and for the whole experiment.

B. hyodysenteriae was detected in all samples by both methods. The additives showed efficacy in the prevention and control of swine dysentery as only normal and soft stool was observed in the treated groups. By contrast, in the negative control all feces categories were detected. Frequencies of feces categories significantly differed (p<0.001) between feed-supplemented groups and the negative control. Efficacy of both additives in the prevention of SD is comparable to tiamulin, based on insignificant differences in the frequency of the various feces categories.

Beneficial effects of both additives resulted in significantly (p≤0.05) higher weight gain and lower feed conversion ratio in comparison to the negative control. The average weight gains between additive-fed groups and tiamulin-treated group did not differ significantly.

A real-time loop-mediated isothermal amplification method for rapid detection of Lawsonia intracellularis in porcine fecal samples

Porcine proliferative enteritis is a common diarrheal disease characterized by thickening of the intestinal mucosa in swine due to enterocyte proliferation, which is caused by Lawsonia intracellularis. In this study, a real-time loop-mediated isothermal amplification (LAMP) assay was developed to detect L. intracellularis based on the conserved region of the 16S ribosomal RNA gene. The optimal reaction conditions of the real-time LAMP was 65 °C for 60 min. The LAMP products could be detected by both real-time turbidity and direct visual inspection. The assay was specific for L. intracellularis, as no cross-reaction was observed with other pathogens. The detection limit of the real-time LAMP assay was 1.4 × 10^-1pg of L. intracellularis DNA, which was the same as that of real-time PCR and approximately 100 times more sensitive than that of conventional PCR. Of the 136 clinical samples, L. intracellularis DNA was identified in 60 samples by real-time LAMP, which was the same as real-time PCR and higher than conventional PCR (36.8%, 50/136). The specific, sensitive and rapid real-time LAMP assay developed in this study could be a useful alternative tool in point-of-care (POC) diagnosis of L. intracellularis infection.

Systemic cytokine response in pigs infected orally with a Lawsonia intracellularis isolate of South Korean origin

In the swine industry, Lawsonia intracellularis is one of the main enteric pathogens; it causes acute intestinal hemorrhage (proliferative hemorrhagic enteropathy) in naïve adult pigs and a wasting disease (proliferative enteropathy) in growing pigs. Among many kinds of cytokines, interferon-γ (IFN-γ) has previously been reported to play a significant role in limiting intracellular infection and increasing cellular proliferation associated with L. intracellularis. However, the levels of various circulating inflammatory cytokines, including IFN-γ, in animals infected with L. intracellularis is still an area of considerable interest for understanding immunity against this bacterium. In addition, there has been no information on cytokine response in animals infected with any L. intracellularis isolate of South Korean origin or Asian origin. To determine the relationship between the changes in the systemic inflammatory cytokine response in the peripheral blood of the host after L. intracellularis infection, we measured the levels of some pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IFN-γ), anti-inflammatory cytokines (IL-4, IL-10, and transforming growth factor-β (TGF-β)), and a chemokine (IL-8) in pigs infected with L. intracellularis isolated from South Korea. This study demonstrated that a L. intracellularis isolate of South Korean origin induced cytokine (TNF-α, IL-6, and IFN-γ) responses in infected animals within 15 days post-infection although the circulating levels of IL-4, IL-10, IL-8 and TGF-β were induced relatively late.

Brachyspira hyodysenteriae detection in the large intestine of slaughtered pigs

Detection of subclinical Brachyspira hyodysenteriae infection in pig herds using feces is challenging. However, the ability to detect the pathogen in intestinal samples of slaughtered pigs has not been investigated, to our knowledge. Therefore, we determined the detection of B. hyodysenteriae in the colon, cecum, and rectum from slaughtered pigs. We analyzed the correlation between detection rates and intestinal lesions, ingesta or fecal consistency, and time from sample collection until processing. A total of 400 ingesta-mucosal (colon, cecum) and 200 fecal (rectum) samples from 200 pigs originating from 20 different herds were bacteriologically examined using selective culture followed by Brachyspira spp. identification by PCR and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Ingesta or fecal consistency and intestinal lesions were scored. Brachyspira hyodysenteriae was detected in 23 samples from 16 intestines originating from 7 herds. Brachyspira spp. were detected in 96 samples. More intestinal (16) than fecal (7) samples tested positive for B. hyodysenteriae. For Brachyspira spp., this difference was significant (69 vs. 27; p < 0.01). In particular, colon samples tested positive ( n = 42, p = 0.06). Most (91%) of the intestines showed no lesions typical for clinical B. hyodysenteriae infection, and median ingesta or fecal consistency was "soft and formed," indicating subclinical infection, colonization, or absence of infection. Ingesta from slaughtered pigs, in particular from the colon and sites with lesions, is useful material for detection of B. hyodysenteriae.

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

AIMS

To evaluate and compare the capabilities of multilocus sequence typing (MLST) and multiple locus variable number tandem repeat analysis (MLVA) techniques to characterize Brachyspira hyodysenteriae isolates and to investigate the relationship between pleuromutilin resistance and genetic variability.

METHODS AND RESULTS

MLST genotyping was performed on 180 B. hyodysenteriae isolates, and the results were evaluated considering profiles from 108 other strains previously reported in the database. In total, 37 sequence types were obtained. The MLVA approach completely characterized 172 strains and grouped the isolates into 22 different profiles. The combination of MLST and MLVA showed a slight increase in the discriminatory power, identifying 33 joint profiles. An antibiotic resistance analysis showed a reduction in the susceptibility to pleuromutilins over time, and a weak association between susceptibility to valnemulin and inclusion in clonal complex 4.

CONCLUSION

MLST and MLVA are reliable methods for characterizing B. hyodysenteriae strains and they have comparable discriminatory power.

SIGNIFICANCE AND IMPACT OF THE STUDY

The genotyping of B. hyodysenteriae isolates and a database of all the genetic profiles collected during the diagnostic activities could support traditional epidemiological investigations in identifying infection sources and routes of transmission among herds, and in developing more effective control measures.

A novel multiplex qPCR targeting 23S rDNA for diagnosis of swine dysentery and porcine intestinal spirochaetosis

Background

A multiplex qPCR targeting a 128 bp region on the 23S rDNA gene was developed for detection of Brachyspira (B.) hyodysenteriae and B. pilosicoli, the agents of swine dysentery (SD) and porcine intestinal spirochaetosis (PIS), together with a triplet of apathogenic Brachyspira spp. (B. innocens, B. intermedia, B. murdochii) in porcine feces. The multiplex qPCR was evaluated against a duplex PCR (La et al., J Clin Microbiol 41:3372–5, 2003).

Results

Using DNA extracted from fecal culture, the multiplex qPCR showed excellent agreement with the duplex PCR (κ = 0.943 and 0.933). In addition, thanks to the three probes whereof one detecting the apathogenic Brachyspria spp., a more diversified overview of the brachyspiral flora in porcine fecal samples can be delivered as a part of the routine diagnostic. The multiplex qPCR with a limit of detection of 5–10 genomic equivalents (GE) per reaction (6 × 10² GE per gram) allows reliable detection of Brachyspira species directly from fecal swab DNA. In line with this, analysis of 202 fecal swabs in comparison with culture-based qPCR showed a high agreement for the causative agents of SD (B.hyodysenteriae: κ = 0.853, sensitivity 87% specificity 98%).

Conclusion

The novel multiplex qPCR is robust and has a high analytical sensitivity and is therefore suitable for high-throughput screening of porcine fecal swabs for the causative agents of SD. This assay can therefore be used for the direct proof of the pathogenic B. spp. in fecal swabs within the scope of a monitoring program.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0939-6) contains supplementary material, which is available to authorized users.

The Exposed Proteomes of Brachyspira hyodysenteriae and B. pilosicoli

Brachyspira hyodysenteriae and Brachyspira pilosicoli are well-known intestinal pathogens in pigs. B. hyodysenteriae is the causative agent of swine dysentery, a disease with an important impact on pig production while B. pilosicoli is responsible of a milder diarrheal disease in these animals, porcine intestinal spirochetosis. Recent sequencing projects have provided information for the genome of these species facilitating the search of vaccine candidates using reverse vaccinology approaches. However, practically no experimental evidence exists of the actual gene products being expressed and of those proteins exposed on the cell surface or released to the cell media. Using a cell-shaving strategy and a shotgun proteomic approach we carried out a large-scale characterization of the exposed proteins on the bacterial surface in these species as well as of peptides and proteins in the extracellular medium. The study included three strains of B. hyodysenteriae and two strains of B. pilosicoli and involved 148 LC-MS/MS runs on a high resolution Orbitrap instrument. Overall, we provided evidence for more than 29,000 different peptides pointing to 1625 and 1338 different proteins in B. hyodysenteriae and B. pilosicoli, respectively. Many of the most abundant proteins detected corresponded to described virulence factors and vaccine candidates. The level of expression of these proteins, however, was different among species and strains, stressing the value of determining actual gene product levels as a complement of genomic-based approaches for vaccine design.

The prevalence of swine enteropathogens in Brazilian grower and finish herds

Diarrhoea among growing and finishing pigs is an important problem in many herds. The prevalence of L. intracellularis, B. pilosicoli, B. hyodysenteriae, Salmonella spp., enterotoxigenic E. coli, Trichuris suis and the occurrence of mixed infection were investigated. Fecal samples for forty-six herds with diarrhea or a history of diarrhea were randomly collected in Minas Gerais state, Brazil. The enteric pathogens were detected by culture (E. coli and Salmonella sp.), PCR (L. intracellularis and Brachyspira spp.) and eggs counts (T. suis). The overall herd prevalence of L. intracellularis, Salmonella enterica serotype Typhimurium and enterotoxigenic E. coli were 19.56%, 6.52%, 10.86% respectively. Mixed infection was diagnosed in 30.43% of herds, and L. intracellularis and Salmonella enterica serotype Typhimurium are main pathogens association (10.87%). B. pilosicoli was diagnosed only in two herds, always associated with mixed infections. B. hyodysenteriae and T. suis were not demonstrated in any sample. These pathogens have been reported world-wide but studies regarding epidemiology in Brazil are few. This study contributes to establish of prevention programs for the control enteropathogens in grower finish herds in Brazil.

Colonisation and shedding of Lawsonia intracellularis in experimentally inoculated rodents and in wild rodents on pig farms

Lawsonia intracellularis is an intracellular bacterium causing proliferative enteropathy in various animal species, and is considered an economically important pathogen of pigs. Rats and mice have been implicated as external vectors for a wide range of pig pathogens, including L. intracellularis. Previous studies have demonstrated L. intracellularis infection and proliferative enteropathy in rodents, but did not show the duration of shedding or the number of L. intracellularis shed by infected rodents, and therefore the infection risk that rodents pose to pigs. In this study, the number of L. intracellularis shed in the faeces and intestinal mucosa of wild rats trapped on pig farms was determined by a quantitative real time polymerase chain reaction assay. The prevalence of L. intracellularis in wild rats trapped on pig farms with endemic proliferative enteropathy (PE) was very high (≥ 70.6%), and large numbers of L. intracellularis were shed (10(10)/g of faeces) in a small proportion of wild rats. The duration of colonisation in laboratory rats and mice challenged with porcine isolates of L. intracellularis was also shown. Faecal shedding of L. intracellularis persisted for 14-21 days in rats and mice that were mildly affected with histological lesions of PE. The humoral immune response to L. intracellularis persisted for 40 days in both species. This study demonstrates that rodents may be an important reservoir of L. intracellularis on piggeries, and hence rodent control is important in disease eradication programs on pig farms.

Diagnostic performance of different fecal Lawsonia intracellularis-specific polymerase chain reaction assays as diagnostic tests for proliferative enteropathy in pigs: a review

Traditionally, diagnosis of Lawsonia intracellularis-associated proliferative enteropathy (PE) has depended on necropsy and histology. Since the establishment of the etiologic role of L. intracellularis, a number of specific polymerase chain reaction (PCR) assays have been developed for the detection of DNA in feces. The present article is a systematic review of peer-reviewed publications on the application of L. intracellularis-specific fecal PCR as an antemortem diagnostic test for histologic lesions of PE in pigs. Based on this information, a range of diagnostic sensitivities (36-100%) and specificities (50-100%) of the published tests was calculated. Validity and confidence limits of the estimates varied considerably. The positive and negative predictive values of 6 different PCR assays were calculated for PE prevalence of 15%, 30%, 45%, 60%, 75%, and 90%, using a histologic case definition of PE and based on the reported test sensitivities and specificities. The simulated predictive values suggested that applying the fecal PCR assay as a diagnostic test is more likely to overestimate than underestimate the number of pigs having histologic lesions of PE under field conditions.

Re-challenge of pigs following recovery from proliferative enteropathy

An experimental challenge model was developed to demonstrate Lawsonia intracellularis colonization and reproduction of proliferative enteropathy (PE) in naïve weaner pigs. Groups of pigs were orally dosed with between 10(10) and 10(5)L. intracellularis extracted from haemorrhagic PE affected mucosa. Pigs were monitored for clinical signs and intestinal lesions of PE and evidence of bacterial colonization by serology and faecal polymerase chain reaction (PCR). One group of challenged pigs were necropsied after 21 days to confirm the reproduction of PE. L. intracellularis colonization and seroconversion was delayed in pigs dosed with lower numbers of L. intracellularis. When faecal shedding of L. intracellularis ceased to be detected in all of the challenged pigs, they were re-dosed orally with approximately 10(10)L. intracellularis and monitored for evidence of re-colonization and clinical disease. This study demonstrated that pigs previously challenged with L. intracellularis were protected from re-colonization and clinical disease on subsequent exposure 10 weeks later, regardless of the initial dose of L. intracellularis.

Human inflammatory bowel disease does not associate with Lawsonia intracellularis infection

BACKGROUND

There is increasing evidence that bacterial infection of the intestinal mucosa may contribute to the pathogenesis of inflammatory bowel diseases (IBD). In pigs, an obligate intracellular bacterium, Lawsonia intracellularis (LI), was shown to cause proliferative enteropathy (PE) of which some forms display histological and clinical similarities to human IBD. Since LI-similar Desulfovibrio spp. may infect human cells, we hypothesized that LI might be associated with the development of human IBD.

RESULTS

In human intestinal tissue samples, PCR using LLG, 50SL27, LSA and strictly LI-specific 16SII primers, yielded either no amplicons or products with weak homology to human genomic sequences. Sequencing of these amplicons revealed no specificity for LI. However, amplification of DNA with less specific 16SI primers resulted in products bearing homology to certain Streptococcus species. These 16SI-amplified products were present in healthy and diseased specimens, without obvious prevalence.

CONCLUSION

LI is not associated with the pathogenesis of UC or CD. Whether an immunologic response to commensal bacteria such as streptococci may contribute to the chronic inflammatory condition in IBD, remained to be determined.

Development of a two-step nested duplex PCR assay for the rapid detection of Brachyspira pilosicoli and Brachyspira intermedia in chicken faeces

Avian intestinal spirochaetosis (AIS) is an infection of the caeca and/or colo-rectum of laying and meat breeder hens caused by anaerobic intestinal spirochaetes of the genus Brachyspira. AIS can result in a variety of symptoms, including delayed and/or reduced egg production, and increased faecal water content. The two most commonly reported Brachyspira species involved in AIS are Brachyspira pilosicoli and Brachyspira intermedia, and their detection and identification can be difficult and time consuming. In the current study a two-step nested duplex PCR (2S-N-D-PCR) was developed for the detection of these two species, using DNA extracted from washed chicken faeces. In the first step, a duplex PCR (D-PCR) amplifying Brachyspira genus-specific portions of the 16S rRNA and NADH oxidase (nox) genes was undertaken on the washed faeces. In the second step, a nested D-PCR was used that amplified species-specific portions of the 16S rRNA gene of B. pilosicoli and the nox gene of B. intermedia from the amplicons produced in the first step. The 2S-N-D-PCR was rapid and specific, and could be used to detect approximately 10(3) cells of each spirochaete species per gram of washed faeces. When tested on 882 chicken faecal samples from infected flocks, it detected 4-5% more positive faecal samples than did the standard method of selective anaerobic culture followed by individual species-specific PCR assays conducted on the growth on the primary plate. The application of this new technique should improve diagnostic capacity, and facilitate further studies on AIS.