Antigenic analysis of Campylobacter species and an intracellular Campylobacter-like organism associated with porcine proliferative enteropathies

Preparation and Characterization of Polyclonal and Monoclonal Antibodies against Lawsonia Intracellularis

Proliferative enteropathy is an intestinal infectious disease caused by the obligate intracellular bacterium Lawsonia intracellularis. Immunohistochemistry staining has superior sensitivity over hematoxylin and eosin and silver staining for detecting L. intracellularis in histological sections. A L. intracellularis—specific monoclonal antibody (MAb) produced in the UK (IG4 MAb) has been described in the literature. However, no monoclonal or polyclonal antibodies are commercially available. Therefore, the objective of this study was to produce and characterize new polyclonal and monoclonal antibodies against L. intracellularis that are suitable for diagnostic use. The new monoclonal (2001 MAb) and polyclonal antibodies (1999 PAb) were compared with the IG4 MAb using Western blot analysis of outer membrane proteins (OMPs) of 6 L. intracellularis isolates, Bilophila wadsworthia and Brachyspira hyodysenteriae and using immunohistochemistry of known positive and negative histologic samples and pure cultures of L. intracellularis, B. wadsworthia, B. hyodysenteriae, Salmonella choleraesuis, S. typhimurium, and Escherichia coli K88. Immunogold staining using 2001 MAb was performed to show the specificity of the antibody against an L. intracellularis surface protein. Western blot analysis showed that the 2001 MAb targeted an OMP of 77 kD, which made it different from the IG4 MAb that targeted an 18-kD OMP. The immunogold stain demonstrated the specificity of the 2001 MAb to a surface protein of L. intracellularis. The polyclonal antibody (1999 PAb) targeted 5 OMPs (77, 69, 54, 42, and 36 kD). Both the 2001 MAb and 1999 PAb stained known positive, but not negative, histologic samples. Both the 2001 MAb and 1999 PAb reacted with a pure culture of L. intracellularis but not with any other common enteric pathogens. These two new antibodies will be useful for immunodiagnosis of L. intracellularis.

Porcine proliferative enteropathy: an important disease with questions remaining to be solved

Proliferative enteropathy caused by the intracellular bacterium Lawsonia intracellularis is an endemic disease with high herd prevalences reported worldwide. The infection has a considerable impact on pig production and herd economics and, with the development of new diagnostic techniques, L. intracellularis is being identified in an increasing number of pig herds and a wider range of species. This paper reviews current knowledge of the disease, with a focus on the epidemiology in pigs. The prevalence of infection, transmission, predisposing factors, microbial features, pathogenesis, clinical signs, diagnosis, treatment and control are discussed. The disease is mainly controlled by antibiotic treatment and vaccination at herd level. In the development of effective measures to prevent the spread of the infection, increased knowledge of the transmission and persistence of the microorganism are crucial.

Differential infection efficiencies of peripheral lung and tracheal tissues in sheep infected with Visna/maedi virus via the respiratory tract

The main routes of transmission of Visna/maedi virus (VMV), an ovine lentivirus, are thought to be through ingestion of infected colostrum and/or milk or through inhalation of respiratory secretions. Whereas oral transmission appears to be mediated via epithelial cells within the small intestine, the mechanism of virus uptake in the respiratory tract is unknown. In addition, it is not known whether infection is mediated by cell-associated or cell-free VMV, previous studies having not addressed this question. Intratracheal (i.t.) injection of VMV is known to be a highly efficient method of experimental infection, requiring as little as 101 TCID50 VMV for successful infection. However, using a tracheal organ culture system, we show here that ovine tracheal mucosa is relatively resistant to VMV, with detectable infection only seen after incubation with high titres of virus (⩾105 TCID50 ml−1). We also demonstrate that i.t. injection results in exposure of both trachea and the lower lung and that the time taken for viraemia and seroconversion to occur after lower lung instillation of VMV was significantly shorter than that observed for tracheal instillation of an identical titre of virus (P=0.030). This indicates that lower lung and not the trachea is a highly efficient site for VMV entry in vivo. Furthermore, cell-free virus was identified within the lung-lining fluid of naturally infected sheep for the first time. Together, these results suggest that respiratory transmission of VMV is mediated by inhalation of aerosols containing free VMV, with subsequent virus uptake in the lower lung.

Development, characterization and diagnostic application of a monoclonal antibody specific for a proteinase K resistant Lawsonia intracellularis antigen

Proliferative enteropathy (PE) is one of the most important infections in pigs caused by Lawsonia intracellularis, an obligate intracellular bacterium. The purpose of the present investigation was to develop monoclonal antibodies with specificity to L. intracellularis useful both for diagnostic purposes (by immunohistochemistry) and for bacterial characterization. Several antibody producing hybridomas were established by fusion of mouse myeloma with spleen cells from BALB/c mice immunized with mucosa scrapings of the intestinal mucosa from a L. intracellularis infected pig. A monoclonal antibody (mAb), Law1-DK, isotyped as IgG2b was selected by indirect immunofluorescence antibody test (IFAT). Histological sections of the intestines from pigs affected by proliferative enteropathy and in vitro grown bacteria in cell culture were tested positive for the presence of L. intracellularis with the mAb. A molecule at 21 kDa was recognized by the mAb in a Western blotting analysis when a whole-cell preparation of L. intracellularis was run on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This antigen was released from L. intracellularis by mild heat treatment and was resistant to proteinase K digestion, suggesting it to be non-protein, e.g., lipopolysaccharide (LPS). This suggestion was supported by its presence in the aqueous phase of a phenol-water extract. The inhibitory effect of periodate oxidation on the antigen-antibody binding confirmed the participation of a carbohydrate epitope. The new mAb was tested highly specific for L. intracellularis by applying in situ hybridization with a L. intracellularis specific probe targeting 16S ribosomal RNA simultaneously with the IFAT.

Evaluation of protective immunity in pigs following oral administration of an avirulent live vaccine of Lawsonia intracellularis

OBJECTIVE

To evaluate the efficacy of an orally administered avirulent live vaccine to protect pigs against challenge exposure with virulent Lawsonia intracellularis.

ANIMALS

108 weaned 3-week-old pigs (35 in experiment 1 and 73 in experiment 2).

PROCEDURE

2 experiments were conducted. On day 0, vaccinates were orally administered vaccine via drench or in drinking water, whereas challenge-control pigs were administered cultured medium. On day 21, pigs were challenge exposed with a virulent heterologous isolate of L. intracellularis. Clinical observations, weights, seroconversion, and fecal excretion of L. intracellularis were measured until day 42. At study termination, pigs were euthanatized and examined for L. intracellularis-specific lesion development of the ileum and colon.

RESULTS

Pigs receiving a single dose of vaccine were protected when challenge exposed with virulent L. intracellularis (at least 10(77) TCID50/dose). In experiment 1, vaccinates had significantly less fecal excretion (47% and 40% for days 35 and 42, respectively), compared with challenge-control pigs. In experiment 2, vaccinates had significantly less fecal excretion (50% and 58% for days 35 and 42, respectively), compared with challenge-control pigs. Significant reductions in lesion development were evident in the ileum of vaccinated pigs (70% and 56% at day 42 for experiments 1 and 2, respectively), compared with challenge-control pigs.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration by drench or via drinking water of an avirulent live vaccine against L. intracellularis resulted in substantial protection against proliferative enteropathy among vaccinates and offers a better way to reduce stress of pigs during vaccine administration.

Survey of Porcine Proliferative Enteritis in the Tohoku District of Japan

A survey of proliferative enteritis (PE) in pigs at a meat processing plant was conducted using polymerase chain reaction (PCR) testing methods. During the investigation period, 227 of 83,717 pigs brought to the meat processing plant from Iwate, Fukushima, Miyagi, Niigata, and Yamagata Prefectures displayed characteristic general pathological features in terminal ileum, including mucosal hypertrophy and reticulation of serosal surface. Of these, 179 cases were further examined in the laboratory. All cases displayed characteristic histopathological features, and the specific band of the Lawsonia intracellularis (Li) causative agent of PE in pigs was detected in 155 cases by PCR testing methods. These results suggested a general infiltration of Li in the Tohoku district.

LsaA, an antigen involved in cell attachment and invasion, is expressed by Lawsonia intracellularis during infection in vitro and in vivo

Lawsonia intracellularis has been identified recently as the etiological agent of proliferative enteropathies, which are characterized by intestinal epithelial hyperplasia and associated moderate immune responses. This disease complex has been reported in a broad range of animals, prevalently in pigs, and L. intracellularis has been linked with ulcerative colitis in humans. L. intracellularis is an obligate intracellular bacterium, and the pathogenic mechanisms used to cause disease are unknown. Using in vitro-grown organisms as a source of genomic DNA, we identified a Lawsonia gene which encodes a surface antigen, LsaA (for Lawsonia surface antigen), associated with attachment to and entry into cells. The deduced amino acid sequence of this protein showed some similarity to members of a novel protein family identified in a number of other bacterial pathogens but for which roles are not fully defined. Transcription of this gene was detected by reverse transcription-PCR in L. intracellularis grown in vitro in IEC18 cells and in bacteria present in ileal tissue from infected animals. Immunohistochemistry with specific monoclonal antibody and immunoblotting with sera from infected animals demonstrated that LsaA protein is synthesized by L. intracellularis during infection. Expression of this gene during infection in vitro and in vivo suggests that this surface antigen is involved during infection, and phenotypic analysis indicated a role during L. intracellularis attachment to and entry into intestinal epithelial cells

Comparison of different methods for diagnosis of porcine proliferative enteropathy

The objectives of this study were: (1) to compare 2 methods of serology; (2) to compare 3 histologic techniques; and (3) to compare 2 methods of detecting shedding in pigs experimentally challenged with Lawsonia intracellularis. The sensitivities of these tests were determined by the detection of infection. Forty 5-week-old pigs were inoculated on day 0 with intestinal homogenate from pigs with proliferative enteropathy (PE). Clinical evaluation was done on day 7 and daily from day 14 to 28 postinoculation. Fecal shedding of L. intracellularis was monitored by use of polymerase chain reaction (PCR) analysis and immunoperoxidase staining at 7-day intervals. Serum was obtained on days 0 and 28 for serologic testing by glass slide and tissue culture indirect fluorescent antibody tests. At euthanasia on day 28, gross intestinal lesions were evaluated and ileum samples collected for histologic analyses. Ileal histologic sections from each animal were stained by hematoxylin and eosin, Warthin-Starry silver stain, and immunohistochemistry (IHC). Of the 40 pigs, 36 had gross lesions typical of PE at necropsy. The percentage of agreement between the 2 serologic methods was 94.4%. Immunoperoxidase stain of fecal smears was more sensitive than PCR for detecting fecal shedding, especially on day 21 (89.5% and 60.5%, respectively) and day 28 (59.4% and 37.5%, respectively) post-inoculation. The IHC stain was much more sensitive for detecting infection than the routinely used hematoxylin and eosin and Warthin-Starry silver stains. In conclusion, in experimentally infected pigs, both serologic methods were appropriate techniques for detecting infection. For fecal samples, PCR has low sensitivity. Immunohistochemistry is the best diagnostic tool for formalin-fixed samples.

Hepatobiliary inflammation, neoplasia, and argyrophilic bacteria in a ferret colony

Hepatobiliary disease was diagnosed in eight of 34 genetically unrelated cohabitating pet ferrets (Mustela putorios furo) during a 7-year period. The eight ferrets ranged in age from 5 to 8 years and exhibited chronic cholangiohepatitis coupled with cellular proliferation ranging from hyperplasia to frank neoplasia. Spiral-shaped argyrophilic bacteria were demonstrated in livers of three ferrets, including two with carcinoma. Sequence analysis of a 400-base pair polymerase chain reaction product amplified from DNA derived from fecal bacteria from one ferret demonstrated 98% and 97% similarity to Helicobacter cholecystus and Helicobacter sp. strain 266-1 , respectively. The clustering of severe hepatic disease in these cohabitating ferroes suggests a possible infectious etiology. The role of Helicobacter species and other bacteria in hepatitis and/or neoplasia in ferrets requires further study.

Immunohistochemistry and polymerase chain reaction for the detection of Lawsonia intracellularis in porcine intestinal tissues with proliferative enteropathy

Detection method of Lawsonia intracellularis was studied in formalin-fixed paraffin-embedded intestinal tissues from 5 naturally infected pigs by immunohistochemistry with a monoclonal antibody against outer membrane protein of L. intracellularis. Warthin-Starry silver stain revealed clusters of argyrophilic, slightly curved rod-shaped organisms in the apical cytoplasm of enterocytes. Immunohistochemical staining with a L. intracellularis-specific monoclonal antibody confirmed the presence of the organism in the apical cytoplasm of hyperplastic enterocytes. The presence of L. intracellularis in the ileum of pig with proliferative enteropathy was confirmed by polymerase chain reaction (PCR) further on the basis of amplification of 319 base pair products specific for porcine L. intracellularis chromosomal DNA. Immunohistochemistry and PCR may be a complementary method to confirm the diagnosis of L. intracellularis infection in pigs.

In-vitro interactions of Lawsonia intracellularis with cultured enterocytes

Strains of the obligately intracellular bacterium Lawsonia intracellularis, the etiologic agent of porcine proliferative enteropathy, were co-cultured in rat enterocyte cell cultures (IEC-18) and examined ultrastructurally. No regular surface arrays typical of surface or S-layers were visible on any bacterial strain, with or without Triton-X-100 detergent treatment. In separate experiments, there was no difference in the ability of L. intracellularis to attach and enter enterocytes with or without the presence of added bovine plasma fibronectin, or the peptide Arg-Gly-Ser. Interestingly, there was an increase in the invasiveness of L. intracellularis in the presence of the peptide Arg-Gly-Asp (RGD), in a dose-related manner. A reduction was observed in the ability of L. intracellularis to invade enterocytes in the presence of monovalent fragments of IgG monoclonal antibodies to an outer surface component of L. intracellularis. This neutralization showed an antibody concentration-dependent titration effect and was not apparent with co-cultures incorporating control antibodies. The exact nature of ligand and cell receptor interactions for L. intracellularis remain to be determined.

Intracellular Campylobacter-like organisms associated with rectal prolapse and proliferative enteroproctitis in emus (Dromaius novaehollandiae)

Rectal prolapse was the presenting clinical finding in a group of juvenile emus (Dromaius novaehollandiae). Gross findings included severely thickened and rugose distal rectal mucosae. Histologically, there were thickened villi, enterocyte hyperplasia, dilated glands filled with mucus and heterophils, and a dense infiltrate of heterophils, macrophages, lymphocytes, and plasma cells in the lamina propria. Examination of Warthin-Starry silver-stained sections revealed numerous apically located comma-shaped intracytoplasmic bacteria approximately 1 x 3 microns in size. Campylobacter-like organisms morphologically compatible with ileal symbiont intracellularis now known as Lawsonia intracellularis were seen via electron microscopy. Bacteria were further characterized by indirect immunofluorescence using monoclonal antibody specific for the 25-27-kd outer membrane protein of L. intracellularis.

Development of persistent intestinal infection and excretion of Lawsonia intracellularis by piglets

Challenge experiments using Lawsonia intracellularis as oral inocula have established its aetiological role in porcine proliferative enteropathy. Thirty piglets, in four groups, were weaned at 21 days of age and inoculated orally at 24 days. Six piglets were challenged with 1.0 x 10(8) L intracellularis strain 916/91 (NCTC 12657) passaged 12 times in vitro, six with 5.0 x 10(8) of the same strain, seven with 3.0 x 10(8) L intracellularis strain LR 189/5/83, passaged nine times, and 11 controls were dosed with sucrose-potassium glutamate buffer. An immunofluorescence assay for L intracellularis was applied to faecal smears and a polymerase chain reaction (PCR) incorporating L intracellularis-specific primers was applied to extracts of bacterial DNA derived from the faeces samples. Up to five pigs in each challenge group excreted detectable L intracellularis in faeces, in samples taken between two and 10 weeks after challenge. Some of the pigs had up to 7 x 10(8) L intracellularis g-1 faeces. The average weight gains of the higher dose challenge groups were moderately below those of the control pigs between three and nine weeks after challenge; diarrhoea was also observed in six pigs, two to four weeks after challenge. Numerous L intracellularis were detected in the intestines of all the pigs challenged with strain LR 189/5/83 and two of the pigs challenged with 916/91, but not in other tissues.

Replication of Australian porcine isolates of Ileal symbiont intracellularis in tissue culture

Ileal symbiont intracellularis (ISI) isolated from Australian cases of PIA and PHE was replicated in the rat ileum enterocyte cell line IEC 18. The number of ISI within cells varied, as did the number of ISI infected within the monolayer. At 24 h post infection a large number of cells were infected with approximately 100 ISI per cell. At the termination of infection, fewer IEC 18 cells were infected but ISI had replicated to fill the cell cytoplasmic space. Numerous foci of infected cells were visible in the monolayer, containing as many as 15 densely infected cells. Division of ISI infected cells indicated the transmission of ISI in the cytoplasm to daughter cells. This suggests that the replication of ISI in culture appears to be reasonably cell dependent. No cytopathic effects were observed in the infected cultures.

Specific in situ hybridization of the intracellular organism of porcine proliferative enteropathy

The identity of the intracellular bacteria found in the enterocytes of pigs with proliferative enteropathy was investigated using specific DNA probes to various Campylobacter species and to a novel organism, ileal symbiont intracellularis. The ilea from pigs (Nos. 1-7) that were diagnosed by routine histopathology as having proliferative enteropathy were used. Diagnosis was made on the basis of proliferation of the enterocytes on hematoxylin and eosin-stained sections and the presence of large numbers of intracellular curved organisms on Warthin-Starry silver-stained sections. Four of these pigs (Nos. 1-4) had the chronic form of the disease, porcine intestinal adenomatosis, and three (Nos. 5-7) had the acute form, proliferative hemorrhagic enteropathy. An additional three normal pigs (Nos. 8-10) were obtained from three separate farms with no history of proliferative enteropathy. Frozen ileal sections were examined by in situ hybridization with DNA probes specific for ileal symbiont intracellularis and the three porcine intestinal Campylobacter species, C. coli, C. hyointestinalis, and C. mucosalis. In all seven pigs with either the intestinal adenomatosis or hemorrhagic enteropathy form of the disease, a DNA probe specific for ileal symbiont intracellularis hybridized to localized foci in the apical cytoplasm of ileal enterocytes. These hybridization sites corresponded to the location of intracellular bacteria in silver-stained sections of adjacent tissue. Sections from the three normal pigs tested with this probe and from all pigs tested with the Campylobacter species-specific DNA probes showed no specific hybridization reactions. The identity of the intracellular organism in these diseased pigs is ileal symbiont intracellularis.

Relationship between Ileal symbiont intracellularis and porcine proliferative enteritis

The relationship between Ileal symbiont (IS) intracellularis, formerly known as a Campylobacter-like organism, and porcine proliferative enteritis (PE) was studied by use of pigs with experimentally transmitted PE. Twenty one pigs were experimentally inoculated with homogenized ileal mucosa from a pig that died with PE, and 7 were maintained as uninoculated controls. Fecal samples were collected, and pigs were necropsied weekly postinoculation. Light microscopy and electron microscopy were used to examine tissues for lesions of PE and infectious agents. DNA was extracted from the fecal samples and assayed for the presence of sequences specific for IS intracellularis by dot blot hybridization and polymerase chain reaction amplification. IS intracellularis was detected by the polymerase chain reaction in the feces of 20 of 21 inoculated pigs but not in the feces of uninoculated pigs. Seven inoculated pigs but no uninoculated pigs were detected shedding IS intracellularis by dot blot hybridization. Shedding was detected 1 to 5 weeks after inoculation, and clinical signs were seen in the second to fifth weeks after inoculation. Few pigs without lesions of PE were found to shed IS intracellularis. There was a highly significant association between the presence of IS intracellularis in feces or tissue and the presence of microscopic proliferative lesions and between the severity of the lesions of PE and the percentage of IS intracellularis-infected intestinal crypts. Pigs that ceased shedding IS intracellularis were significantly less likely to have proliferative lesions. These and previous reports are consistent with the hypothesis that IS intracellularis is a necessary causative agent of PE.

Intracellular bacteria of porcine proliferative enteropathy: cultivation and maintenance in vitro

An obligate intracellular bacterium was isolated from the intestines of all 10 cases of porcine proliferative enteropathy from four different pig farms. The organism grew in a rat enterocyte cell line (IEC-18) and was maintained over 20 passages. The growth of the bacteria was assessed by immunostaining of cells exposed to infection. Infection was not associated with morphological cell change, and growth was confined to cells infected at the time of each transfer of infection and the progeny of these cells. The bacterium is a microaerophilic, cell dependent, curved or rod-shaped, gram-negative bacillus that multiplies freely in the enterocyte cytoplasm. Cell cultures containing the intracellular bacteria appear to be free of other microorganisms, including chlamydiae and viruses.

Production of a monoclonal antibody that recognizes the lipopolysaccharide of a Campylobacter-like organism

A monoclonal antibody was produced to a Campylobacter-like organism (RMIT 32A) which was isolated from the terminal ileum of a pig with proliferative enteritis. Isotyping of the antibody revealed that it was an IgG2a with kappa light chains. Immunoblots using the antibody against proteinase-K-treated whole cell lysates of RMIT 32A, a selection of Campylobacter species and other enteric bacteria showed that the antibody was specific for RMIT 32A and was directed against the lipopolysaccharide. This antibody can be used for the specific detection of RMIT 32A.

Experimental reproduction of porcine proliferative enteritis

A campylobacter-like bacterium, isolated from the terminal ileum of a pig with porcine proliferative enteritis (PPE), was used to initiate PPE in healthy crossbred pigs. Post-mortem examinations of pigs infected orally with the bacterium revealed thickening of the terminal ileum, haemorrhage within the ileum, degeneration of ileal villi and large quantities of bile and mucous in the ileal contents. Histopathological examination revealed that the terminal ileum, ileo-caecal valve and caecum from infected pigs had partial or total loss of mucous membrane, hyperplasia of the crypt and glandular epithelial cells, campylobacter-like organisms in and around the Peyers' patches and lymphoid aggregates in the mucosa. The causative organism was re-isolated from the intestinal specimens of infected animals post-mortem. In control animals, kept under the same conditions, no evidence of abnormality was observed in the terminal ileum, ileo-caecal valve or caecum.

Isolation of an intracellular bacterium from hamsters (Mesocricetus auratus) with proliferative ileitis and reproduction of the disease with a pure culture

An intracellular bacterium was isolated from hamsters (Mesocricetus auratus) with proliferative ileitis. The organism was isolated in Intestine 407 and GPC-16 cell cultures (incubated in a microaerophilic atmosphere) from isolated and lysed epithelial cells from hamsters with proliferative ileitis. The bacterium measured 1.4 to 1.7 microns in length by 0.26 to 0.34 microns in width, was slightly curved, and had an irregular trilaminar cell wall. Inoculation of hamsters with a cell culture lysate containing the organism or a 0.65-microns-pore-size filtrate of an infected-cell lysate resulted in the typical lesions of proliferative ileitis in approximately 50% of the animals in 28 days. Hamsters inoculated with uninfected cells or a 0.2-microns-pore-size filtrate of an infected-cell lysate remained uninfected. Attempts to propagate the organism on cell-free media have been unsuccessful.

Cloned DNA probes specific for the intracellular Campylobacter-like organism of porcine proliferative enteritis

Although the etiology of porcine proliferative enteritis is not understood, the consistent presence of intracellular Campylobacter-like organisms (CLOs) in proliferating pig intestinal epithelial cells suggests that the organism is involved in the disease process. In order to obtain information about this organism, we generated and characterized specific DNA probes to the intracellular CLO which was purified without culturing. Intracellular CLOs were isolated from mucosa by homogenization, filtration, and absorption to wheat germ agglutinin-Sepharose. The DNA was purified, and a CLO genomic library was constructed. The specificity of recombinant plasmids was confirmed by both dot blot hybridization and Southern analysis of normal and diseased mucosa, as well as of a variety of Campylobacter species. Several of the CLO-specific probes hybridized with porcine mucosa obtained from pigs with proliferative enteritis but not with nondiseased mucosa. The probes hybridized equally with mucosa or DNA obtained from each of the two clinical forms of proliferative enteritis, i.e., proliferative hemorrhagic enteropathy and porcine intestinal adenomatosis. The CLO-specific probes failed to hybridize with any of the commonly isolated porcine Campylobacter species, including Campylobacter hyointestinalis, C. mucosalis, and C. coli. Therefore, the intracellular CLO of porcine proliferative enteritis may be an as yet unidentified or uncultured species.

Southern blot analysis of strain variation in Campylobacter mucosalis

A panel of three DNA probes were derived at random from a genomic DNA library of Campylobacter mucosalis strain E8384-4. Each probe hybridized specifically to C. mucosalis DNA from bacteria fixed to nylon membranes. The probes did not hybridize to DNA from other Campylobacter species or to other bacteria even at 100-fold higher amounts. Each probe hybridized to all of 24 isolates of C. mucosalis which had been collected over time from different geographic locations. Southern blot analysis of selected C. mucosalis isolates was carried out to determine if the probes would be useful for differentiating among various isolates. It indicated that restriction fragment length polymorphisms (RFLPs) exist at the loci identified by our probes. These differences were used to characterize seven C. mucosalis isolates recovered from pigs in Minnesota. The results suggest that RFLP analysis may be a useful tool for epidemiological studies of C. mucosalis.

Enterocecocolitis associated with intraepithelial Campylobacter-like bacteria in rabbits (Oryctolagus cuniculus)

We examined 28 suckling, weanling, and young adult rabbits with lethargy, inappetence, and mucinous, semifluid feces. Sixteen of the rabbits had intestinal lesions. In eight of these rabbits, the primary changes were multifocal to diffuse epithelial proliferation and accumulation of lymphocytes, macrophages, or both in the lamina propria of the small intestine, cecum, and sacculated colon. In two of these rabbits, the accumulation of macrophages in the lamina propria was extensive. The other eight rabbits had erosive and suppurative cecocolitis, and four of the rabbits with proliferative lesions also had suppurative cecocolitis. In Warthin-Starry-stained sections of affected intestine, curved or spiral bacteria were visible within degenerated or hyperplastic epithelium, in luminal exudate, or in both. Such organisms were sparse or not found in the other 12 rabbits, which did not have intestinal lesions. The bacteria ultrastructurally resembled intraepithelial Campylobacter-like bacteria previously observed in proliferative enteritis in a variety of species and in acute typhlitis in young rabbits. In immunofluorescence tests, Campylobacter-like bacteria in epithelial cells, crypt lumina, and in luminal exudates in both proliferative and erosive lesions bound monoclonal antibodies and polyclonal antisera prepared against intracellular bacteria found in proliferative enteritis in pigs, hamsters, and ferrets. These observations indicate that a condition similar to proliferative enteritis of swine, hamsters, and other species also occurs in laboratory rabbits.