Reactive arthritis following an outbreak of Salmonella typhimurium phage type 193 infection

Salmonella Exhibit Altered Cellular Localization in the Presence of HLA-B27 and Codistribute with Endo-Reticular Membrane

Salmonella enteritica (S. enteritica) induce and require unfolded protein response (UPR) pathways for intracellular replication. Salmonella infections can lead to reactive arthritis (ReA), which can exhibit associations with Human Leucocyte Antigen (HLA)-B^∗27 : 05. S. enteritica normally reside in a juxtanuclear position to the Golgi apparatus, representing the formation and residence within the Salmonella-containing vacuole (SCV). Changes in cellular localization of infecting Salmonella can alter their ability to replicate. We therefore used isogenic epithelial cell lines expressing physiological levels of HLA-B^∗27 : 05 heavy chain (HC) and a control HLA-B allele, HLA-B^∗35 : 01.HC to determine any changes in Salmonella localization within epithelial cells. Expression of HLA-B^∗27 : 05 but not HLA-B^∗35 : 01 was associated with a quantifiable change in S. enteritica cellular distribution away from the Golgi apparatus. Furthermore, the Salmonella requirements for UPR induction and the consequences of the concomitant endoplasmic reticulum (ER) membrane expansion were determined. Using confocal imaging, S. enteritica bacteria exhibited a significant and quantifiable codistribution with endo-reticular membrane as determined by ER tracker staining. Isogenic S. enterica Typhimurium mutant strains, which can infect but exhibit impaired intracellular growth, demonstrated that the activation of the UPR was dependent on an integral intracellular niche. Therefore, these data identify cellular changes accompanying Salmonella induction of the UPR and in the presence of HLA-B27.

Clinical profiles of post-infectious arthritis and transient synovitis of the hip in children

BACKGROUND

Acute inflammatory arthritides can present as a result of immune reaction following infections. Post-infectious arthritis and transient synovitis of the hip in children are included in this disease entity. The aim of this study was to describe the clinical profiles of post-infectious arthritis and transient synovitis of the hip in Thai children.

METHODS

A retrospective review was performed at a tertiary care hospital in Bangkok, Thailand from January 2005 to July 2017.

RESULTS

Eighty-six patients (56 boys and 30 girls) were included in this study. Mean age was 8.4 ± 4.8 years. Reactive arthritis was diagnosed in two patients (2.3%) following Salmonella spp. and Chlamydia trachomatis infections. Post-streptococcal reactive arthritis was present in 10 patients (11.6%). Transient synovitis of the hip was found in 30 patients (34.9%). Forty-four patients (51.2%) were clinically diagnosed with post-infectious arthritis. Mono/oligoarthritis was the most common clinical profile (84.9%). The distribution of lower-extremity involvement was as follows: hip, 47.6%; knee, 46.5%; and ankle joints, 30.2%. The documented preceding illness consisted mostly of upper respiratory tract symptoms (30.2%). Non-steroidal anti-inflammatory drugs were prescribed for 70 patients (81.4%).

CONCLUSION

Mono/oligoarthritis of the lower extremity was the main clinical profile. Preceding viral illness was documented in one-third of children. Reactive arthritis was rarely seen.

Association Between a History of Nontyphoidal Salmonella and the Risk of Systemic Lupus Erythematosus: A Population-Based, Case-Control Study

Objective

We investigated the correlation between nontyphoidal Salmonella (NTS) infection and systemic lupus erythematosus (SLE) risk.

Methods

This case-control study comprised 6,517 patients with newly diagnosed SLE between 2006 and 2013. Patients without SLE were randomly selected as the control group and were matched at a case-control ratio of 1:20 by age, sex, and index year. All study individuals were traced from the index date back to their NTS exposure, other relevant covariates, or to the beginning of year 2000. Conditional logistic regression analysis was used to analyze the risk of SLE with adjusted odds ratios (aORs) and 95% confidence intervals (CIs) between the NTS and control groups.

Results

The mean age was 37.8 years in the case and control groups. Females accounted for 85.5%. The aOR of having NTS infection were significantly increased in SLE relative to controls (aOR, 9.20; 95% CI, 4.51-18.78) in 1:20 sex-age matching analysis and (aOR, 7.47; 95% CI=2.08-26.82) in propensity score matching analysis. Subgroup analysis indicated that the SLE risk was high among those who dwelled in rural areas; had rheumatoid arthritis, multiple sclerosis, or Sjogren’s syndrome; and developed intensive and severe NTS infection during admission.

Conclusions

Exposure to NTS infection is associated with the development of subsequent SLE in Taiwanese individuals. Severe NTS infection and other autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, or Sjogren’s syndrome also contributed to the risk of developing SLE.

Enteric Pathogens and Reactive Arthritis: Systematic Review and Meta-Analyses of Pathogen-Associated Reactive Arthritis

The objective of this systematic review and meta-analysis was to estimate the proportion of postinfectious reactive arthritis (ReA) after bacterial enteric infection from one of four selected pathogens. We collected studies from PubMed, Web of Science, and Embase, which assessed the proportion of postinfectious ReA published from January 1, 2000 to April 1, 2018. Papers were screened independently by title, abstract, and full text; papers in English, Spanish, and Portuguese utilizing a case-control (CC) or cohort study design, with a laboratory confirmed or probable acute bacterial enteric infection and subsequent ReA, were included. The proportion of ReA cases was pooled between and across pathogens. Factors that can induce study heterogeneity were explored using univariate meta-regression, including region, sample size, study design, and ReA case ascertainment. Twenty-four articles were included in the final review. The estimated percentage of cases across studies describing Campylobacter-associated ReA (n = 11) was 1.71 (95% confidence interval [CI] 0.49-5.84%); Salmonella (n = 17) was 3.9 (95% CI 1.6-9.1%); Shigella (n = 6) was 1.0 (95% CI 0.2-4.9%); and Yersinia (n = 7) was 3.4 (95% CI 0.8-13.7%). Combining all four pathogens, the estimated percentage of cases that developed ReA was 2.6 (95% CI 1.5-4.7%). Due to high heterogeneity reflected by high I² values, results should be interpreted with caution. However, the pooled proportion developing ReA from studies with sample sizes (N) <1000 were higher compared with N > 1000 (6% vs. 0.3%), retrospective cohort studies were lower (1.1%) compared with CC or prospective cohorts (6.8% and 5.9%, respectively), and those where ReA cases are identified through medical record review were lower (0.3%) than those identified by a specialist (3.9%) or self-report (12%). The estimated percentage of people who developed ReA after infection with Campylobacter, Salmonella, Shigella, or Yersinia is relatively low (2.6). In the United States, this estimate would result in 84,480 new cases of ReA annually.

Expanding the spectrum of reactive arthritis (ReA): classic ReA and infection-related arthritis including poststreptococcal ReA, Poncet's disease, and iBCG-induced ReA

Reactive arthritis (ReA) is a form of sterile arthritis that occurs secondary to an extra-articular infection in genetically predisposed individuals. The extra-articular infection is typically an infection of the gastrointestinal tract or genitourinary tract. Infection-related arthritis is a sterile arthritis associated with streptococcal tonsillitis, extra-articular tuberculosis, or intravesical instillation of bacillus Calmette–Guérin (iBCG) therapy for bladder cancer. These infection-related arthritis diagnoses are often grouped with ReA based on the pathogenic mechanism. However, the unique characteristics of these entities may be masked by a group classification. Therefore, we reviewed the clinical characteristics of classic ReA, poststreptococcal ReA, Poncet’s disease, and iBCG-induced ReA. Considering the diversity in triggering microbes, infection sites, and frequency of HLA-B27, these are different disorders. However, the clinical symptoms and intracellular parasitism pathogenic mechanism among classic ReA and infection-related arthritis entities are similar. Therefore, poststreptococcal ReA, Poncet’s disease, and iBCG-induced ReA could be included in the expanding spectrum of ReA, especially based on the pathogenic mechanism.

Cohort profile of a US military population for evaluating pre-disease and disease serological biomarkers in rheumatoid and reactive arthritis: Rationale, organization, design, and baseline characteristics

Purpose

The etiology of several autoimmune disorders, including rheumatoid arthritis, remains unknown. While there are clear phases of disease progression, the mechanisms of transition between these phases are poorly understood. Additionally, treatment focuses on an alteration of the biological processes to prevent joint damage and functional decline. A goal is to potentially treat the disease during the preclinical phase to mitigate the disease process. Reactive arthritis is another rheumatologic condition known to be secondary to a distal infection. While prevention of infection would mitigate risk, serologic profiling patients with the disease may assist in the elucidation of potential disease risk factors. This study was initiated to enable an assessment of pre-disease biomarkers in patients newly diagnosed with rheumatoid arthritis and reactive arthritis.

Participants

A retrospective cohort of 500 rheumatoid and 500 reactive arthritis cases with 500 matched controls was drawn from a population of active component US military personnel. Appropriate inclusion criteria limited subject selection. Additionally, 4 serum samples (3 pre-disease and 1 disease-associated) were obtained for each case and control.

Findings to date

The established cohort provides the framework for novel exploration of the host response through serum profiling and seroepidemiology prior to disease onset.

Future plans

This study establishes the framework for the evaluation of novel serum biomarkers enabling the identification of signals prior to clinical disease that may enable disease prediction, elucidate disease pathogenesis and identify novel exposures leading to increased disease risk and/or disease severity.

Salmonella exploits HLA-B27 and host unfolded protein responses to promote intracellular replication

Objective

Salmonella enterica infections can lead to Reactive Arthritis (ReA), which can exhibit an association with human leucocyte antigen (HLA)-B*27:05, a molecule prone to misfolding and initiation of the unfolded protein response (UPR). This study examined how HLA-B*27:05 expression and the UPR affect the Salmonella life-cycle within epithelial cells.

Methods

Isogenic epithelial cell lines expressing two copies of either HLA-B*27:05 and a control HLA-B*35:01 heavy chain (HC) were generated to determine the effect on the Salmonella infection life-cycle. A cell line expressing HLA-B*27:05.HC physically linked to the light chain beta-2-microglobulin and a specific peptide (referred to as a single chain trimer, SCT) was also generated to determine the effects of HLA-B27 folding status on S. enterica life-cycle. XBP-1 venus and AMP dependent Transcription Factor (ATF6)-FLAG reporters were used to monitor UPR activation in infected cells. Triacin C was used to inhibit de novo lipid synthesis during UPR, and confocal imaging of ER tracker stained membrane allowed quantification of glibenclamide-associated membrane.

Results

S. enterica demonstrated enhanced replication with an altered cellular localisation in the presence of HLA-B*27:05.HC but not in the presence of HLA-B*27:05.SCT or HLA-B*35:01. HLA-B*27:05.HC altered the threshold for UPR induction. Salmonella activated the UPR and required XBP-1 for replication, which was associated with endoreticular membrane expansion and lipid metabolism.

Conclusions

HLA-B27 misfolding and a UPR cellular environment are associated with enhanced Salmonella replication, while Salmonella itself can activate XBP-1 and ATF6. These data provide a potential mechanism linking the life-cycle of Salmonella with the physicochemical properties of HLA-B27 and cellular events that may contribute to ReA pathogenesis. Our observations suggest that the UPR pathway maybe targeted for future therapeutic intervention.

The "Biology-First" Hypothesis: Functional disorders may begin and end with biology-A scoping review

While it is generally accepted that gastrointestinal infections can cause functional disturbances in the upper and lower gastrointestinal tract-known as postinfectious irritable bowel syndrome (PI-IBS) and functional dyspepsia (PI-FD)-it has still not been widely recognized that such an infection can also initiate functional non-intestinal diseases, and that non-intestinal infections can provoke both intestinal and non-intestinal functional disturbances. We conducted a scoping review of the respective literature and-on the basis of these data-hypothesize that medically unexplained functional symptoms and syndromes following an infection may have a biological (genetic, endocrine, microbiological) origin, and that psychological and social factors, which may contribute to the disease "phenotype," are secondary to this biological cause. If this holds true, then the search for psychological and social theories and factors to explain why one patient develops a chronic functional disorder while another does not is-at least for postinfectious states-misleading and detracts from exploring and identifying the true origins of these essentially biological disorders. The biopsychosocial model may, as the term implies, always begin with biology, also for functional (somatoform) disorders.

Induction of Hypergammaglobulinemia and Autoantibodies by Salmonella Infection in MyD88-Deficient Mice

Growing evidence indicates a link between persistent infections and the development of autoimmune diseases. For instance, the inability to control Salmonella infection due to defective toll-like receptor (TLR)/myeloid differentiation primary response 88 (MyD88) signaling has linked the development of persistent infections to a breakdown in B cell tolerance. However, the extent of immune dysregulation in the absence of TLR-MyD88 signaling remains poorly characterized. Here, we show that MyD88^−/− mice are unable to eliminate attenuated Salmonella enterica serovar Typhimurium, even when challenged with a low-dose inoculum (200 CFUs/mouse), developing a persistent and progressive infection when compared to wild-type (MyD88^+/+) animals. The splenic niche of MyD88^−/− mice revealed increased counts of activated, Sca-1-positive, myeloid subpopulations highly expressing BAFF during persistent Salmonella infection. Likewise, the T cell compartment of Salmonella-infected MyD88^−/− mice showed increased levels of CD4⁺ and CD8⁺ T cells expressing Sca-1 and CD25 and producing elevated amounts of IL-4, IL-10, and IL-21 in response to CD3/CD28 stimulation. This was associated with increased Tfh cell differentiation and the presence of CD4⁺ T cells co-expressing IFN-γ/IL-4 and IFN-γ/IL-10. Noteworthy, infected MyD88^−/− mice had enhanced serum titers of both anti-Salmonella antibodies as well as autoantibodies directed against double-stranded DNA, thyroglobulin, and IgG rheumatoid factor, positive nuclear staining with HEp-2 cells, and immune complex deposition in the kidneys of MyD88^−/− mice infected with live but not heat-killed Salmonella. Infection with other microorganisms (Acinetobacter baumanii, Streptococcus agalactiae, or Escherichia coli) was unable to trigger the autoimmune phenomenon. Our findings suggest that dysregulation of the immune response in the absence of MyD88 is pathogen-dependent and highlight potentially important genotype–environmental factor correlations.

Yersinia enterocolitica biotype 1A: a possible new trigger of reactive arthritis

Yersinia enterocolitica (YE) biotype 1A is generally considered non-pathogenic, and the role of it in causing reactive musculoskeletal complications is unclear. We evaluated the capability of YE biotype 1A to induce reactive arthritis (ReA) and other reactive musculoskeletal symptoms. Analysis of self-reported musculoskeletal symptoms was supplemented with a telephone interview (with a permission to acquire copies of patient files from a local physician or hospital) and/or clinical examination of subjects with recent musculoskeletal symptoms after a positive stool culture for YE. The diagnoses of ReA and reactive tendinitis and enthesitis (ReTe) were defined as "definite" when based on clinical examination and/or on interview by phone and "probable" when based solely on the questionnaire. Of 120 subjects, who reported musculoskeletal symptoms, 100 were included in the final analysis. Among these 100 patients, 68% had YE biotype 1A, 16% YE bio/serotype 4, and 1% biotype 2 infection; the remaining 15% had different YE-like strains or a non-biotypable strain. Of the 21 patients with ReA and of the 14 patients with ReTe, the diagnosis was definite in 9 and 7 patients and probable in 12 and 7 patients, respectively. The clinical picture of ReA caused by YE biotype 1A was similar with other bio/serotypes of YE. The definite ReA due to YE biotype 1A occurred in middle-aged adults (5 men, 4 women) with the most frequently affected joints being the knees and ankles. We suggest that YE biotype 1A should be taken into account as a new trigger of ReA.

Diversity of Antimicrobial Resistance Phenotypes in Salmonella Isolated from Commercial Poultry Farms

Salmonella remains the leading cause of foodborne illness in the United States, and the dissemination of drug-resistant Salmonellae through the food chain has important implications for treatment failure of salmonellosis. We investigated the ecology of Salmonella in integrated broiler production in order to understand the flow of antibiotic susceptible and resistant strains within this system. Data were analyzed from a retrospective study focused on antimicrobial resistant Salmonella recovered from commercial broiler chicken farms conducted during the initial years of the US FDA's foray into retail meat surveillance by the National Antimicrobial Resistance Monitoring System (NARMS). Sixty-three percentage of Salmonella were pan-susceptible to a panel of 19 antimicrobials used by the NARMS program. Twenty-five antimicrobial resistance phenotypes were observed in Salmonella isolated from two broiler chicken farms. However, Salmonella displaying resistance to streptomycin, alone, and in combination with other antibiotics was the most prevalent (36.3%) antimicrobial resistance phenotype observed. Resistance to streptomycin and sulfadimethoxine appeared to be linked to the transposon, Tn21. Combinations of resistance against streptomycin, gentamicin, sulfadimethoxine, trimethoprim, and tetracycline were observed for a variety of Salmonella enterica serovars and genetic types as defined by pulsed-field gel electrophoresis. There were within and between farm differences in the antibiotic susceptibilities of Salmonella and some of these differences were linked to specific serovars. However, farm differences were not linked to antibiotic usage. Analysis of the temporal and spatial distribution of the endemic Salmonella serovars on these farms suggests that preventing vertical transmission of antibiotic-resistant Salmonella would reduce carcass contamination with antibiotic-resistant Salmonella and subsequently human risk exposure.

Factors Associated with Sequelae of Campylobacter and Non-typhoidal Salmonella Infections: A Systematic Review

Despite the significant global burden of gastroenteritis and resulting sequelae, there is limited evidence on risk factors for sequelae development. We updated and extended previous systematic reviews by assessing the role of antibiotics, proton pump inhibitors (PPI) and symptom severity in the development of sequelae following campylobacteriosis and salmonellosis. We searched four databases, including PubMed, from 1 January 2011 to 29 April 2016. Observational studies reporting sequelae of reactive arthritis (ReA), Reiter's syndrome (RS), irritable bowel syndrome (IBS) and Guillain-Barré syndrome (GBS) following gastroenteritis were included. The primary outcome was incidence of sequelae of interest amongst cases of campylobacteriosis and salmonellosis. A narrative synthesis was conducted where heterogeneity was high. Of the 55 articles included, incidence of ReA (n = 37), RS (n = 5), IBS (n = 12) and GBS (n = 9) were reported following campylobacteriosis and salmonellosis. A pooled summary for each sequela was not estimated due to high level of heterogeneity across studies (I2 > 90%). PPI usage and symptoms were sparsely reported. Three out of seven studies found a statistically significant association between antibiotics usage and development of ReA. Additional primary studies investigating risk modifying factors in sequelae of GI infections are required to enable targeted interventions.

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There is no clear direction of the association between antibiotics and gastroenteritis triggered reactive arthritis.

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Precision of genomic methods and increased use of record linkage techniques may provide clarity.

Antibiotics are known to change the gut flora but little is known of their potential to cause complications in patients who have gastroenteritis. We conducted a systematic review of the existing evidence to assess the potential association of antibiotic usage in patients with gastroenteritis and the occurrence of complications such as reactive arthritis (ReA). The available evidence did not indicate a clear direction in the association of antibiotics and ReA. The lack of clarity in the association of antibiotics and ReA raises a call for further primary research on the role of medications in the development of complications of gastroenteritis.

Association between Giardia and arthritis or joint pain in a large health insurance cohort: could it be reactive arthritis?

This study aimed to assess the association between giardiasis and subsequent development of arthritis or joint pain using a retrospective cohort of individuals from a large administrative claims database in the United States. Using 2006-2010 data from MarketScan Commercial Claims and Encounters, we conducted a retrospective cohort study in people with an ICD-9-CM code for giardiasis (n = 3301) and persons without giardiasis (n = 14 612) individually matched on age, sex, and enrolment length. We used conditional logistic regression to model the association between giardiasis and arthritis or joint pain documented in the 6 months following initial giardiasis diagnosis or index date for matched controls. After adjusting for healthcare utilization rate, giardiasis was associated with a 51% increase in claims for arthritis or joint pain (odds ratio 1·51, 95% confidence interval 1·26-1·80). In age- and sex-stratified adjusted analyses, the association remained significant across all subgroups (age 0-19 years, age 20-64 years, males, and females). Findings from this study lend epidemiological support for the association between giardiasis and subsequent development of arthritis. Reactive arthritis might occur more frequently than has been reported in the literature. Further research is necessary to determine the mechanisms by which giardiasis could lead to arthritis.

Salmonella as an Inducer of Autoimmunity

A clear etiological link has been established between infection with several gram-negative enteric pathogens, including Salmonella spp., and the incidence of reactive arthritis (ReA), an autoimmune disease that largely affects the joints. ReA is sometimes referred to as Reiter's syndrome, particularly when accompanied by uveitis and urethritis. This review reviews the evidence etiologically linking Salmonella infection with autoimmune disease and addresses the roles that bacterial and host elements play in controlling disease outcome. ReA is an autoimmune disease that largely consists of painful joint inflammation but also can include inflammation of the eye, gastrointestinal tract, and skin. ReA is a member of a broad spectrum of chronic inflammatory disorders termed the seronegative spondyloarthropathies (SNSpAs) that includes ankylosing spondylitis (AS), psoriatic arthritis, and enteropathic arthritis. Salmonella species, as well as other enteric pathogens associated with postgastroenteritis ReA, are facultative intracellular gram-negative bacteria. Many studies have analyzed the association of the HLA class I molecule, HLA-B27, with SNSpAs. Whereas B27 has been shown to be present in 90 to 95% of cases of AS, the association of the B27 haplotype with other SNSpAs is more tenuous. The clear association between ReA and infection with Salmonella or other gram-negative enteric pathogens has led to the suggestion that the adaptive immune response to infection has an autoimmune component. In addition to various Salmonella species, other gram-negative enteric pathogens have been linked to the development of ReA. Given their close relationship to Salmonella, this review considers the involvement of Shigella species in ReA.

Systematic review and meta-analysis of the proportion of non-typhoidal Salmonella cases that develop chronic sequelae

The objective of this systematic review and meta-analysis was to estimate the proportion of cases of non-typhoidal salmonellosis (NTS) that develop chronic sequelae, and to investigate factors associated with heterogeneity. Articles published in English prior to July 2011 were identified by searching PubMed, Agricola, CabDirect, and Food Safety and Technology Abstracts. Observational studies reporting the number of NTS cases that developed reactive arthritis (ReA), Reiter's syndrome (RS), haemolytic uraemic syndrome (HUS), irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) or Guillain–Barré syndrome (GBS), Miller–Fisher syndrome (MFS) were included. Meta-analysis was performed using random effects and heterogeneity was assessed using the I² value. Meta-regression was used to explore the influence of study-level variables on heterogeneity. A total of 32 studies were identified; 25 reported on ReA, five reported on RS, seven reported on IBS, two reported on IBD, two reported on GBS, one reported on MFS, and two reported on HUS. There was insufficient data in the literature to calculate a pooled estimate for RS, HUS, IBD, GBS, or MFS. The pooled estimate of the proportion of cases of NTS that developed ReA and IBS had substantive heterogeneity, limiting the applicability of a single estimate. Thus, these estimates should be interpreted with caution and reasons for the high heterogeneity should be further explored.

Reactive arthritis

Reactive arthritis (ReA) is an immune-mediated seronegative arthritis that belongs to the group of spondyloarthropathies and develops after a gastrointestinal or genitourinary system infection. The condition is considered to be characterized by a triad of symptoms (conjunctivitis, arthritis and urethritis) although a constellation of other manifestations may also be present. ReA is characterized by psoriasiform dermatological manifestations that may resemble those of pustular psoriasis and, similar to guttate psoriasis, is a post-infectious entity. Also, the articular manifestations of the disorder are similar to those of psoriatic arthritis and both conditions show a correlation with HLA-B27. These facts have led several authors to suggest that there is a connection between ReA and psoriasis, listing ReA among the disorders related to psoriasis. However, the pathogenetic mechanism behind the condition is complex and poorly understood. Bacterial antigenicity, the type of host response (i.e. Th1/Th2 imbalance) and various genetic factors (i.e. HLA-B27 etc.) play an important role in the development of the disorder. It is unknown whether all the aforementioned factors are part of a mechanism that could be similar to, or share basic aspects with known psoriasis pathogenesis mechanisms.

Enteric pathogens and reactive arthritis: a systematic review of Campylobacter, salmonella and Shigella-associated reactive arthritis

Reactive arthritis (ReA) is a spondyloarthropathic disorder characterized by inflammation of the joints and tissues occurring after gastrointestinal or genitourinary infections. Diagnostic criteria for ReA do not exist and, therefore, it is subject to clinical opinion resulting in cases with a wide range of symptoms and definitions. Using standardized diagnostic criteria, we conducted a systematic literature review to establish the global incidence of ReA for each of the three most commonly-associated enteric pathogens: Campylobacter, Salmonella, and Shigella. The weighted mean incidence of reactive arthritis was 9, 12, and 12 cases per 1,000 cases of Campylobacter, Salmonella and Shigella infections respectively. To our knowledge, this is the first systematic review of worldwide data that use well-defined criteria to characterize diarrhoea-associated ReA. This information will aid in determining the burden of disease and act as a planning tool for public-health programmes.

Reactive arthritis induced by bacterial vaginosis: prevention with an effective treatment

We report a 42-year-old woman with reactive arthritis induced by bacterial vaginosis who presented with oligoarthritis with an additive form, arthralgia, and enthesitis. She hasn't had a history of diarrhea or dysuria or vaginal secretion, or sexually transmitted infections (STIs). The laboratory tests were normal except for a high erythrocyte sedimentation rate (ESR). Her pelvic examination revealed homogeneous white grey and malodorous vaginal discharge on the vaginal wall and Pap smear and Gram-stained smear of vaginal swab was consistent with bacterial vaginosis. She responded to metronidazole therapy and her six-month follow up hasn't shown recurrence of arthritis. As reactive arthritis (ReA) is a paradigm of a rheumatic disease in which the initiating infectious cause is known, so early use of antimicrobial drugs may prevent the development of musculoskeletal symptoms which are triggered by infections.

Reactive arthritis

Reactive arthritis (ReA) can be defined as the development of sterile inflammatory arthritis as a sequel to remote infection, often in the gastrointestinal or urogenital tract. Although no generally agreed-upon diagnostic criteria exist, the diagnosis is mainly clinical, and based on acute oligoarticular arthritis of larger joints developing within 2-4 weeks of the preceding infection. According to population-based studies, the annual incidence of ReA is 0.6-27/100,000. In addition to the typical clinical picture, the diagnosis of ReA relies on the diagnosis of the triggering infection. Human leucocyte antigen (HLA)-B27 should not be used as a diagnostic tool for a diagnosis of acute ReA. In the case of established ReA, prolonged treatment of Chlamydia-induced ReA may be of benefit, not only in the case of acute ReA but also in those with chronic ReA or spondylarthropathy with evidence of persisting chlamydia antigens in the body. In other forms of ReA, there is no confirmed evidence in favour of antibiotic therapy to shorten the duration of acute arthritis. The outcome and prognosis of ReA are best known for enteric ReA, whereas studies dealing with the long-term outcome of ReA attributable to Chlamydia trachomatis are lacking.

Bacterial agents in spondyloarthritis: a destiny from diversity?

The spondyloarthritides (SpAs) are a group of diseases that share clinical, radiographic and laboratory features; these arthritides also display a tendency for family aggregation. Given the intimate relationship that these types of arthritis share, it suggests that the SpAs might share a common aetiology. Of all the SpAs, the role of bacteria is most clearly defined in reactive arthritis. Tremendous recent insights into the pathophysiology of reactive arthritis have been made, demonstrating that the causative bacteria play a much more complex role than previously thought. The bacteria that are proven to cause reactive arthritis, one of the five types of SpA, will be reviewed and their role in the pathophysiology of reactive arthritis will be examined. The speculative data suggesting links between various other bacteria and the other types of SpAs will be critically analysed. Although these data are not definitive, when viewed using the paradigm that the SpAs might actually represent a common end point from several diverse starting points, they are provocative, suggesting that bacteria might, indeed, be aetiological for the entire group of SpAs.

The epidemiology of infectious gastroenteritis related reactive arthritis in U.S. military personnel: a case-control study

BACKGROUND

Reactive arthritis (ReA) is a recognized sequela of infectious gastroenteritis (IGE). However, the population-based incidence of IGE-related ReA is poorly defined, and the risk of disease has not previously been characterized in a military population. The intent of this study was to provide estimates of the incidence and morbidity associated with IGE-related ReA in the U.S. military population.

METHODS

Using active duty US military medical encounter data from the Defense Medical Surveillance System, we conducted a matched case-control study to assess the risk of ReA following IGE. Both specific and nonspecific case definitions were utilized to address ICD-9 coding limitations; these included specific ReA (Reiter's Disease or postdysenteric arthritis) and nonspecific arthritis/arthralgia (N.A.A) (which included several related arthropathy and arthralgia diagnoses). Incidence was estimated using events and the total number of active duty personnel for each year.

RESULTS

506 cases of specific ReA were identified in active duty personnel between 1999 and 2007. Another 16,365 cases of N.A.A. were identified. Overall incidence was 4.1 (95% CI: 3.7, 4.5) and 132.0 (95% CI, 130.0-134.0) per 100,000 for specific ReA and N.A.A, respectively. Compared to the youngest age category, the incidence of both outcomes increased 7-fold with a concurrent increase in symptom duration for cases over the age of 40. Specific IGE exposures were documented in 1.4% of subjects. After adjusting for potential confounders, there was a significant association between IGE and ReA (specific reactive arthritis OR: 4.42, 95% CI: 2.24, 8.73; N.A.A OR: 1.76, 95% CI: 1.49, 2.07).

CONCLUSIONS

Reactive arthritis may be more common in military populations than previously described. The burden of ReA and strong association with antecedent IGE warrants continued IGE prevention efforts.

Reactive Arthritis and Other Musculoskeletal Sequelae Following an Outbreak of Salmonella hadar in Castellon, Spain

Objective.

In 2005 a large outbreak of Salmonella hadar occurred in Spain following the consumption of commercial precooked roast chicken. We estimated the incidence and risk factors for reactive arthritis (ReA) and other musculoskeletal sequelae in the patients of this outbreak in 2 health departments of Castellon province.

Methods.

A prospective cohort study of the patients and their families was carried out. Clinical infection with Salmonella was considered as the exposure factor. The cohort was studied for ReA symptoms using a telephone questionnaire. Telephone interviews or medical examinations of subjects with musculoskeletal symptoms were conducted by a rheumatologist. Robust Poisson regression models were used in the analysis.

Results.

From the cohort of 262 people, 248 (94.7%) participated in the telephone survey, 155 with clinical salmonellosis (infected), 78 noninfected, and 15 with some symptoms but not clinical salmonellosis. One hundred one infected patients (65%) reported musculoskeletal symptoms, compared to 19 noninfected (24%) (adjusted relative risk = 2.60, 95% CI 1.73–3.90). Of the infected group, 16 ReA (incidence 10%, 95% CI 6.0–16.2), 7 enthesopathies, and 2 arthralgias were detected, and zero in the noninfected group. The risk factors for ReA were age, weight loss, and duration of diarrhea. Antibiotic treatment for the infection protected against symptoms of peripheral or axial arthritis (adjusted relative risk = 0.73, 95% CI 0.55–0.98).

Conclusion.

The incidence of ReA and musculoskeletal symptoms after the infection was high. The use of antibiotics for S. hadar infection offered some protection against musculoskeletal symptoms.

Reactive arthritis: clinical aspects and medical management

Reactive arthritis (ReA) is an inflammatory arthritis that arises after certain gastrointestinal or genitourinary infections, representing a classic interplay between host and environment. It belongs to the group of arthritidies known as the spondyloarthropathies. The classic syndrome is a triad of symptoms, including the urethra, conjunctiva, and synovium; however, the majority of patients do not present with this triad. Diagnostic criteria for ReA exist, but data suggest new criteria are needed. Epidemiologic and prospective studies have been difficult to perform because of over-reliance on the complete classic triad of symptoms and the different terms and eponyms used. Studies assessing various treatment strategies are ongoing.

Achilles tendinitis in Vibrio vulnificus sepsis: a rare presentation

Vibrio vulnificus infection commonly presents as sepsis or wound infection. A case of alcoholic liver cirrhosis developed acute left heel pain and swelling 2 days after ingesting raw fish. Two sets of blood cultures indicated V. vulnificus. HLA-B27 was negative. Ultrasonography revealed left Achilles tendinitis. Fluid aspirated from the left retrocalcaneal bursa was sterile. The patient recovered completely 3 weeks after treatment. To our knowledge, V. vulnificus septicaemia with Achilles tendinitis, which may be the only indication of reactive arthritis (ReA), has not been reported previously. Prompt recognition of this life-threatening infection and adequate treatment with antibiotics is vital.

Reactive arthritis: defined etiologies, emerging pathophysiology, and unresolved treatment

ReA is unique in that it is one of the few disease states of which there is a known trigger. This insight into disease initiation has led to great advances in the pathophysiology. Despite this detailed knowledge, the proper treatment remains elusive. In the years to come it is possible that the specific treatment will be dictated by the triggering microbe.

Mechanisms of disease: infection and spondyloarthritis

There is compelling evidence that some infections can initiate a chronic nonseptic arthritis. This has proved to be an important area of investigation into gene-environment interactions, particularly since HLA-B27 confers increased susceptibility to reactive arthritis. This research has investigated the microbiology of these events, and the strategies used by pathogens to induce chronic joint inflammation. Insights into the HLA-orchestrated immune response in this context have also shed light on the impact of HLA-B27 on immunity, which might provide insights into the mechanism of other HLA-B27-associated diseases. Despite the genetic link to reactive arthritis, there is no proven relationship between ankylosing spondylitis and an inciting infection. In general, most trials have found antibiotics to be ineffective in modifying the course of spondyloarthritis.

Reactive arthritis or post-infectious arthritis?

The term 'reactive arthritis' was first used in 1969 to describe the development of sterile inflammatory arthritis as a sequel to remote infection, often in the gastrointestinal or urogenital tract. The demonstration of antigenic material (e.g. Salmonella and Yersinia lipopolysaccharide), DNA and RNA, and, in occasional cases, evidence of metabolically active Chlamydia spp. in the joints has blurred the boundary between reactive and post-infectious forms of arthritis. No validated and generally agreed diagnostic criteria exist, but the diagnosis of reactive arthritis is mainly clinical based on acute oligoarticular arthritis of larger joints that develops within 2-4 weeks of the preceding infection. In about 25% of patients, the infection can be asymptomatic. Diagnosis of the triggering infection is very helpful for the diagnosis of reactive arthritis. This is mainly achieved by isolating the triggering infection (stools, urogenital tract) by cultures (stool cultures for enteric microbes) or ligase reaction (Chlamydia trachomatis). However, after the onset of arthritis, this is less likely to be possible. Therefore, the diagnosis must rely on various serological tests to demonstrate evidence of previous infection, but, these serological tests are unfortunately not standardized. Treatment with antibiotics to cure Chlamydia infection is important, but the use of either short or prolonged courses of antibiotics in established arthritis has not been found to be effective for the cure of arthritis. The long-term outcome of reactive arthritis is usually good; however, about 25-50% of patients, depending on the triggering infections and possible new infections, subsequently develop acute arthritis. About 25% of patients proceed to chronic spondyloarthritis of varying activity.

Incidencia de artritis reactiva y síntomas osteoarticulares después de un brote de Salmonella enteritidis fagotipo 14 b

BACKGROUND AND OBJECTIVE

We intended to estimate the prevalence of reactive arthritis (ReA) and other musculoskeletal sequelae after a foodborne outbreak of Salmonella enteritidis phago type 14 b in a banquet in Castellón in June 5th, 2004.

PATIENTS AND METHOD

A prospective cohort study was carried out with 125 subjects (90.6%) out of the banquet participants. Sixty-two symptomatic infected cases occurred, 33 with positive cultures of S. enteritidis phago type 14 b, and 54 non-infected subjects. After 4 months of the outbreak, all 125 subjects were studied by means of a symptoms questionnaire of ReA based on Buxton et al, administered by telephone. Medical examination of subjects with musculoskeletal symptoms, 29 of 30, was done by a rheumatologist. Relative risk (RR) with 95% confidence interval (CI) was estimated by Poisson regression models.

RESULTS

Any symptoms were reported by 32 (52%) of infected cases versus 13 (24%) of non-infected (RR adjusted = 2.49; 95% CI, 1.26-4.95); 20 (32%) infected cases reported muskuloskeletal symptoms compared to 4 (7%) non-infected (RR adjusted = 4.96; 95% CI, 1.64-15.04). The medical examination of the subjects with musculoskeletal symptoms revealed 3 infected cases with ReA (4.8%; 3/62). In addition, several reactive musculoskeletal sequelae associated with salmonellosis infection were found in 4 subjects (1 neck pain, 1 polyarthralgias, and 2 enthesopathy).

CONCLUSIONS

The occurrence of ReA was lower than other studies but the incidence of musculoskeletal symptoms was increased. The infection by Salmonella supposes a risk for joint symptoms that could be important taking into account the high incidence of salmonellosis.

Reactive arthritis

ReA consists of sterile axial or peripheral articular inflammation,enthesitis, and extra-articular manifestations. Most patients are HLA-B27 positive, although determining the B27 status of an individual patient is irrelevant. Exposure to specific bacterial antigens is usually the inciting factor. Diagnosis usually can be made by clinical examination and history. The current standard therapy is NSAIDs and physiotherapy, but molecular biologic treatment may ultimately become the mainstay in recalcitrant and severe ReA.

Emergence ofSalmonellaBlockley, possible association with long-term reactive arthritis, and antimicrobial resistance

We previously reported the case of a patient who became ill with Salmonella serotype Blockley after eating a chicken meal and who was still suffering symptoms of salmonella-reactive arthritis 10 years after the initial infection. The immunological consequences of infection were of concern and prompted a literature review because of the possibility that Salmonella Blockley may be more likely to cause long-term illness in certain patients than more common serovars. The review revealed the additional cause for concern of plasmid-borne extended spectrum beta-lactamases and the high frequency of integron-associated multidrug resistance in some isolates. The serovar was described in 1955 in the USA and Europe. It has become common in South East Asia and recently has been reported more often in Europe. A review of reactive arthritis outbreaks shows that information on the incidence and duration of the condition caused by serovars other than Salmonella serotype Enteritidis and Salmonella serotype Typhimurium is very limited. Rheumatologists can assist microbiologists and epidemiologists by reporting relevant cases of long-term reactive arthritis.

Reactive arthritis

Reactive arthritis (ReA) was known as Reiter's disease or Fiessinger-Leroy disease for nearly 100 years. However, during the past 30 years the disease has been known as reactive arthritis, a member of the spondyloarthritis family. Despite knowing the initiating event (infection) and genetic constitution (many patients have HLA-B27) of ReA, a model of interplay between environment and genetics, its pathogenesis is still incompletely known. This review covers the epidemiology, clinical features, treatment, and prognosis of ReA.

Early arthritis and infection

PURPOSE OF REVIEW

To summarize the recent literature on the association of infection with early arthritis, and to discuss the possible role of such infections with respect to the development of chronic rheumatic complications.

RECENT FINDINGS

Viral infections are frequently associated with arthritis. Alphaviruses belong to mosquito-borne viruses, one form of which (Sindbis virus) can in Scandinavia and Karelia cause acute arthritis with typical rash. The role of this infection leading to chronic erosive arthritis needs further prospective studies. Patients infected with HIV can have various forms of arthritis. The role of HIV virus as an arthritogenic agent is still debated. On the basis of population studies, Campylobacter infections seem to be increasing as causative infections in reactive arthritis. There is no role for prolonged antibiotic therapy to shorten the duration of acute reactive arthritis, but the possibility that such a treatment might reduce the development of chronic sequelae needs to be examined in a larger study. The role of preceding infection initiating the process of rheumatoid arthritis is still an option, the association being observed in about 20% of patients studied in the early phase of arthritis.

SUMMARY

Viral and microbial infections play a role in acute arthritis. The role of these infections in the development of chronic arthritis needs further prospective controlled studies.

Successful Treatment of Postvenereal Reactive Arthritis With Synovectomy and 3 Months’ Azithromycin

BACKGROUND

The effects of antibiotic therapy on the course of postvenereal reactive arthritis have not yet been elucidated.

OBJECTIVE

The objective of this study was to observe the clinical course and outcome of synovectomy and 3 months of azithromycin therapy in patients with reactive arthritis and previously diagnosed triggering bacteria.

METHODS

We performed an open, prospective study on 20 (14 male/6 female) patients with postvenereal reactive knee arthritis, aged 36.7 +/- 14.8 years, and with 16.5 +/- 20.4 months' duration of the disease. Detection of bacteria triggers was done by polymerase chain reaction, isolation and identification, and electron microscopy. Synovectomy was performed in all patients at entry into the study. Azithromycin was given at a dose of 500 mg per day for 5 days, and then 500 mg twice a week, during a 3-month period. Patients without remission were treated with combined antibiotic therapy using a macrolide, quinolone, and tetracycline for the next 4 months. Outcome evaluations of therapeutic efficacy and azithromycin safety were done after 1 and 3 months and 2 years of follow up.

RESULTS

Remission, defined by the absence of joint swelling and tenderness, and extraarticular signs, was reached after 3 months in 15 of 20 (75.0%) patients (P = 0.025). Of 5 patients with persistent knee arthritis, remission was achieved with combined antibiotic therapy in 4. Visual analog scale scores (P < 0.01), the number of patients (P = 0.002), and the number of samples (P = 0.01) with a positive finding of bacteria or their DNA were significantly lower after 3 months of therapy. During the azithromycin therapy, there were no significant adverse effects.

CONCLUSIONS

These patients with reactive arthritis did extremely well on the regimen described. In our study group, the number of patients and the number of samples with positive findings of bacteria or their DNA were lower after the antibiotic treatment combined with surgery, although not all bacteria were eradicated. Adverse effects of prolonged azithromycin administration were insignificant. This open treatment approach is recommended but does need a study with controls.

Management of reactive arthritis

Reactive arthritis (ReA) is an aseptic form of articular inflammation induced by infections mainly localised in the gastrointestinal (enteroarthritis) or urogenital (uroarthritis) tracts. The bacteria principally involved as causative agents are Chlamydia, Salmonella, Shigella, Campylobacter and Yersinia. The clinical picture is usually characterised by a mono-oligoarthritis of the lower limbs. Axial involvement is possible and extra-articular manifestations such as enthesitis, tenosynovitis, bursitis and dactylitis are frequent. NSAIDs and sulfasalazine are still the drugs most commonly used in the treatment of ReA. Steroids are administered when inflammatory symptoms are resistant to NSAIDs. Experiences with other DMARDs (disease modifying antirheumatic drugs) such as azathioprine, methotrexate and cyclosporin, have been sporadically reported and they can be employed in patients that are unresponsive to the more usual medicaments. The intake of antibacterials (tetracyclines) may be useful in uroarthritis but have not been so successful in enteroarthrits. In more aggressive cases, or when ReA evolves towards ankylosing spondylitis, TNF-alpha blockers could represent an effective choice.

Three month treatment of reactive arthritis with azithromycin: a EULAR double blind, placebo controlled study

OBJECTIVE

To determine the efficacy of weekly treatment with oral azithromycin for 13 weeks on the severity and resolution of reactive arthritis (ReA).

METHODS

186 patients from 12 countries were enrolled in a randomised, double blind, placebo controlled trial. Inclusion criteria were inflammatory arthritis of < or =6 swollen joints, and disease duration of < or =2 months. All patients received a single azithromycin dose (1 g) as conventional treatment for possible Chlamydia infection, and were then randomly allocated to receive weekly azithromycin or placebo. Clinical assessments were made at 4 week intervals for 24 weeks.

RESULTS

152 patients were analysable (34 failed entry criteria), with a mean (SD) age of 33.8 (9.4) and duration of symptoms 30.7 (17.5) days. Mean C reactive protein (CRP) was 48 mg/l, and approximately 50% of those typed were HLA-B27+, suggesting that the inclusion criteria successfully recruited patients with acute ReA. Treatment and placebo groups were well matched for baseline characteristics. There were no statistical differences for changes in any end point (swollen and tender joint count, joint pain, back pain, heel pain, physician and patient global assessments, and CRP) between the active treatment and placebo groups, analysed on an intention to treat basis or according to protocol completion. The time to resolution of arthritis and other symptoms or signs by life table analyses was also not significantly different. Adverse events were generally mild, but were more commonly reported in the azithromycin group.

CONCLUSIONS

This large trial has demonstrated that prolonged treatment with azithromycin is ineffective in ReA.

Effect of a three month course of ciprofloxacin on the late prognosis of reactive arthritis

BACKGROUND

The value of antibiotics in the treatment of reactive arthritis (ReA) is still controversial.

OBJECTIVES

To analyse the long term outcome of patients with ReA, treated with a three month course of ciprofloxacin or placebo.

METHODS

Patients who had had ReA and had participated in a double blind, placebo controlled trial on the effectiveness of ciprofloxacin 4-7 years earlier were invited to a clinical examination. Of the 71 patients who were included in the original study, 53 agreed to visit the clinic for an examination. Twenty six of 53 patients had originally received ciprofloxacin and 27 had belonged to the placebo group. Of these, 20 in the ciprofloxacin and 25 in the placebo group were HLA-B27 positive.

RESULTS

11/27 (41%) patients in the original placebo group had now developed chronic rheumatic disease, as compared with only 2/26 (8%) patients originally treated with ciprofloxacin (p=0.006). Two patients who originally had received placebo, none in the ciprofloxacin group had developed ankylosing spondylitis, and three patients in the original placebo group, none in the ciprofloxacin group had recurrent anterior uveitis. The same tendency was seen when several different measures were analysed. Of the patients with chronic spondyloarthropathy, 10 in the placebo and none in the ciprofloxacin group were HLA-B27 positive.

CONCLUSION

Analysis 4-7 years after the initial ReA suggests that a three month course of antibiotics in the acute phase may have a beneficial effect on the long term prognosis.

Microbial factors in spondyloarthropathies: insights from population studies

Infections and genetics play a role in the development of reactive arthritis. The clinical manifestations and severity of the features depend on the triggering infections and the epidemiologic setting. Reports from hospital-based series show the lowest frequency of reactive arthritis, but often, patients have severe arthritis associated with a high frequency of HLA-B27. At the population level, reactive arthritis occur in 7 to 15% of the infected subjects. The disease is usually mild, affects small joints, can be polyarticular, often rapidly disappears, and has a low association with HLA-B27. There also seems to be a change in the spectrum of triggering infections. Reports of Yersinia arthritis are less common, whereas arthritis in association with Campylobacter or Salmonella infections seems to be increasing. The role of early antimicrobial chemotherapy for the prevention of reactive arthritis needs to be studied.

Antibiotic treatment and long term prognosis of reactive arthritis

OBJECTIVE

To evaluate whether a three month course of lymecycline has an effect on the long term prognosis of reactive arthritis (ReA).

METHODS

In 1987-88 a double-blind controlled study with three month course of lymecycline/placebo was conducted. 17 of 23 patients treated at the outpatient department of Helsinki University Central Hospital volunteered to take part in a follow up study, where a physical examination were performed, and erythrocyte sedimentation rate, C reactive protein, rheumatoid factor, and radiographs of the lumbosacral spine and sacroiliac joints and of symptomatic peripheral joints were examined.

RESULTS

16/17 (94%) patients reported some kind of back pain and 10/17 (59%) peripheral joint symptoms during the follow up. Two patients had unilateral grade 1 sacroiliitis, one patient grade 4 sacroiliitis, and one patient bilateral grade 2 sacroiliitis. In one patient the disease had progressed to ankylosing spondylitis (AS), and in another to chronic spondyloarthropathy. In addition, two patients had small erosions in radiocarpal joints. No statistically significant differences were found between placebo and lymecycline groups in the development of chronic arthritis, sacroiliitis, or AS.

CONCLUSION

The results of the initial study showed that long term treatment with lymecycline in patients with acute ReA decreased the duration of arthritis in those with Chlamydia trachomatis triggered ReA, but not in other patients with ReA. Ten years after the acute arthritis one patient had developed AS, and three had radiological sacroiliitis, three patients had radiological changes at peripheral joints. Long term lymecycline treatment did not change the natural history of the disease.

Reactive arthritis: newer developments

Reactive arthritis (ReA) is characterized by an aseptic inflammatory articular involvement occurring in a genetically predisposed individual secondary to an infectious process localized outside the joint. ReA usually refers to an acute or insidious oligoarthritis process after enteric (enteroarthritis) or urogenital (uroarthritis) infection. Conventional antirheumatic therapeutic modalities based on nonsteroid anti-inflammatory drugs, sulfasalazine, and steroids are effective in the majority of patients. In more refractory cases, the use of second-line agents including methotrexate and more recently biological agents such as etanercept and infliximab has been found highly effective. The role of antibiotics remains not well established, although they appear to be effective in acute ReA of urogenital origin.

The role of infection in the pathogenesis of spondyloarthropathies with special reference to human leukocyte antigen-B27

Spondyloarthropathies consist of many inflammatory diseases that are closely associated with human leukocyte antigen (HLA)-B27. One of these diseases is reactive arthritis (ReA), which is a joint inflammation that occurs after infections that are caused by certain gram-negative bacteria. The importance of these infections as causative agents of ReA has been clearly established. It is not clear, however, whether these infections contribute to the development of other forms of spondyloarthropathies. The exact mechanism by which HLA-B27 influences disease susceptibility in spondyloarthropathies remains to be determined. The role of HLA-B27 as an antigen-presenting molecule is certainly important in the pathogenesis of these diseases; however, recent data indicate that this molecule may exhibit other functions unrelated to antigen presentation, which may be important in the pathogenesis of ReA. In this paper, the authors summarize the current knowledge of the role of infection in the spondyloarthropathies.