Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in northern Thailand

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.

Risk Factors for Acute Rheumatic Fever: Literature Review and Protocol for a Case-Control Study in New Zealand

Acute rheumatic fever (ARF) and its sequela, rheumatic heart disease (RHD), have largely disappeared from high-income countries. However, in New Zealand (NZ), rates remain unacceptably high in indigenous Māori and Pacific populations. The goal of this study is to identify potentially modifiable risk factors for ARF to support effective disease prevention policies and programmes. A case-control design is used. Cases are those meeting the standard NZ case-definition for ARF, recruited within four weeks of hospitalisation for a first episode of ARF, aged less than 20 years, and residing in the North Island of NZ. This study aims to recruit at least 120 cases and 360 controls matched by age, ethnicity, gender, deprivation, district, and time period. For data collection, a comprehensive pre-tested questionnaire focussed on exposures during the four weeks prior to illness or interview will be used. Linked data include previous hospitalisations, dental records, and school characteristics. Specimen collection includes a throat swab (Group A Streptococcus), a nasal swab (Staphylococcus aureus), blood (vitamin D, ferritin, DNA for genetic testing, immune-profiling), and head hair (nicotine). A major strength of this study is its comprehensive focus covering organism, host and environmental factors. Having closely matched controls enables the examination of a wide range of specific environmental risk factors.

In silico characterisation of the two-component system regulators of Streptococcus pyogenes

Bacteria respond to environmental changes through the co-ordinated regulation of gene expression, often mediated by two-component regulatory systems (TCS). Group A Streptococcus (GAS), a bacterium which infects multiple human body sites and causes multiple diseases, possesses up to 14 TCS. In this study we examined genetic variation in the coding sequences and non-coding DNA upstream of these TCS as a method for evaluating relationships between different GAS emm-types, and potential associations with GAS disease. Twelve of the 14 TCS were present in 90% of the genomes examined. The length of the intergenic regions (IGRs) upstream of TCS coding regions varied from 39 to 345 nucleotides, with an average nucleotide diversity of 0.0064. Overall, IGR allelic variation was generally conserved with an emm-type. Subsequent phylogenetic analysis of concatenated sequences based on all TCS IGR sequences grouped genomes of the same emm-type together. However grouping with emm-pattern and emm-cluster-types was much weaker, suggesting epidemiological and functional properties associated with the latter are not due to evolutionary relatedness of emm-types. All emm5, emm6 and most of the emm18 genomes, all historically considered rheumatogenic emm-types clustered together, suggesting a shared evolutionary history. However emm1, emm3 and several emm18 genomes did not cluster within this group. These latter emm18 isolates were epidemiologically distinct from other emm18 genomes in study, providing evidence for local variation. emm-types associated with invasive disease or nephritogenicity also did not cluster together. Considering the TCS coding sequences (cds), correlation with emm-type was weaker than for the IGRs, and no strong correlation with disease was observed. Deletion of the malate transporter, maeP, was identified that serves as a putative marker for the emm89.0 subtype, which has been implicated in invasive outbreaks. A recombination-related, subclade-forming DNA motif was identified in the putative receiver domain of the Spy1556 response regulator that correlated with throat-associated emm-pattern-type A-C strains.

M protein gene (emm type) analysis of group A Streptococcus isolates recovered during an acute glomerulonephritis outbreak in northern Western Australia

Certain M protein types of group A streptococcus (GAS) are known to cause acute post-streptococcal glomerulonephritis (APSGN). Outbreaks of APSGN can occur regularly in tropical regions but the emm types responsible are geographically and temporally diverse. GAS isolates from Western Australia (WA) were analysed for emm type and emm cluster during the period of increased APSGN activity in the tropical northern Kimberley region of WA. Although emm types 49, 75 and 108 and corresponding emm clusters E3, E6 and D4 were more common in WA during the outbreak there was no predominant circulating emm type or cluster found to correspond to the APSGN activity. This is consistent with the high diversity of GAS strains found during APSGN outbreaks in other countries. Potential vaccine coverage of the new 30-valent M-protein GAS vaccine was 70%.

Correlation between PFGE Groups and mrp/epf/sly Genotypes of Human Streptococcus suis Serotype 2 in Northern Thailand

Streptococcus suis infection is a severe zoonotic disease commonly found in Northern Thailand where people often consume raw pork and/or pig's blood. The most frequent clinical presentations are meningitis, sepsis, and endocarditis with higher rate of mortality and hearing loss sequelae. To clarify the correlation between pulsed-field gel electrophoresis (PFGE) groups and mrp/epf/sly genotypes of S. suis serotype 2, 62 patient and 4 healthy pig isolates from Northern Thailand were studied. By PFGE analysis, at 66% homology, most human isolates (69.4%) and 1 pig isolate were in group A, whereas 14.5% of human isolates and 3 out of 4 pig isolates were in group D. According to mrp/epf/sly genotypes, 80.6% of human isolates were identified in mrp⁺epf⁻sly⁻ and only 12.9% were in mrp⁻epf⁻sly⁺ genotypes; in contrast, 1 and 3 pig isolates were detected in these two genotypes, respectively. Interestingly, all isolates of S. suis serotype 2 classified in PFGE groups A, B, and E were set in mrp⁺epf⁻sly⁻ genotypes. These data show a close correlation between PFGE groups and mrp/epf/sly genotypes of human S. suis serotype 2.

Prevalence of Group A beta-haemolytic Streptococcus isolated from children with acute pharyngotonsillitis in Aden, Yemen

OBJECTIVES

To estimate the prevalence of Group A beta-haemolytic streptococcus (GAS) and non-GAS infections among children with acute pharyngotonsillitis in Aden, Yemen, to evaluate the value of a rapid diagnostic test and the McIsaac score for patient management in this setting and to determine the occurrence of emm genotypes among a subset of GAS isolated from children with acute pharyngotonsillitis and a history of acute rheumatic fever (ARF) or rheumatic heart disease (RHD).

METHODS

Group A beta-haemolytic streptococcus infections in school-aged children with acute pharyngotonsillitis in Aden, Yemen, were diagnosed by a rapid GAS antigen detection test (RADT) and/or GAS culture from a throat swab. The RADT value and the McIsaac screening score for patient management were evaluated. The emm genotype of a subset of GAS isolates was determined.

RESULTS

Group A beta-haemolytic streptococcus pharyngotonsillitis was diagnosed in 287/691 (41.5%; 95% CI 37.8-45.3) children. Group B, Group C and Group G beta-haemolytic streptococci were isolated from 4.3% children. The RADT had a sensitivity of 238/258 (92.2%) and specificity of 404/423 (95.5%) against GAS culture. A McIsaac score of ≥4 had a sensitivity of 93% and a specificity of 82% for confirmed GAS infection. The emm genotypes in 21 GAS isolates from children with pharyngitis and a history of ARF and confirmed RHD were emm87 (11), emm12 (6), emm28 (3) and emm5 (1).

CONCLUSION

This study demonstrates a very high prevalence of GAS infections in Yemeni children and the value of the RADT and the McIsaac score in this setting. More extensive emm genotyping is necessary to understand the local epidemiology of circulating strains.

Evolution of the capsular operon of Streptococcus iniae in response to vaccination

Streptococcus iniae causes severe septicemia and meningitis in farmed fish and is also occasionally zoonotic. Vaccination against S. iniae is problematic, with frequent breakdown of protection in vaccinated fish. The major protective antigens in S. iniae are the polysaccharides of the capsule, which are essential for virulence. Capsular biosynthesis is driven and regulated by a 21-kb operon comprising up to 20 genes. In a long-term study, we have sequenced the capsular operon of strains that have been used in autogenous vaccines across Australia and compared it with the capsular operon sequences of strains subsequently isolated from infected vaccinated fish. Intriguingly, strains isolated from vaccinated fish that subsequently become infected have coding mutations that are confined to a limited number of genes in the cps operon, with the remainder of the genes in the operon remaining stable. Mutations in strains in diseased vaccinated fish occur in key genes in the capsular operon that are associated with polysaccharide configuration (cpsG) and with regulation of biosynthesis (cpsD and cpsE). This, along with high ratios of nonsynonymous to synonymous mutations within the cps genes, suggests that immune response directed predominantly against capsular polysaccharide may be driving evolution in a very specific set of genes in the operon. From these data, it may be possible to design a simple polyvalent vaccine with a greater operational life span than the current monovalent killed bacterins.

Rheumatic heart disease

Rheumatic heart disease, often neglected by media and policy makers, is a major burden in developing countries where it causes most of the cardiovascular morbidity and mortality in young people, leading to about 250,000 deaths per year worldwide. The disease results from an abnormal autoimmune response to a group A streptococcal infection in a genetically susceptible host. Acute rheumatic fever--the precursor to rheumatic heart disease--can affect different organs and lead to irreversible valve damage and heart failure. Although penicillin is effective in the prevention of the disease, treatment of advanced stages uses up a vast amount of resources, which makes disease management especially challenging in emerging nations. Guidelines have therefore emphasised antibiotic prophylaxis against recurrent episodes of acute rheumatic fever, which seems feasible and cost effective. Early detection and targeted treatment might be possible if populations at risk for rheumatic heart disease in endemic areas are screened. In this setting, active surveillance with echocardiography-based screening might become very important.

Atypical bacteria in adenoids and tonsils of children requiring adenotonsillectomy

CONCLUSIONS

The results of this study suggest that atypical bacteria may be involved not only in acute upper airway diseases but also in recurrent infections requiring adenoidectomy and/or tonsillectomy. Therefore, their identification, followed by an appropriate treatment, should be considered.

OBJECTIVE

Although viruses and group A beta-haemolytic streptococci (GABHS) represent the most frequent bacterial aetiological agents of paediatric upper respiratory tract infections (URTIs), chlamydia and Mycoplasma pneumoniae have also been found in acute tonsillopharyngitis. Nevertheless their relevance in chronic or recurrent URTI has never been evaluated. This study aimed to further address the role of atypical bacteria in recurrent URTIs requiring adenoidectomy and tonsillectomy.

METHODS

Samples from 55 consecutive children who underwent adenoidectomy and/or tonsillectomy for recurrent or chronic URTI were cut transversely into smaller sections of 5 mm. Each section was pooled and assayed by specific PCR for viruses and bacteria.

RESULTS

Adenovirus was detected in 10 patients (18.2%), influenza A virus in one patient and influenza B virus in another. None of the other tested viruses was found. GABHS was found in 37 patients (67.3%). Moraxella catarrhalis and Haemophilus influenzae were detected in 30 patients (54.5%). M. pneumoniae was detected in 6 patients (10.9%) and C. pneumoniae was found in 10 patients (18.2%).

Group A streptococcal genotypes from throat and skin isolates in the United Arab Emirates

Background

The bacterium Streptococcus pyogenes causes a variety of human diseases that range from relatively mild skin infections to severe invasive diseases, such as acute rheumatic fever, glomerulonephritis, puerperal sepsis, necrotizing fasciitis, meningitis, and streptococcal toxic shock syndrome. Accurate identification and typing of group A hemolytic streptococci (GAS) is essential for epidemiological and pathogenetic studies of streptococcal diseases. For this reason, The genetic diversity of group A streptococcal (GAS) isolates from subjects in the United Arab Emirates with streptococcal disease was studied using emm gene sequence analysis. The emm typing system which is based on sequence analysis of PCR products of the N-terminal hypervariable region of the M protein gene, concurs with M serotyping almost 1:1.

Findings

A total of 38 GAS isolates were analyzed, including 35 isolates from throat and 3 from skin. Among the 38 isolates, a total of 25 different emm/st types were detected: 20 isolates (53%) belonged to 16 validated standard reference emm types and 18 isolates (47%) belonged to 9 recognized sequence types.

Conclusions

This is the first emm typing study in the United Arab Emirates to demonstrate the heterogeneity of the GAS population.

School-based prevention of acute rheumatic fever: a group randomized trial in New Zealand

BACKGROUND

Acute rheumatic fever (ARF) and its sequela, rheumatic heart disease is the commonest cause of childhood cardiac morbidity globally. The current approach to the prevention of a primary attack of rheumatic fever in children using oral medication for streptococcal pharyngitis is poorly supported. The efficacy of injectable penicillin, in high rheumatic fever incidence military environments is indisputable.

OBJECTIVE

To evaluate school-based control of rheumatic fever in an endemic area.

METHODS

Fifty-three schools ( approximately 22,000 students) from a rheumatic fever high incidence setting ( approximately 60/100,000) in Auckland, New Zealand were randomized. The control group received routine general practice care. The intervention was a school-based sore throat clinic program with free nurse-observed oral penicillin treatment of group A streptococcal pharyngitis. The outcome measure was ARF in any child attending a study school. Analysis A defined ARF cases using criteria derived from Jones Criteria 1965 (definite) and 1956 (probable) with more precise definitions. Analysis B was based on 1992 Jones criteria but also included echocardiography to determine definite cases.

RESULTS

In Analysis A, 24 (55/100,000) cases occurred in clinic schools and 29 (67/100,000) in nonclinic schools, a 21% reduction when adjusted for demography and study design (P = 0.47). Analysis B revealed a 28% reduction 26 (59/100,000) and 33 (77/100,000) cases, respectively (P = 0.27).

CONCLUSION

This study involving 86,874 person-years showed a nonsignificant reduction in the school-based sore throat clinic programs.

Host-directed evolution of a novel lactate oxidase in Streptococcus iniae isolates from barramundi (Lates calcarifer)

In Streptococcus iniae, lactate metabolism is dependent upon two proteins, lactate permease that mediates uptake and lactate oxidase, a flavin mononucleotide-dependent enzyme that catalyzes oxidation of alpha-hydroxyacids. A novel variant of the lactate oxidase gene, lctO, in Australian isolates of S. iniae from diseased barramundi was found during a diagnostic screen using LOX-1 and LOX-2 primers, yielding amplicons of 920 bp instead of the expected 869 bp. Sequencing of the novel gene variant (type 2) revealed a 51-nucleotide insertion in lctO, resulting in a 17-amino-acid repeat in the gene product, and three-dimensional modeling indicated formation of an extra loop in the monomeric protein structure. The activities of the lactate oxidase enzyme variants expressed in Escherichia coli were examined, indicating that the higher-molecular-weight type 2 enzyme exhibited higher activity. Growth rates of S. iniae expressing the novel type 2 enzyme were not reduced at lactate concentrations of 0.3% and 0.5%, whereas a strain expressing the type 1 enzyme exhibited reduced growth rates at these lactate concentrations. During a retrospective screen of 105 isolates of S. iniae from Australia, the United States, Canada, Israel, Réunion Island, and Thailand, the type 2 variant arose only in isolates from a single marine farm with unusually high tidal flow in the Northern Territory, Australia. Elevated plasma lactate levels in the fish, resulting from the effort of swimming in tidal flows of up to 3 knots, may exert sufficient selective pressure to maintain the novel, high-molecular-weight enzyme variant.

Characterization of emm types and superantigens of Streptococcus pyogenes isolates from children during two sampling periods

The characteristics of 359 group A streptococcal (GAS) isolates collected from Chinese paediatric patients in two periods (1993-1994, 2005-2006) were studied. Isolates were assigned to emm types and assayed for eight superantigen (SAg) genes (speA, speC, speH, speI, speG, speJ, ssa, SMEZ). Types emm1 and emm12 were consistently the most prevalent during the two periods, while others varied in frequency. GAS isolates carrying six or more SAg genes increased from 46.53% (1993-1994) to 78.39% (2005-2006); ssa, speH and speJ genes (P<0.05) increased but speA declined (P<0.05). SAg gene profiles were closely associated with the emm type, but strains of the same emm type sometimes carried different SAg genes in the two periods. No significant difference in emm-type distribution and SAg gene profile was noted between isolates from different diseases. These data may contribute towards the development of a GAS vaccine in China.

Identification and molecular characterisation of a fibrinogen binding protein from Streptococcus iniae

Background

Binding of serum components by surface M-related proteins, encoded by the emm genes, in streptococci constitutes a major virulence factor in this important group of organisms. The present study demonstrates fibrinogen binding by S. iniae, a Lancefield non-typeable pathogen causing devastating fish losses in the aquaculture industry and an opportunistic pathogen of humans, and identifies the proteins involved and their encoding genes.

Results

Fibrinogen binding by S. iniae significantly reduced respiratory burst activity of barramundi peritoneal macrophages in primary cultures compared to BSA-treated or untreated controls, indicating a potentially important role for fibrinogen binding cell-surface proteins in avoiding phagocytic attack in fish. We describe a novel emm-like gene, simA, encoding a 57 kDa fibrinogen binding M-like protein in S. iniae. These SiM proteins and their corresponding tetrameric structures from some sequevar types (~230 kDa) bound fibrinogen in Western blots. simA was most closely related (32% identity) to the demA gene of S. dysgalactiae. Genome walking and sequencing determined the genetic organization of the simA region had similarities to the mgrC regulon in GCS and to S. uberis. Moreover, a putative multigene regulator, mgx was orientated in the opposite direction to the simA gene in common with S. uberis, but contrary to findings in GAS and GCS. In GAS, diversity among emm-genes and consequent diversity of their M-related proteins results in substantial antigenic variation. However, an extensive survey of S. iniae isolates from diverse geographic regions and hosts revealed only three variants of the gene, with one sequevar accounting for all but two of the 50 isolates analysed.

Conclusion

These proteins play a role in avoiding oxidative attack by phagocytic cells during infection of fish by S. iniae, but genetic diversity amongst these key surface proteins has not yet arisen. This lack of diversity coupled with a functional role in macrophage resistance suggests that these proteins may constitute important targets for future vaccines against S. iniae in fish.

Current status of group A streptococcal vaccine development

We now have a much more detailed understanding of the molecular pathogenesis of GAS infections. These discoveries have led to the identification of several vaccine candidates which are in various stages of development. One of the leading candidate antigens is the surface M protein, which confers protection against infection in animal models. In addition, M antibodies in human serum correlate with protection against infection with the homologous serotype of GAS. Molecular techniques have been used to genetically engineer highly complex multivalent M protein-based vaccines that appear to be free of potentially harmful tissue crossreactive epitopes. A 26-valent vaccine has been shown to be well-tolerated and immunogenic in adult volunteers and is now being considered for pediatric trials, which is the primary target group for the vaccine. Ongoing efforts are now addressing the epidemiology of GAS infections in developing countries so that new vaccines can be designed to prevent the infections that may trigger ARF and RHD. Successful deployment of safe and effective vaccines to prevent GAS infections and their complications could potentially have a significant impact on the health of millions of people around the world.

The dynamic nature of group A streptococcal epidemiology in tropical communities with high rates of rheumatic heart disease

Prospective surveillance was conducted in three remote Aboriginal communities with high rates of rheumatic heart disease in order to investigate the epidemiology of group A beta-haemolytic streptococci (GAS). At each household visit, participants were asked about sore throat. Swabs were taken from all throats and any skin sores. GAS isolates were emm sequence and pattern-typed using standard laboratory methods. There were 531 household visits; 43 different emm types and subtypes (emmST) were recovered. Four epidemiological patterns were observed. Multiple emmST were present in the population at any one time and household acquisition rates were high. Household acquisition was most commonly via 5- to 9-year-olds. Following acquisition, there was a 1 in 5 chance of secondary detection in the household. Throat detection of emmST was brief, usually <2 months. The epidemiology of GAS in these remote Aboriginal communities is a highly dynamic process characterized by emmST diversity and turnover.

Bactericidal activity of M protein conserved region antibodies against group A streptococcal isolates from the Northern Thai population

Background

Most group A streptococcal (GAS) vaccine strategies have focused on the surface M protein, a major virulence factor of GAS. The amino-terminus of the M protein elicits antibodies, that are both opsonic and protective, but which are type specific. J14, a chimeric peptide that contains 14 amino acids from the M protein conserved C-region at the carboxy-terminus, offers the possibility of a vaccine which will elicit protective opsonic antibodies against multiple different GAS strains. In this study, we searched for J14 and J14-like sequences and the number of their repeats in the C-region of the M protein from GAS strains isolated from the Northern Thai population. Then, we examined the bactericidal activity of J14, J14.1, J14-R1 and J14-R2 antisera against multiple Thai GAS strains.

Results

The emm genes of GAS isolates were sequenced and grouped as 14 different J14-types. The most diversity of J14-types was found in the C1-repeat. The J14.1 type was the major sequence in the C2 and C3-repeats. We have shown that antisera raised against the M protein conserved C-repeat region peptides, J14, J14.1, J14-R1 and J14-R2, commonly found in GAS isolates from the Northern Thai population, are able to kill GAS of multiple different emm types derived from an endemic area. The mean percent of bactericidal activities for all J14 and J14-like peptide antisera against GAS isolates were more than 70%. The mean percent of bactericidal activity was highest for J14 antisera followed by J14-R2, J14.1 and J14-R1 antisera.

Conclusion

Our study demonstrated that antisera raised against the M protein conserved C-repeat region are able to kill multiple different strains of GAS isolated from the Northern Thai population. Therefore, the four conserved "J14" peptides have the potential to be used as GAS vaccine candidates to prevent streptococcal infections in an endemic area.

High diversity of group A streptococcal emm types among healthy schoolchildren in Ethiopia

BACKGROUND

Although the prevalence of rheumatic heart disease in Ethiopia is one of the highest in the world, the epidemiology of group A streptococci (GAS) in this country is little known. GAS typing is a hallmark of both the epidemiology and understanding of diseases caused by these organisms. We have therefore conducted this study to investigate the emm (M-protein gene) type distribution of GAS carriers among Ethiopian schoolchildren.

METHODS

In the present study, we performed emm typing of 82 GAS isolates collected from the throats of healthy schoolchildren (6-14 years of age) residing in 3 different urban sites in Ethiopia: Addis Ababa, Gondar, and Dire Dawa.

RESULTS

We report high diversity of GAS isolates recovered from healthy schoolchildren. Eighty-two isolates represented 43 different sequence types. Thirteen newly described subtypes were detected in this study. Of the emm types prevalent in the study communities, 46% were not included in the 26-valent GAS vaccine.

CONCLUSIONS

The high diversity of emm types encountered within 3 months of collection suggest that production of a vaccine candidate based on the M-protein amino termini appears to be impractical for this population. We suggest that investigations of other vaccine candidates, including the C5a peptidase, GAS carbohydrate, and fibronectin-binding proteins, as well as conserved M-protein region vaccines, should be intensified to address the needs of this population.

M protein gene (emm type) analysis of group A beta-hemolytic streptococci from Ethiopia reveals unique patterns

The genetic diversity of group A streptococcal (GAS) isolates obtained in 1990 from Ethiopian children with various streptococcal diseases was studied by using emm gene sequence analysis. A total of 217 GAS isolates were included: 155 and 62 isolates from throat and skin, respectively. A total of 78 different emm/st types were detected among the 217 isolates. Of these, 166 (76.5%) belonged to 52 validated reference emm types, 26 (11.9%) belonged to 16 already recognized sequence types (st types) and 25 (11.5%) belonged to 10 undocumented new sequence types. Resistance to tetracycline (148 of 217) was not correlated to emm type. Isolation rate of the classical rheumatogenic and nephritogenic strains was low from cases of acute rheumatic fever (ARF) and acute glomerulonephritis (AGN), respectively. Instead, the recently discovered st types were overrepresented among isolates from patients with ARF (3 of 7) and AGN (9 of 16) (P < 0.01) compared to isolates from subjects with tonsillitis and from healthy carriers (10 of 57 and 16 of 90, respectively). In contrast to rheumatogenic strains from the temperate regions, more than half of the isolates from ARF (four of seven) carried the genetic marker for skin preference, emm pattern D, although most of them (six of seven) were isolated from throat. Of 57 tonsillitis-associated isolates, 16 (28%) belonged to emm pattern D compared to <1% in temperate regions. As in other reports emm patterns A to C were strongly associated with throat, whereas emm pattern D did not correlate to skin. This first large-scale emm typing report from Africa has demonstrated a heterogeneous GAS population and contrasting nature of GAS epidemiology in the region.

M protein typing of Thai group A streptococcal isolates by PCR-Restriction fragment length polymorphism analysis

BACKGROUND

Group A streptococcal (GAS) infections can lead to the development of severe post-infectious sequelae, such as rheumatic fever (RF) and rheumatic heart disease (RHD). RF and RHD are a major health concern in developing countries, and in indigenous populations of developed nations. The majority of GAS isolates are M protein-nontypeable (MNT) by standard serotyping. However, GAS typing is a necessary tool in the epidemiologically analysis of GAS and provides useful information for vaccine development. Although DNA sequencing is the most conclusive method for M protein typing, this is not a feasible approach especially in developing countries. To overcome this problem, we have developed a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-based assay for molecular typing the M protein gene (emm) of GAS.

RESULTS

Using one pair of primers, 13 known GAS M types showed one to four bands of PCR products and after digestion with Alu I, they gave different RFLP patterns. Of 106 GAS isolates examined from the normal Thai population and from patients with GAS-associated complications including RHD, 95 isolates gave RFLP patterns that corresponded to the 13 known M types. Only 11 isolates gave RFLP patterns that differed from the 13 known M types. These were then analyzed by DNA sequencing and six additional M types were identified. In addition, we found that M93 GAS was the most common M type in the population studied, and is consistent with a previous study of Thai GAS isolates.

CONCLUSION

PCR-RFLP analysis has the potential for the rapid screening of different GAS M types and is therefore considerably advantageous as an alternative M typing approach in developing countries in which GAS is endemic.

Acute rheumatic fever

Acute rheumatic fever (ARF) and its chronic sequela, rheumatic heart disease (RHD), have become rare in most affluent populations, but remain unchecked in developing countries and in some poor, mainly indigenous populations in wealthy countries. More than a century of research, mainly in North America and Europe, has improved our understanding of ARF and RHD. However, whether traditional views need to be updated in view of the epidemiological shift of the past 50 years is still to be established, and improved data from developing countries are needed. Doctors who work in populations with a high incidence of ARF are adapting existing diagnostic guidelines to increase their sensitivity. Group A streptococcal vaccines are still years away from being available and, even if the obstacles of serotype coverage and safety can be overcome, their cost could make them inaccessible to the populations that need them most. New approaches to primary prevention are needed given the limitations of primary prophylaxis as a population-based strategy. The most effective approach for control of ARF and RHD is secondary prophylaxis, which is best delivered as part of a coordinated control programme.

M protein conserved region antibodies opsonise multiple strains of Streptococcus pyogenes with sequence variations in C-repeats

The development of a group A streptococcal (GAS) vaccine has focused on the M protein, a major virulence factor. Antibodies against the amino terminal domain of the M protein are generally protective but only provide type-specific immunity. J14, a 29-mer peptide sequence which contains a conserved epitope from the C-repeat region of the M protein, offers the possibility of a vaccine which will elicit protective opsonic antibodies against multiple GAS strains. In this study we have shown that antibodies raised against J14 are capable of opsonising 37 GAS isolates representing different emm types derived from a region in which GAS infection is endemic. We also demonstrate that J14 antisera is capable of opsonising GAS isolates containing J14 homologues but not J14-specific sequences, further increasing the strain coverage of this vaccine candidate. Isolates with three C-repeats were opsonised more efficiently than isolates with two repeats. Opsonisation of a strain with only a single C-repeat was dramatically lower than other strains tested. The number of C-repeats present in the M protein of individual isolates therefore appears to be the critical factor in determining bactericidal capacity of J14 antisera. The reduced opsonic capacity of sera against this strain was shown to correlate with a reduced capacity to bind J14 antisera, as demonstrated by immunofluorescence microscopy and FACS analysis. In vivo challenge experiments also confirmed the protective efficacy of immunisation with J14 peptide.

High Diversity of Group A Streptococcal emm Types in an Indian Community: The Need to Tailor Multivalent Vaccines

BACKGROUND

Concern about the emergence of antibiotic-resistant strains and about morbidity and/or mortality related to rheumatic fever and rheumatic heart disease has been a continuous impetus for the development of a safe, effective vaccine against group A Streptococcus (GAS). To date, >120 GAS M types are known, as identified by serological typing. In general, serum immunoglobulin G directed to the hypervariable NH2 terminal portion of M protein leads to complement fixation and opsonophagocytosis of the homologous streptococcal serotype by polymorphonuclear leukocytes, and the protection is type specific. The sequence variation at the N terminus ultimately affects the binding of opsonic antibodies. Because of hypervariability in these opsonic sequences from different M types, it was relevant to use epitopes derived from these multiple sequences in a "multivalent vaccine" design for evaluation of protection against these M types of GAS. Thus, any attempts to design vaccines for a given community will require information on N terminal-sequence typing and variation.

METHODS

In the present study, we performed molecular characterization of isolates recovered from patients in northern India--to our knowledge, for the first time--in an attempt to study the circulating M types and their N terminal sequence variability.

RESULTS

We report tremendous diversity in GAS strains recovered from symptomatic patients, with implications on the design of appropriate vaccines. Fifty-nine isolates represented 33 different sequence types. Very few novel types and no predominant clones were found.

CONCLUSIONS

The high diversity of emm types encountered in a single year suggests that any M protein-based multivalent vaccine would have to be specifically tailored for this region.

Acute rheumatic fever: a chink in the chain that links the heart to the throat?

Acute rheumatic fever (ARF) remains a major problem in tropical regions, resource-poor countries, and minority indigenous communities. It has long been thought that group A streptococcal (GAS) pharyngitis alone was responsible for acute rheumatic fever; this belief has been supported by laboratory and epidemiological evidence gathered over more than 60 years, mainly in temperate climates where GAS skin infection is uncommon. GAS strains have been characterised as either rheumatogenic or nephritogenic based on phenotypic and genotypic properties. Primary prevention strategies and vaccine development have long been based on these concepts. The epidemiology of ARF in Aboriginal communities of central and northern Australia challenges this view with reported rates of ARF and rheumatic heart disease (RHD) that are among the highest in the world. GAS throat colonisation is uncommon, however, and symptomatic GAS pharyngitis is rare; pyoderma is the major manifestation of GAS infection. Typical rheumatogenic strains do not occur. Moreover, group C and G streptococci have been shown to exchange key virulence determinants with GAS and are more commonly isolated from the throats of Aboriginal children. We suggest that GAS pyoderma and/or non-GAS infections are driving forces behind ARF in these communities and other high-incidence settings. The question needs to be resolved as a matter of urgency because current approaches to controlling ARF/RHD in Aboriginal communities have clearly been ineffective. New understanding of the pathogenesis of ARF would have an immediate effect on primary prevention strategies and vaccine development.

emm typing of M nontypeable invasive group A streptococcal isolates in Israel

We performed emm typing of M nontypeable invasive group A streptococcal (GAS) isolates collected in a prospective population-based study in Israel. One hundred twenty of 131 isolates (92%) had emm sequences compatible with GAS, consisting of 51 different emm types. Eleven isolates were found to be group G streptococcus. Of the 120 isolates, 55 (46%) belonged to 32 types for which there were no typing sera available in the Streptococcal Reference Laboratory in Israel. The other 65 (64%) isolates, consisting of 19 types, had sera available and therefore could have been serotyped. Forty-three isolates had T and emm types which were not correlated according to standard M-typing protocols and were therefore missed. The principal effect of emm typing was the addition of 32 types not previously identified in Israel and the discovery of new associations between emm and T types. emm typing did not significantly change the proportion of M types; the five most common types were 3, 28, 2, 62, and 41. Twenty different types comprised 80% of all isolates. No new emm sequences were discovered. emm typing emphasized the unusually low incidence of M1 strains causing severe disease in Israel. As serological typing of GAS becomes more problematic due to lack of sera and the appearance of new emm types, reference laboratories should replace M typing with emm sequence typing. Development of a GAS vaccine relies on the emm type distributions in different geographical locations. In our study, 7% of isolates (types 41 and 62) are not included in a 26-valent vaccine that is being studied.

Epidemiologic analysis of invasive and noninvasive group a streptococcal isolates in Hong Kong

Since the mid-1980s, there has been a resurgence of severe forms of invasive group A streptococcal (GAS) disease in many Western countries. In Hong Kong, a similar increase has also been observed in recent years. One hundred seven GAS isolates collected from 1995 to 1998 from individuals with necrotizing fasciitis, toxic shock syndrome, meningitis, or other type of bacteremic sepsis (invasive group, n = 24) as well as from individuals with minor skin and throat infections (noninvasive group, n = 83) were characterized through serologic and/or emm sequence typing. Thirty-two M protein gene sequence types were identified. Types M1, M4, and M12 were the most prevalent in both the invasive group and the noninvasive group; together they accounted for 70.8 and 37.3% of the isolates, respectively. No clear pattern of skin and throat infection M types was observed. Type M1 was overrepresented in the invasive and pharyngeal isolates. The same pulsed-field gel electrophoresis pattern was shared by most invasive and all pharyngeal M1 isolates. Overall, resistance to erythromycin (32%) and tetracycline (53%) was high, but M1 isolates were significantly less likely to have resistance to either antimicrobial agent than non-M1 isolates. One novel emm sequence type, stHK, was identified in an isolate from a patient with necrotizing fasciitis. Minor emm gene sequence alterations were noted for 31 isolates, and for 13 of these isolates, deletion, insertion, or point mutations were seen in the hypervariable 50 N-terminal residues.

emm Typing of group A streptococcus clinical isolates: identification of dominant types for throat and skin isolates

T and emm types were determined for group A streptococci isolated from patients with various infections during 1990-1999 in Toyama Prefecture, Japan. Out of 906 isolates, 872 isolates were divided into 20 T serotypes, and 34 isoltes were T nontypeable (TNT). T12, T1, and T4 were dominant among 699 throat isolates; on the other hand, T11, T28, TB3264, and TNT were dominant among 80 skin isolates. The emm types of 190 isolates were determined following specific PCR amplification and sequencing of the products. Twenty T serotypes were divided into 34 T type/emm type combinations. Thirty-four TNT isolates were divided into 14 emm types, in which emm58 was the most common (38%). Among 82 throat isolates randomly selected, predominant T types T12, T1, and T4 isolates were of the respective same numbers in emm type. T11/emm89, T28/emm28, TB3264/emm13w, and TNT/emm58 were predominant among 80 skin isolates. emm-type distribution observed in the present study was that usually reported in the western world. To our knowledge, 3 T/emm is a novel combination. These results show that emm typing allows the characterization of group A streptococci from various sources.

Epidemiology of invasive group a streptococcus disease in the United States, 1995-1999

Severe invasive group A streptococcal (GAS) disease is believed to have reemerged during the past 10-20 years. We conducted active, laboratory, population-based surveillance in 5 US states (total population, 13,214,992). From 1 July 1995 through 31 December 1999, we identified 2002 episodes of invasive GAS (3.5 cases per 100,000 persons). Rates varied by age (higher among those <2 or >/=65 years old), surveillance area, and race (higher among black individuals) but did not increase during the study period. The 5 most common emm types (1, 28, 12, 3, and 11) accounted for 49.2% of isolates; newly characterized emm types accounted for 8.9% of isolates. Older age; presence of streptococcal toxic shock syndrome, meningitis, or pneumonia; and infection with emm1 or emm3 were all independent predictors of death. We estimate that 9600-9700 cases of invasive GAS disease occur in the United States each year, resulting in 1100-1300 deaths.

Invasive group a streptococcal infections, Israel

We conducted a prospective, nationwide, population-based study of invasive group A streptococcal infections in Israel. We identified 409 patients (median age 27 years; range <1-92), for an annual incidence of 3.7/100,000 (11/100,000 in Jerusalem). The mortality rate was 5%. Bacteremia occurred in 125 cases (31%). The most common illnesses were soft-tissue infection (63%) and primary bacteremia (14%). Thirty percent of patients had no identifiable risk factors for infection. Eighty-seven percent of pharyngeal carriers had the same serotype as the index patient. M types included M3 (25%), M28 (10%), and M-nontypable (33%). A marked paucity of M1 serotype (1.2%) was detected. The results highlighted concentrated pockets of invasive disease in the Jewish orthodox community (annual incidence 16/100,000).

Extension of the Lancefield classification for group A streptococci by addition of 22 new M protein gene sequence types from clinical isolates: emm103 to emm124

Classic M protein serotyping has been invaluable during the past 60 years for the determination of relationships between different group A streptococci (GAS) strains and the varied clinical manifestations inflicted by these organisms worldwide. Nonetheless, during the past 20 years, the difficulties of continued expansion of the serology-based Lancefield classification scheme for GAS have become increasingly apparent. By use of a less demanding sequence-based methodology that closely adheres to previously established strain criteria while being predictive of known M protein serotypes, we recently added types emm94-emm102 to the Lancefield scheme. Continued expansion by the addition of types emm103 to emm124 are now proposed. As with types emm94-emm102, each of these new emm types was represented by multiple independent isolates recovered from serious disease manifestations, each was M protein nontypeable with all typing sera stocks available to international GAS reference laboratories, and each demonstrated antiphagocytic properties in vitro by multiplying in normal human blood.