Influence of diet on the experimental infection of pigs with Brachyspira pilosicoli

Vaccination of chickens with the 34 kDa carboxy-terminus of Bpmp72 reduces colonization with Brachyspira pilosicoli following experimental infection

The anaerobic intestinal spirochaete Brachyspira pilosicoli colonizes the large intestine of a variety of species of mammals and birds, and may result in colitis, diarrhoea and reductions in growth rate. Naturally occurring infections in chickens are largely confined to adult laying and breeding birds. In this study, the 34 kD carboxy-terminus of the prominent outer membrane protein Bmp72 of B. pilosicoli was expressed as a histidine-tagged recombinant protein and used to immunize two groups (B and C) of 15 individually housed layer chickens. Vaccination was with either 100 μg (B) or 1 mg (C) protein emulsified with Freund's incomplete adjuvant delivered into the pectoral muscles, followed three weeks later by 1 mg of protein in phosphate buffered saline delivered via crop tube. Two weeks later these and 15 non-vaccinated positive control birds (group A) housed in the same room were challenged via crop tube with B. pilosicoli avian strain CPS1. B. pilosicoli was detected in the faeces of all control birds and in 14 of the vaccinated birds in each vaccinated group at some point over the 30-day period following challenge. Colonization was delayed and the duration of excretion was significantly reduced (P = 0.0001) in both groups of vaccinated birds compared to the non-vaccinated control birds. Fewer immunized birds had abnormal caecal contents at post mortem examination compared to non-vaccinated birds, but the difference was not statistically significant. This study indicates that recombinant Bmp72 C-terminus has potential to be developed for use as a vaccine component to provide protection against B. pilosicoli infections. RESEARCH HIGHLIGHTS Laying chickens were immunized with recombinant Brachyspira pilosicoli membrane protein Bpmp72. Immunized birds had a highly significant reduction in the duration of colonization. Fewer immunized than control birds had abnormal caecal contents after infection. Bpmp72 showed potential for use as a novel vaccine component for B. pilosicoli.

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.

Biology and Diseases of Swine

Swine are used in biomedical research as models for biomedical research and for teaching. This chapter covers normative biology and behavior along with common and emerging swine diseases. Xenotransplantation is discussed along with similarities and differences of swine immunology.

Brachyspira murdochii Colitis in Pigs

The weakly beta-hemolytic porcine spirochete Brachyspira murdochii is considered a normal intestinal commensal. In the present study, however, a field case of B murdochii–associated catarrhal colitis was identified in a pig, as characterized by extensive spirochetal colonization of the surface epithelium. Experimentally, 8 weaned pigs were challenged with the B murdochii isolate, reproducing catarrhal colitis in 2 animals. By applying fluorescent in situ hybridization using a species-specific oligonucleotide probe targeting 23S rRNA, B murdochii organisms were found in high numbers and were closely associated with the surface epithelium in the pigs with catarrhal colitis. The results indicate that, when present in high numbers, B murdochii is low pathogenic for pigs.

Attraction of Brachyspira pilosicoli to mucin

The anaerobic intestinal spirochaete Brachyspira pilosicoli colonizes the large intestine of various species, including humans. In the colon this spirochaete can penetrate the overlying mucus layer, attach by one cell end to the underlying enterocytes, and initiate localized colitis and diarrhoea. The aim of this study was to investigate whether, as part of the colonization process, B. pilosicoli is attracted to mucin. Fifteen B. pilosicoli strains isolated from humans, pigs, chickens and dogs, and a control strain of Brachyspira hyodysenteriae, were analysed for their ability to enter solutions of hog gastric mucin in an in vitro capillary tube assay. No significant attraction was detected with 1 % mucin, but some strains started to enter a 2 % solution, and attraction then increased with increasing concentrations to peak at around 6-8 % mucin. A similar increase was seen with B. hyodysenteriae, although this activity peaked at 6 % mucin and then declined, suggesting that the two species have different affinities for mucin. These mucin concentrations were much higher than those used in previous experimental studies with Brachyspira species. The viscosities of the 6-8 % mucin solutions were around 7-12 mPa s, which were similar to the measured viscosities of the mucus layer overlying the epithelium in the caecum and colon of experimental pigs. The strains varied in their motility, as assessed by their ability to enter tubes containing chemotaxis buffer, but there was no significant relationship between this motility and the extent of their ability to enter the mucin solutions. Different strains also had different propensities to enter the mucin solutions, but there were no consistent differences according to the host species of origin. B. pilosicoli strain 95/1000 was attracted towards a solution of d-serine, suggesting that chemotaxis was involved in the attraction to mucin; however, 95/1000 was also attracted to viscous solutions of polyvinylpyrrolidone (PVP), in a manner mirroring the response to mucin, and hence suggesting the involvement of viscotaxis in the attraction to mucin. B. hyodysenteriae B204 showed a similar viscotaxis to PVP. Further studies are required to determine whether the in vitro interaction of a given strain with mucin is a useful indicator of its in vivo colonization ability, and hence could be used as a potential marker for virulence.

Colonic spirochetosis in animals and humans

Colonic spirochetosis is a disease caused by the gram-negative bacteria Brachyspira aalborgi and Brachyspira pilosicoli. B. pilosicoli induces disease in both humans and animals, whereas B. aalborgi affects only humans and higher primates. Symptoms in humans include diarrhea, rectal bleeding, and abdominal cramps. Colonic spirochetosis is common in third world countries; however, in developed countries, the disease is observed mainly in homosexual males. Terminally ill patients infected with Brachyspira are particularly at risk for developing spirochetemia. Diarrhea, poor growth performance, and decreased feed-to-gain efficiency is seen in pigs with colonic spirochetosis. The disease in chickens is characterized by delayed and/or reduced egg production, diarrhea, poor feed conversion, and retarded growth. Thus, colonic spirochetosis can represent a serious economic loss in the swine and poultry industries. The organisms are transmitted by the fecal-oral route, and several studies have demonstrated that human, primate, pig, dog, or bird strains of B. pilosicoli can be transmitted to pigs, chickens, and mice. B. pilosicoli may be a zoonotic pathogen, and although it has not been demonstrated, there is a possibility that both B. pilosicoli and B. aalborgi can be transferred to humans via contact with the feces of infected animals, meat from infected animals, or food contaminated by food handlers. Neither B. pilosicoli nor B. aalborgi has been well characterized in terms of basic cellular functions, pathogenicity, or genetics. Studies are needed to more thoroughly understand these Brachyspira species and their disease mechanisms.