Assessment of the feasibility of serological monitoring and on-farm information about health status for the future meat inspection of fattening pigs.

Current macroscopic meat inspection cannot detect the most common pork-borne pathogens (Salmonella spp., Yersinia enterocolitica and Toxoplasma gondii). Furthermore, food chain information (FCI) may not provide sufficient data for visual-only inspection, which is supposed to be the common way of inspection of pigs in the European Union. Our observational study aimed to evaluate the serological monitoring and the clinical evaluation of on-farm health status of pigs and assess the feasibility of these data as part of the FCI in meat inspection. We studied the serological status of Salmonella spp., Yersinia spp. and T. gondii in pigs during the fattening period. Additionally, we evaluated the association between on-farm health status and meat inspection findings. On 57 indoor fattening pig farms in Finland, we collected blood samples (mean of 20 pigs/farm) and assessed the on-farm health (coughing, tail biting, lameness) at the end of the fattening period. We visited 34 of these farms also at the beginning of the fattening for sampling and on-farm health evaluation of the same pigs. Meat inspection results were obtained after slaughter for all 57 farms. Salmonella seroprevalence was low at the end of the fattening period: it was 17.6%, 10.6% or 1.9%, with the cut-off values of OD15% (recommended by the test manufacturer), OD20% (used by Danish monitoring programme) and OD40% (used by German monitoring programme), respectively. The overall seroprevalence of Salmonella spp. and Yersinia spp. increased significantly (P < 0.001) during the fattening period (from 8.1% to 17.2% and from 30.3% to 72.3%, respectively), while the seroprevalence of T. gondii remained low (<1%). The within-farm seroprevalences of Salmonella spp. and Yersinia spp. differed significantly between the farms and this farm-level serological data could be used as FCI for risk-based decisions to improve food safety. Such potentially feasible decisions could include additional carcass testing, carcass decontamination, carcass processing, slaughtering arrangements and improved biosecurity measures at the farm. However, risk mitigation targets and procedures must be carefully adjusted for each pathogen regarding also economic aspects. Tail biting observed on farm was associated with partial carcass condemnations and arthritis at slaughter. This information could be included in the FCI and used when making decisions regarding meat inspection procedure: visual-only or additional inspections.

Novel diagnostic ELISA test for discrimination between infections with Yersinia enterocolitica and Yersinia pseudotuberculosis.

Yersiniosis is a foodborne infection caused by Yersinia enterocolitica or Yersinia pseudotuberculosis. Although yersiniosis is most often self-limiting, some patients develop chronic infections, such as reactive arthritis, glomerulonephritis, or myocarditis, which require an antibiotic treatment. Whereas early infections can be diagnosed by direct detection of bacteria, chronic infections can only be identified by serological tests. At this point, a serological method for differentiation between infections with the two Yersinia species is important since antibiotic susceptibility of these bacteria is different. Traditional immunoassays do not distinguish between infections with Y. enterocolitica and Y. pseudotuberculosis. The only test that allows for this differentiation is Mikrogen's strip test where discrimination between the two types of infection is based on two recombinant bacterial proteins, MyfA and PsaA (specific for Y. enterocolitica and Y. pseudotuberculosis, respectively). Here, we show that Y. enterocolitica and Y. pseudotuberculosis, cultured under the conditions that mimic the natural rout of infection, express surface antigens different from MyfA and PsaA that can also be used in a discrimination test. Further, we describe a new ELISA that is based on the whole bacteria and recombinant MyfA and PsaA as antigens, and that allows the differentiation between infections with Y. enterocolitica and Y. pseudotuberculosis and simultaneous detection of yersiniosis.

The prevalence of Yersinia enterocolitica in game animals in Poland.

Natural reservoirs of Yersinia (Y.) enterocolitica comprise different animal species, but little is known about the role of wild animals in the epidemiology of yersiniosis. The aim of the study was to evaluate the prevalence of Y. enterocolitica among game animals in Poland. The bio-serotypes and the pathogenicity markers of the analyzed isolates were determined. The experimental material comprised rectal swabs from 857 free-living animals hunter-harvested over a period of 2 years (2013-2014) in hunting districts across Poland. The isolates from bacteriological studies were confirmed by PCR and bio-serotyped based on the results of biochemical and agglutination tests. In the group of the 218 analyzed isolates of Y. enterocolitica, 133 were derived from wild boars, 70 from red deer, 11 from roe deer and 4 from fallow deer, and they accounted for 61.0%, 32.1%, 5.1% and 1.8% of all isolates, respectively. Bio-serotyping assays revealed that 91.7% of the examined isolates belonged to biotype 1A (200/218). The remaining 18 isolates belonged to bio-serotypes 1B/NI (3/218, 1.4%), 1B/O:8 (1/218, 0.5%), 2/NI (6/218, 2.8%), 2/O:27 (1/218, 0.5%), 2/O:3 (1/218, 0.5%), 2/O:9 (2/218, 0.9%), 3/NI (2/218, 0.9%), 4/O:3 (1/218, 0.5%) and 4/O:9 (1/218, 0.5%). The ail gene, a suggestive virulence gene for Y. enterocolitica, has been found in 30 isolates from 20 wild boars, in 6 isolates from red deer, and in 1 isolate from roe deer. Our study demonstrated that Y. enterocolitica is frequently isolated from game animals in Poland, which poses a risk of spreading these infectious agents to other animal species and humans.

Role of ß1 integrins and bacterial adhesins for Yop injection into leukocytes in Yersinia enterocolitica systemic mouse infection.

Injection of Yersinia outer proteins (Yops) into host cells by a type III secretion system is an important immune evasion mechanism of Yersinia enterocolitica (Ye). In this process Ye invasin (Inv) binds directly while Yersinia adhesin A (YadA) binds indirectly via extracellular matrix (ECM) proteins to ß1 integrins on host cells. Although leukocytes turned out to be an important target of Yop injection by Ye, it was unclear which Ye adhesins and which leukocyte receptors are required for Yop injection. To explain this, we investigated the role of YadA, Inv and ß1 integrins for Yop injection into leukocytes and their impact on the course of systemic Ye infection in mice. Ex vivo infection experiments revealed that adhesion of Ye via Inv or YadA is sufficient to promote Yop injection into leukocytes as revealed by a ß-lactamase reporter assay. Serum factors inhibit YadA- but not Inv-mediated Yop injection into B and T cells, shifting YadA-mediated Yop injection in the direction of neutrophils and other myeloid cells. Systemic Ye mouse infection experiments demonstrated that YadA is essential for Ye virulence and Yop injection into leukocytes, while Inv is dispensable for virulence and plays only a transient and minor role for Yop injection in the early phase of infection. Ye infection of mice with ß1 integrin-depleted leukocytes demonstrated that ß1 integrins are dispensable for YadA-mediated Yop injection into leukocytes, but contribute to Inv-mediated Yop injection. Despite reduced Yop injection into leukocytes, ß1 integrin-deficient mice exhibited an increased susceptibility for Ye infection, suggesting an important role of ß1 integrins in immune defense against Ye. This study demonstrates that Yop injection into leukocytes by Ye is largely mediated by YadA exploiting, as yet unknown, leukocyte receptors.

Association between microbiological and serological prevalence of human pathogenic Yersinia spp. in pigs and pig batches.

Pigs are the main reservoir of human pathogenic Y. enterocolitica, and the microbiological and serological prevalence of this pathogen differs between pig farms. The infection status of pig batches at moment of slaughter is unknown while it is a possibility to classify batches. A relation between the presence of human pathogenic Yersinia spp. and the presence of antibodies could help to predict the infection of the pigs prior to slaughter. Pigs from 100 different batches were sampled. Tonsils and pieces of diaphragm were collected from 7047 pigs (on average 70 pigs per batch). The tonsils were analyzed using a direct plating method and the meat juice collected from the pieces of diaphragm was analyzed by Enzyme Linked ImmunoSorbent Assay. The microbiological and serological results were compared using a mixed-effects logistic regression at pig and batch level. Yersinia spp. were found in 2031 (28.8%) pigs, antibodies were present in 4692 (66.6%) pigs. According to the logistic regression, there was no relation at pig level between the presence of Yersinia spp. in tonsils and the presence of antibodies. Contrarily, at batch level, a mean activity value of 37 Optical Density (OD)% indicated a Yersinia spp. positive farm and the microbiological prevalence in pig batches could be estimated before shipment to the slaughterhouse. This offers the opportunity to classify batches based on their potential risk to contaminate carcasses with human pathogenic Yersinia spp.

Association between plasma antibody response and protection in rainbow trout Oncorhynchus mykiss immersion vaccinated against Yersinia ruckeri.

A key hallmark of the vertebrate adaptive immune system is the generation of antigen-specific antibodies from B cells. Fish are the most primitive gnathostomes (jawed vertebrates) possessing an adaptive immune system. Vaccination of rainbow trout against enteric redmouth disease (ERM) by immersion in Yersinia ruckeri bacterin confers a high degree of protection to the fish. The immune mechanisms responsible for protection may comprise both cellular and humoral elements but the role of specific immunoglobulins in this system has been questioned and not previously described. The present study demonstrates significant increase in plasma antibody titers following immersion vaccination and significantly reduced mortality during Y. ruckeri challenge.Rainbow trout were immersion-vaccinated, using either a commercial ERM vaccine (AquaVac™ ERM vet) or an experimental Y. ruckeri bacterin. Half of the trout vaccinated with AquaVac™ ERM vet received an oral booster (AquaVac™ ERM Oral vet). Sub-groups of the fish from each group were subsequently exposed to 1 x 109 CFU Y. ruckeri/ml either eight or twenty-six weeks post vaccination (wpv). All vaccinated groups showed 0% mortality when challenged, which was highly significant compared to the non-vaccinated controls (40 and 28% mortality eight and twenty-six weeks post vaccination (wpv), respectively) (P<0.0001). Plasma samples from all groups of vaccinated fish were taken 0, 4, 8, 12, 16 and 26 wpv. and Y. ruckeri specific IgM antibody levels were measured with ELISA. A significant increase in titers was recorded in vaccinated fish, which also showed a reduced bacteremia during challenge. In vitro plasma studies showed a significantly increased bactericidal effect of fresh plasma from vaccinated fish indicating that plasma proteins may play a role in protection of vaccinated rainbow trout.

The influence of experimental Yersinia enterocolitica infection on the pregnancy course in sows--preliminary studies. II. Antibodies, C-reactive proteins and haptoglobin as an immunological response.

The aim of the study was to determine the time of emergence and level of Y. enterocolitica antibodies in pregnant sows challenged orally with Y. enterocolitica in particular trimesters of pregnancy (groups I, II and III, respectively) and also the assignation of its influence on the CRP and Hp concentration in sera of pigs. Levels of antibodies measured by tube agglutination test increased slowly from 2 weeks post infection (wpi) and positive results were obtained not in all animals. In ELISA, in 2 weeks in all groups of infected animals high levels of antibodies against Y. enterocolitica were formed and lasted up to the end of the experiment. In newborn piglets in all groups, a significant decrease in antibody levels 6 weeks after birth was observed in both agglutination and ELISA tests. Concentrations of CRP as Hp in all groups of infected animals increased in 1 week post infection. Statistically significant differences (P < or = 0.05) between CRP levels in groups I and II (46-fold and 44-fold) as well as III (29-fold) were revealed. In case of Hp, statistically significant differences between groups of animals in the first week post infection were not observed. Our findings indicate that Y. enterocolitica infection evoked strong and long-lasting immunological reaction in the form of specific antibodies production in all inoculated animals. The significant increase in CRP and moderate increase in Hp concentrations in the sera of pregnant sows also occurred. However, relationships between colostrums antibody levels in piglets' sera and phase of pregnancy when the Y. enterocolitica infection happened in sows were not observed.

[Effect of Paenibacillus polymyxa lectin on cytokine status of animals].

AIM: To study effect of lectin L II of Paenibacillus polymyxa 1460 on cytokine status of mice during modeling of infections caused by Staphylococcus, Escherichia and Yersinia. MATERIALS AND METHODS: Lectin LII of P. polymyxa 1460, bacterial cultures Staphylococcus aureus 209-P, Escherichia coli O1, and Yersinia enterocolitica 12 were used. Mice were inoculated intraperitoneally with 0.2 ml of suspension of bacterial culture grown during 24 hours (5,000 m.c./ml). Lectin (0.4 mcg/ml) in dose 0.2 ml was administered 24 h before and 1 h after inoculation. Serum samplesfrom sacrificed animals were obtained 1, 6, and 24 hours after inoculation and concentrations of IL-1, IL-6, and TNF-alpha were measured in them using optical density values. RESULTS: It was established that level of TNF-alpha in serum decreased during staphylococcal infection, whereas levels of IL-1 and IL-6 decreased during all modeled infections. Ability for correction of cytokine balance in organism of experimental animals by administration of lectin 24 h before and 1 h after inoculation with bacteria was demonstrated. CONCLUSION: Presented studies testify to the effect of bacterial lectin on cytokine-production activity of macrophages during phagocytosis of bacteria and infectious process.

Development of adaptive immunity in rainbow trout, Oncorhynchus mykiss (Walbaum) surviving an infection with Yersinia ruckeri.

Development of adaptive immunity in rainbow trout (Oncorhynchus mykiss) surviving a primary infection with 5x10(5)CFU Yersinia ruckeri O1 (LD(50) dose) was investigated by transcriptome analysis of spleen tissue. These fish surviving a primary infection showed also a significantly increased survival following a secondary infection (same dose) when compared to naïve trout. The weight of the rainbow trout spleen doubled during the first 14 days of the primary infection but the affected organs subsequently recovered normal weight which remained constant during the re-infection period. Gene transcription in the spleen was measured using Quantitative real-time RT-PCR (qPCR). Samples taken 8h.p.i., 1, 3, 7, 14 and 28 d.p.i. were compared to PBS-injected control fish sampled at the same time points. The investigated cytokines and chemokines comprised interleukin (IL)-1beta, IL-1 receptor antagonist (Ra), IL-6, IL-8, IL-10, IL-11 and IFN-gamma, IL-1 receptor I and II (IL-RI and IL-RII). Transcript levels of genes encoding cytokines and receptors were increased during the primary infection but not during the secondary infection. Changes of T cell occurrence or activity in the spleen during the infections were inferred from the transcript level of T cell receptor (TCR), CD4 and CD8alpha genes. No alteration in the expression of MHC class ll and immunoglobulin (Ig)M and IgT was detected during the experiment. The amount of Y. ruckeri O1 in the spleen was measured with a Y. ruckeri 16S ribosomal RNA specific qPCR and this parameter was correlated to the expression of IL-1beta, IL-8 and IL-10 genes with a peak expression at 3d.p.i. (first infection). The low transcript levels of the bacterial gene and the hosts' immune genes during the re-infection can be interpreted as a result of development of adaptive immunity. This would explain the relatively fast elimination of the bacteria during the secondary infection whereby the activation of cytokines becomes less pronounced.

Yersinia enterocolitica infection in diarrheal patients.

In this study, we hoped to provide valuable clinical information on yersiniosis for clinicians. Two thousand six hundred stool samples were collected from in- and outpatients with diarrhea, which were tested with both culture method and real-time polymerase chain reaction (RT-PCR). In total, 188 positive samples were detected by RT-PCR (178) and culture method (160), while the incidence was about 7.23%. The detection rate of RT-PCR was significantly higher than culture method and a higher incidence in autumn-winter was also noticeably identified than in spring-summer. Infection sources mostly focused on unboiled foods (101) and pets (45), while clinical manifestation mainly presented as gastroenteritis (156), pseudoappendicitis (32), and extraintestinal complications (46). The morbidity of extraintestinal complications in adults was significantly higher than in children and it was the same for high-risk patients between adults over the age of 60 years (4.7%) and children under the age of 3 years (1.4%), whereas the constituent ratio of children versus adults with yersiniosis in different systems was not significant. Of 160 isolates tested for antimicrobial susceptibility, the majority were susceptible to third-generation cephalosporins, aminoglycosides, fluoroquinolones, and trimethoprim-sulfamethoxazole, whereas only a small portion was susceptible to the first-generation cephalosporins and penicillins. During autumn-winter months, clinicians should pay more attention to clinical manifestation, early diagnosis, and treatment with susceptible antibiotics of yersiniosis and its complications, targeting high-risk patients.

Too early to dismiss Yersinia enterocolitica infection in the aetiology of Graves' disease: evidence from a twin case-control study.

BACKGROUND: Yersinia enterocolitica (YE) infection has long been implicated in the pathogenesis of Graves' disease (GD). The association between YE and GD could, however, also be due to common genetic or environmental factors affecting the development of both YE infection and GD. This potential confounding can be minimized by investigation of twin pairs discordant for GD. AIM: To examine whether YE infection is associated with GD. DESIGN: We first conducted a classical case-control study of individuals with (61) and without (122) GD, and then a case-control study of twin pairs (36) discordant for GD. METHODS: Immunoglobulin (Ig)A and IgG antibodies to virulence-associated Yersinia outer membrane proteins (YOPs) were measured. MAIN OUTCOME MEASURES: The prevalence of YOP IgA and IgG antibodies. RESULTS: Subjects with GD had a higher prevalence of YOP IgA (49%vs. 34%, P = 0.054) and YPO IgG (51%vs. 35%, P = 0.043) than the external controls. The frequency of chronic YE infection, reflected by the presence of both IgA and IgG YOP antibodies, was also higher among cases than controls (49%vs. 33%, P = 0.042). Similar results were found in twin pairs discordant for GD. In the case-control analysis, individuals with GD had an increased odds ratio (OR) of YE infection: IgA 1.84 (95% CI 0.99-3.45) and IgG 1.90 (95% CI 1.02-3.55). In the co-twin analysis, the twin with GD also had an increased OR of YE infection: IgA 5.5 (95% CI 1.21-24.81) and IgG 5.0 (95% CI 1.10-22.81). CONCLUSION: The finding of an association between GD and YE in the case-control study and within twin pairs discordant for GD supports the notion that YE infection plays an aetiological role in the occurrence of GD, or vice versa. Future studies should examine the temporal relationship of this association in more depth.

[Infections of the gastrointestinal system--risk of transmission with blood and blood components]. / Zakazenia przewodu pokarmowego--ryzyko przeniesienia przez krew i jej skladniki.

The Yersinia genus belongs to the Enterobacteriacae family and comprises strains pathogenic for humans, which causes diseases of the gastrointestinal system. The infection can be transmitted with blood and blood components causing sepsis. The paper presents Yersinia enterocolitica complications after transfusion of blood and blood components as well as the frequency of occurrence and preventive measures.

[Laboratory diagnosis of Yersinia infection and its improvement].

Results of the bacteriological and serological tests of patients with Y. enterocolitica and Y. pseudotuberculosis infections for the period from 1994 to 2004 were analyzed. Main reasons of imperfect laboratory diagnostics were revealed, such as, low sensitivity of bacteriologic test, nonobservance of existing recommendations on diagnostics of Yersinia infections, performing of single but not repeated serologic test, absence of necessary laboratory equipment. Main ways of improving of quality of Y. enterocolitica infections and differential diagnostics were of Y. pseudotuberculosis defined.

Acute renal dysfunction in salmonella gastroenteritis.

GOALS: To determine the incidence of renal function deterioration in adult patients with Salmonella infection. BACKGROUND: Renal impairment has been described during severe Salmonella infection and is mainly due to shock, dehydration, or rhabdomyolysis. However, it is unclear whether less severe Salmonella infection also has an impact on kidney function. STUDY: We retrospectively reviewed over a 2-year period the data of all hospitalized adult patients with microbiologically proven gastrointestinal infection. Different biologic parameters were compared between patients infected with Salmonella and patients with other gastrointestinal infections. RESULTS: One hundred and seven patients with positive stool cultures were identified; 44 of them had proven Salmonella infection. Renal dysfunction, defined as an increase in serum creatinine above 1.5 mg/dL in men and above 1.3 mg/dL in women, was observed in 16 (36%) patients infected by Salmonella but only in 3 (5%) comparators (P<0.0001). Hydration status and creatine kinase levels were not different in patients affected by Salmonella as compared with other pathogens. Kidney function recovered in all but 1 patient. CONCLUSIONS: Salmonella gastroenteritis in adults is frequently accompanied by renal dysfunction that is caused by mechanisms other than dehydration or rhabdomyolysis.

The serodiagnosis of human infections with Yersinia enterocolitica and Yersinia pseudotuberculosis.

The techniques of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting were evaluated for the serodiagnosis of human infections with Yersinia enterocolitica and Yersinia pseudotuberculosis. Lipopolysaccharide (LPS) was prepared from strains comprising four serogroups of Y. enterocolitica and five serogroups of Y. pseudotuberculosis, tested against 200 sera submitted to the Laboratory of Enteric Pathogens for routine serodiagnosis, and shown to contain antibodies to Yersinia LPS by agglutination. Forty four sera were found to contain antibodies that bound to one of the LPS preparations used in the immunoassay. Thirty five of the sera contained antibodies to the LPS of Y. enterocolitica O3, whilst three contained antibodies to the LPS of Y. enterocolitica O5, 27 and Y. enterocolitica O9 LPS respectively. Two sera had antibodies to the LPS of Y. pseudotuberculosis II and a single serum contained antibodies to Y. pseudotuberculosis IV. The SDS-PAGE-immunoblotting procedure described proved to be a reliable procedure for the serodiagnosis of infections with Y. enterocolitica and Y. pseudotuberculosis.

The diagnostic value of serum interleukins 6 and 8 in children with acute gastroenteritis.

OBJECTIVES: Early identification of the pathogen causing acute gastroenteritis in children helps the physicians managing the disease and prevents unnecessary antibiotic treatment. C-reactive protein (CRP), interleukin (IL) 6 and IL-8 play a major role in immune responses and have been studied in a large number of infectious and noninfectious inflammatory diseases. The purpose of this study was to determine the serum IL-6 and IL-8 concentrations early in the course of acute gastroenteritis to see if these cytokines were useful diagnostic markers in differentiating viral from bacterial gastroenteritis. METHODS: Interleukin 6, IL-8 and CRP were measured in 18 patients with bacterial gastroenteritis, 21 patients with viral gastroenteritis and 17 healthy children. RESULTS: Interleukin 6 and CRP concentrations in patients with bacterial gastroenteritis were significantly higher than those in patients with viral gastroenteritis and healthy controls (P < 0.001). IL-8 concentrations in patients with viral and bacterial gastroenteritis were both increased and were not statistically different. IL-6 and IL-8 levels had diagnostic sensitivities of 79% and 50% and specificities of 86% and 67%, respectively. The combination of IL-6 and CRP had a sensitivity of 94%, specificity of 71%, a positive predictive value of 74% and a negative predictive value of 93.75%. CONCLUSIONS: Serum IL-6 may be a useful marker for early differentiation of viral and bacterial gastroenteritis in children, especially in combination with CRP.

Seroprevalence of brucellosis, tularemia, and yersiniosis in wild boars (Sus scrofa) from north-eastern Germany.

Brucellosis and tularemia are classical zoonotic diseases transmitted from an animal reservoir to humans. Both, wildlife and domestic animals, contribute to the spreading of these zoonoses. The surveillance of the animal health status is strictly regulated for domestic animals, whereas systematic disease monitoring in wildlife does not exist. The aim of the present study was to provide data on the prevalence of anti-Brucella, anti-Francisella and anti-Yersinia antibodies in wild boars from North-Eastern Germany to assess public health risks. A total of 763 sera of wild boars from Mecklenburg-Western Pomerania hunted in 1995/1996 were tested using a commercially available Brucella suis ELISA, an in-house lipopolysaccharide (LPS)-based Francisella ELISA, and commercially available Western blot kits for the detection of anti-Francisella and anti-Yersinia antibodies. The Yersinia enterocolitica O:9 LPS is able to induce serological cross-reactions indistinguishable from brucellosis due to a similar immunodominant epitope in the Brucella O-polysaccharide. The Yersinia Western blot assay was, therefore, based on five recombinant Yersinia outer proteins which have been proved to be specific for the serodiagnosis of yersiniosis. Anti-Brucella, anti-Francisella and anti-Yersinia antibodies were detected in 22.0%, 3.1%, and 62.6% of the wild boars, respectively. The high seroprevalence of tularemia and brucellosis in wild boars indicates that natural foci of these zoonoses are present in wildlife in Germany. However, the impact of transmission of zoonotic pathogens from wildlife to livestock is unknown. Only careful and systematic monitoring will help to prevent the (re)emergence of these zoonotic diseases in domestic animals and consequently human infection.

Evaluation of a western blot method for the detection of Yersinia antibodies: evidence of serological cross-reactivity between Yersinia outer membrane proteins and Borrelia burgdorferi.

Yersinia enterocolitica and Yersinia pseudotuberculosis have been identified as causative organisms of reactive arthritis in humans. We evaluated a Western blot assay which uses Yersinia outer membrane proteins as antigens for the detection of Yersinia antibodies as a replacement for the complement fixation (CF) assay. Clinical agreement, sensitivity, and specificity were determined by testing 19 positive and 21 negative serum samples by the CF assay, Western blot assay, and enzyme-linked immunosorbent assay (ELISA). The CF assay and ELISA were compared to the Western blot assay, which was the reference method used in this study. Sera with antibodies that could potentially cross-react with Yersinia were also tested by the Western blot assay. The agreement, sensitivity, and specificity of the CF method were 61%, 26%, and 95%, respectively; and those for the ELISA were 89%, 95%, and 82%, respectively. The prevalences of Yersinia antibodies in 50 healthy donors were 6% for immunoglobulin G (IgG), 2% for IgA, and 2% for IgM. Sera positive for Bartonella henselae, Brucella, Chlamydia pneumoniae, and Rickettsia rickettsii antibodies showed cross-reactivity by the Western blot assay. The highest cross-reactivity was observed with Borrelia burgdorferi; 5 of 11 (45%) specimens were cross-reactive by the IgM-specific assay. Overall, the Western blot assay performs acceptably and is more sensitive than the CF assay, warranting replacement of the CF assay in the laboratory. Due to the evidence of cross-reactivity, particularly with B. burgdorferi, which can cause an oligoarthritis similar to reactive arthritis, the diagnosis of reactive arthritis should be based on clinical findings and complete serologic analysis of the potential causative infectious pathogens.

Production of autoantibodies associated with polyclonal activation in Yersinia enterocolitica O: 8-infected mice.

Polyclonal lymphocyte stimulation is one of the immunomodulatory mechanisms induced by arthritogenic pathogens. In this study we examined the polyclonal activation potential of a virulent strain of Y. enterocolitica serotype O: 8 (WA 2707(+)) and its plasmidless isogenic pair (WA 2707(-)). SPF Swiss mice were infected intragastrically and spleen cells were obtained on days 7, 14, 21, 28, 35 and 42 after infection. The number of cells secreting nonspecific immunoglobulins of IgG, IgM and IgA isotypes was determined by the ELISPOT technique. The presence of serum-specific antibodies was investigated by ELISA and the presence of autoantibodies by dot-blot assay. Although the patterns of infection of the two bacterial strains were almost the same, only the animals infected with the virulent strain presented clinical anomalies. Neither arthritic nor inflammatory signs were observed in the joints of the infected animals. The greatest activation observed was that of the nonspecific IgM-secreting cells, and their peak of secretion occurred between the 28th and the 42nd day after infection, for both strains of Y. enterocolitica O: 8. Only the animals infected with the virulent strain (WA 2707(+)) produced IgG-specific antibodies in the serum, from the 28th day after infection. The serum of animals infected with either strain showed reactivity to all the autologous constituents tested, mainly on the 28th and 42nd day after infection. It was concluded that infection of mice with either the virulent strain of Y. enterocolitica O: 8 or with its plasmidless isogenic pair resulted in the polyclonal activation of the splenic B lymphocytes including some autoreactive clones.