Genome sequence and comparative microarray analysis of serotype M18 group A Streptococcus strains associated with acute rheumatic fever outbreaks

Acute rheumatic fever (ARF), a sequelae of group A Streptococcus (GAS) infection, is the most common cause of preventable childhood heart disease worldwide. The molecular basis of ARF and the subsequent rheumatic heart disease are poorly understood. Serotype M18 GAS strains have been associated for decades with ARF outbreaks in the U.S. As a first step toward gaining new insight into ARF pathogenesis, we sequenced the genome of strain MGAS8232, a serotype M18 organism isolated from a patient with ARF. The genome is a circular chromosome of 1,895,017 bp, and it shares 1.7 Mb of closely related genetic material with strain SF370 (a sequenced serotype M1 strain). Strain MGAS8232 has 178 ORFs absent in SF370. Phages, phage-like elements, and insertion sequences are the major sources of variation between the genomes. The genomes of strain MGAS8232 and SF370 encode many of the same proven or putative virulence factors. Importantly, strain MGAS8232 has genes encoding many additional secreted proteins involved in human-GAS interactions, including streptococcal pyrogenic exotoxin A (scarlet fever toxin) and two uncharacterized pyrogenic exotoxin homologues, all phage-associated. DNA microarray analysis of 36 serotype M18 strains from diverse localities showed that most regions of variation were phages or phage-like elements. Two epidemics of ARF occurring 12 years apart in Salt Lake City, UT, were caused by serotype M18 strains that were genetically identical, or nearly so. Our analysis provides a critical foundation for accelerated research into ARF pathogenesis and a molecular framework to study the plasticity of GAS genomes.

Rheumatic fever in the 21st century

In the first half of the twentieth century, the group A streptococcus (GAS) was established as the sole etiologic agent of acute rheumatic fever (ARF). In the century's latter half, the clinical importance of variation in the virulence of strains of GAS has become clearer. Although still obscure, the pathogenesis of ARF requires primary infection of the throat by highly virulent GAS strains. These contain very large hyaluronate capsules and M protein molecules. The latter contain epitopes that are cross-reactive with host tissues and also contain superantigenic toxic moieties. In settings where ARF has become rare, GAS pharyngitis continues to be common, although it is caused by GAS strains of relatively lower virulence. These strains, however, colonize the throat avidly and stubbornly. Molecularly distinct pyoderma strains may cause acute glomerulonephritis, but they are not rheumatogenic, even though they may secondarily colonize and infect the throat. Guidelines for the diagnosis, treatment, and prevention of GAS pharyngitis and ARF are reviewed with particular reference to the prevalence of the latter in the community.

Arthritis as a rare extra-intestinal manifestation of acute sigmoid diverticulitis

BACKGROUND

A causal association between acute diverticulitis of the sigmoid colon and arthritis has rarely been reported.

CASE REPORT

We report the case of a 60-year-old patient who developed migrating arthritis of the knee and ankle during the recurring episode of acute diverticulitis of the sigmoid colon. Treatment with NSAIDs and antibiotics had little effect on joint disease, but medical treatment was successful in reducing the diverticulitis-related symptoms. Arthritis promptly improved after surgical resection of the sigmoid colon, and 30 months later the patient is free of symptoms in the previously affected joints.

CONCLUSIONS

Five cases of diverticulitis-associated arthritis have been reported. The similar case reported here reconfirms that joint disease has a limited response to medical approaches. Colon resection is recommended for patients with diverticulitis-associated arthritis which does not respond promptly to antibiotic therapy.

Serum antibodies to group A streptococcal extracellular and cell-associated antigens in Egyptians with post-streptococcal diseases

We investigated serum antibodies to a comprehensive array of group A streptococcal antigens and superantigens in Egyptian subjects. Antibodies to Streptococcus pyogenes cell-associated proteins and to proteins released by rapidly dividing S. pyogenes were compared in four patient groups with different post-streptococcal diseases and in healthy controls. Enzyme-linked immunosorbent assays showed that total Ig and IgG to extracellular antigens were significantly higher in patients with acute rheumatic fever (ARF) compared to healthy controls, but no differences were found in either total Ig or IgG titres to cell-associated proteins between any of the groups. Western blotting showed that multiple extracellular and cell-associated antigens, covering a wide range of molecular masses, were recognised by all sera, including healthy controls. No evidence was obtained for putative dominant antigens associated with any disease group, although a low molecular mass cell-associated protein (approximately 4 kDa) was clearly recognised by two-thirds of subjects irrespective of disease status. These findings demonstrate that raised serum Ig and IgG titres to extracellular, but not cell-associated, S. pyogenes antigens are a feature of ARF in this population, and suggest that multiple S. pyogenes antigens contribute to this response.

Oxygen free radicals in children with acute rheumatic fever

We have investigated the relationship between oxygen free radicals and acute rheumatic fever with regard to diagnosis of the disease process. At the time of diagnosis, we measured the levels of reactive oxygen molecules in the plasma, this being a parameter for oxygen free radicals, and discovered the levels to be significantly higher when compared with those measured in a control group (P<0.05). The levels measured in the plasma, however, were not statistically different among patients with and without carditis. We found a progressive decrease in the levels measured in the plasma when patients with acute rheumatic fever were tested on the 15th, 30th and 90th days subsequent to diagnosis. By the 90th day, levels measured in the plasma were still higher, but no longer significantly elevated, when compared with the control group. The present study is preliminary, but raises the possibility that measurement of oxygen free radicals in the plasma could be used as a laboratory test for active state of acute rheumatic fever. Further investigations will be needed, nonetheless, to determine the clinical application of this technique.

Antibodies to streptococcal surface enolase react with human alpha-enolase: implications in poststreptococcal sequelae

The pathogenic mechanisms for developing acute rheumatic fever after group A streptococcal pharyngitis are still poorly understood. The glycolytic enzyme enolase is one of the major proteins on the surface of group A streptococci. Herein, significant cross-reactivity was shown between streptococcal enolase and human enolase. Fluorocytometric analysis revealed that antistreptococcal enolase antibodies react with the enolase expressed on the surface of hematopoietic cells. Furthermore, the enolase on the leukocyte surface was found to be up-regulated by inflammatory stimuli. Evaluation of antibody titers indicated that serum samples from patients with acute rheumatic fever have higher levels of antibodies that react with the human and bacterial enolases than do serum samples from patients with streptococcal pharyngitis or healthy control subjects. These results show that streptococcal enolase is a novel cross-reactive antigen that may play an important role in the initiation of the autoimmune diseases related to streptococcal infection.

Reactivity of rheumatic fever and scarlet fever patients' sera with group A streptococcal M protein, cardiac myosin, and cardiac tropomyosin: a retrospective study

Archived sera (collected in 1946) from acute rheumatic fever (ARF) and untreated scarlet fever and/or pharyngitis patients were reacted with streptococcal M protein, cardiac myosin, and cardiac tropomyosin. Except for very low levels to tropomyosin, antibodies to other antigens were not elevated in the sera of ARF patients relative to those of non-ARF patients, even though there was roughly equivalent exposure to group A streptococci. This suggests that antibodies to these molecules may not play a central role in the induction of ARF.

Short-course antibiotic treatment of 4782 culture-proven cases of group A streptococcal tonsillopharyngitis and incidence of poststreptococcal sequelae

A large-scale study with a 1-year follow-up was performed to compare 10 days of penicillin V with a short-course treatment (5 days) of other oral antibiotics in the treatment of group A beta-hemolytic streptococcus (GABHS) tonsillopharyngitis, to evaluate the efficacy and the incidence of poststreptococcal sequelae. The clinical response rates after completion of therapy were 94.5% in the 5-day group and 93.4% in the penicillin group (P<.001, equivalence test). The GABHS eradication rates were 83.3% in the 5-day group and 84.4% in the penicillin group (P=.022, equivalence test). Poststreptococcal sequelae were rare (5 patients) and did not occur in the context of this study. The efficacy of 5-day antibiotic regimens was equivalent to 10 days of penicillin V, but resolution of clinical symptoms was faster in the 5-day group (P<.001, Fisher's exact test). Recurrent tonsillopharyngitis occurs more frequently after treatment with penicillin (P=.03, Fisher's exact test).

Pathogenesis of group A streptococcal infections

Group A streptococci are model extracellular gram-positive pathogens responsible for pharyngitis, impetigo, rheumatic fever, and acute glomerulonephritis. A resurgence of invasive streptococcal diseases and rheumatic fever has appeared in outbreaks over the past 10 years, with a predominant M1 serotype as well as others identified with the outbreaks. emm (M protein) gene sequencing has changed serotyping, and new virulence genes and new virulence regulatory networks have been defined. The emm gene superfamily has expanded to include antiphagocytic molecules and immunoglobulin-binding proteins with common structural features. At least nine superantigens have been characterized, all of which may contribute to toxic streptococcal syndrome. An emerging theme is the dichotomy between skin and throat strains in their epidemiology and genetic makeup. Eleven adhesins have been reported, and surface plasmin-binding proteins have been defined. The strong resistance of the group A streptococcus to phagocytosis is related to factor H and fibrinogen binding by M protein and to disarming complement component C5a by the C5a peptidase. Molecular mimicry appears to play a role in autoimmune mechanisms involved in rheumatic fever, while nephritis strain-associated proteins may lead to immune-mediated acute glomerulonephritis. Vaccine strategies have focused on recombinant M protein and C5a peptidase vaccines, and mucosal vaccine delivery systems are under investigation.

Poststreptococcal reactive arthritis: clinical course and outcome in 15 patients

Patients with Group A beta-hemolytic streptococcal infection and articular disease, who do not fulfill the modified Jones criteria for diagnosis of acute rheumatic fever (ARF), have been classified as having poststreptococcal reactive arthritis (PSRA). We reviewed the clinical characteristics, laboratory findings and outcome of 15 patients with PSRA. None of these patients had clinical evidence of carditis. The pattern of joint involvement was variable and included arthritis in five patients and arthralgia in the remaining ten patients. Nine patients were treated with salicylates for one to 16 weeks; the others recovered spontaneously. Usually, the patients with arthralgia responded promptly to salicylates, while the response was poor in patients with arthritis. One patient with monoarthritis developed carditis nine months after his first arthritis attack. Another patient presenting with monoarthritis later had two additional episodes of poststreptococcal reactive arthralgia. It seems there is a wide spectrum of poststreptococcal rheumatic diseases, and patients with PSRA are also at risk for cardiac disease; therefore, prophylactic antibiotic therapy should be considered in these patients.

Diagnosis of rheumatic fever: current status of Jones Criteria and role of echocardiography

The original Jones Criteria as proposed by Dr. T. Duckett Jones have been modified four times and the updated revised criteria were published in 1992. According to this latest publication major manifestations are carditis, polyarthritis, chorea, erythema marginatum and subcutaneous nodules. Minor manifestations include fever, arthralgia and laboratory findings of elevated erythrocyte sedimentation rate, C-reactive protein and prolonged PR interval on ECG. For making a diagnosis of acute rheumatic fever, two major, or one major and two minor manifestations must be accompanied by supporting evidence of antecedent group A streptococcal infection in the form of positive throat culture or elevated or rising anti-streptolysin titre. The updated guidelines also highlighted a subgroup of "exceptions to Jones Criteria" for patients with chorea, indolent carditis and previous history of rheumatic fever or "rheumatic heart disease". Role of echocardiography has not been defined in these modifications but may be important, as clinical detection of soft murmurs may be difficult due to tachycardia. Doppler and color flow mapping is more sensitive in picking up minor digress of valvular regurgitation. Several studies have confirmed that the yield of carditis with valvular regurgitation increased with use of echocardiography in patients with acute rheumatic fever. Also echocardiography is of great help in mixed valve lesions to determine the severity of each lesion. Other abnormalities detected on echocardiography in acute carditis include prolapse of the valve, focal nodular thickening of leaflets and pericardial effusion. Jones Criteria are guidelines to assist the physician and should not be substituted for clinical judgement as strictly following them may result in underdiagnosis of this disease in our country.

Further observations and characterization of monoclonal antibodies reacting with B cell alloantigens associated with rheumatic fever and rheumatic heart disease

Elevated levels of B lymphocytes with a unique surface alloantigen have been reported to be characteristic of patients with acute rheumatic fever or rheumatic heart disease. Mouse monoclonal antibodies (mAbs) to this alloantigen have been proposed as being useful in identifying individuals at risk for the development of these sequelae of group A streptococcal infection. However, previous studies have suggested that the discriminating ability of the mAbs was highest when the mAbs were made by using lymphocytes from the same ethnic population. To confirm and extend this observation, additional mouse mAbs were developed and their properties defined. These three mAbs-PG-12A, PG-13A, and PG-20A-reacted with B cells from more than 90% of North Indian patients with acute rheumatic fever or rheumatic heart disease. Each of these three new mAbs identified the highest levels of reactive B cells in patients with active acute rheumatic fever. Lower levels of positive reacting lymphocytes were found in individuals with quiescent chronic rheumatic heart disease, and markedly reduced percentages of reactive cells were observed in normal control subjects. The proportion of reactive lymphocytes in individual patients varied according to which of the three was tested, suggesting the possibility of a spectrum of "rheumatic" epitopes in susceptible individuals. The data further suggested that enhanced discriminatory ability for identifying "at-risk" susceptible patients could be obtained by testing with a combination of mAbs. If reduction in the incidence of acute rheumatic fever can be facilitated by early identification of susceptible individuals, accurate and sensitive detection of a marker antigen would result in more cost-effective public health measures. Additional population studies are required to more precisely define and confirm these detection techniques.

Comparison of short-course (5 day) cefuroxime axetil with a standard 10 day oral penicillin V regimen in the treatment of tonsillopharyngitis

Oral penicillin V given three times daily in doses of 50,000-100,000 IU daily has been the standard treatment for tonsillopharyngitis for the last few decades. These regimens, initially recommended by the American Heart Association, were extrapolated from i.v. dosing with long-acting forms of penicillin which had been shown to prevent post-streptococcal sequelae. More recently, several antibiotics, including cefuroxime axetil, have been shown to be at least as effective as penicillin G in eradicating group A beta-haemolytic streptococci (GABHS) but their influence on post-streptococcal sequelae has never been assessed in a large-scale trial. The German Society for Pediatric Infectious Diseases (DGPI) undertook a large study of culture-proven tonsillopharyngitis involving several agents and included a 1 year follow-up to establish the effect on sequelae. In one arm of this study, cefuroxime 250 mg bid was compared with 50,000 IU penicillin V given in three divided doses. Cefuroxime axetil was more effective than oral penicillin V in eradicating GABHS at the assessment 2-4 days post-treatment (441/490 (90%) patients versus 1196/1422 (84%) patients; P = 0.001). Clinically, the two agents were equivalent in efficacy, and carriage rates were similar (11.1% and 13.8%, respectively) in patients receiving cefuroxime axetil and penicillin V, 7-8 weeks post-treatment. One case of glomerular nephritis occurred in a patient given penicillin V. There were no post-streptococcal sequelae confirmed for patients treated with cefuroxime axetil. The findings confirm the previously reported efficacy of short-course (4-5 day) treatments with cefuroxime axetil and indicate that short-course treatment is comparable to the standard oral penicillin V regimen in preventing post-streptococcal sequelae.

Familial Mediterranean fever and acute rheumatic fever: a pathogenetic relationship?

The frequency of acute rheumatic fever (ARF) in patients with familial Mediterranean fever (FMF) was documented and the effects of preceding streptococcal infections on the exacerbation of FMF were determined. In the first part of the study, 162 individuals with FMF were investigated for a history of ARF in a retrospective study. In the second part of the study, antistreptolysin-O (ASO) titres were measured in 130 individuals with FMF. Thirty-six patients had an arthritic attack (group A1), 55 patients had a typical FMF attack without arthritis (group A2) and 39 patients were in the attack-free interval (group B) during the investigation. Nine patients with FMF (5.5%) were considered to have ARF and three of them (1.85%) also had rheumatic heart disease. This prevalence of rheumatic heart disease in FMF is higher than that of the normal population (0.65%) reported in Turkey. Elevated ASO titres were found in 75%, 42% and 38% of the patients in groups A1, A2 and B, respectively. These percentages were found to be significantly higher in group A1 than in both groups A2 (p<0.01) and B (p<0.01). We concluded that patients with FMF might be more prone to the late complications of streptococcal infections.

Current guidelines for the treatment of patients with rheumatic fever

Rheumatic fever is a multisystem inflammatory disease that occurs as a delayed sequelae to group A streptococcal pharyngitis. The important clinical manifestations are migratory polyarthritis, carditis, chorea, subcutaneous nodules and erythema marginatum occurring in varying combinations. The pathogenesis of this disorder remains elusive: an antigenic mimicry hypothesis best explains the affliction of various organ systems after a lag period following pharyngeal infection. In its classic milder form, the disorder is largely self-limited and resolves without sequelae, but carditis may be fatal in severe forms of the disease. Chronic and progressive damage to the heart valves leads to the most important public health manifestations of the disease. Anti-inflammatory agents provide dramatic clinical improvement, but do not prevent the subsequent development of rheumatic heart disease. The role of corticosteroids in treatment of carditis is uncertain and controlled studies have failed to demonstrate improved long term prognosis. Chorea, once considered a benign self-limited disease, is now felt to require more aggressive treatment, in particular with sedatives. Prevention of first and subsequent attacks of rheumatic fever is the mainstay in the limited arsenal available to alter the natural history of this disease.

Superantigen-induced T cell responses in acute rheumatic fever and chronic rheumatic heart disease patients

CD4+ and CD8+ T cells from healthy donors, acute rheumatic fever (ARF) and chronic rheumatic heart disease (CRHD) patients responded variably to a superantigen from Streptococcus pyogenes--Streptococcal pyrogenic erythrogenic toxin A (SPE-A). In vitro culture of CD4+ T cells from ARF patients (CD4-ARF) with SPE-A exhibited a Th1 type of response as they produced high levels of IL-2, while CD4+ T cells from CRHD patients (CD4-RHD) secreted IL-4 and IL-10 in large amounts, i.e. Th2 type of cytokine profile. The skewing of human CD4+ T cells (in response to SPE-A stimulation) to Th1 or Th2 type reflects the role of the two subsets in a disorder with differing intensities at the two extremes of the spectrum. Moreover, the anergy induction experiments revealed that CD8-ARF and CD8-RHD undergo anergy (to different extents), whereas CD4+ T cells do not, in response to re-stimulation by SPE-A. These results initially demonstrate that both CD4+ and CD8+ T cells respond differentially to SPE-A, and hence it is an important observation with respect to the pathogenesis of ARF/CRHD. Anergy in CD8+ T cells in the presence of SPE-A in vitro goes a step further to show the clinical relevance of these cells and their possible role in suppression of the disease.