M protein gene type distribution among group A streptococcal clinical isolates recovered in Mexico City, Mexico, from 1991 to 2000, and Durango, Mexico, from 1998 to 1999: overlap with type distribution within the United States

Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review

The high strain diversity of Streptococcus pyogenes serves as a major obstacle to vaccine development against this leading global pathogen. We did a systematic review of studies in PubMed, MEDLINE, and Embase that reported the global distribution of S pyogenes emm-types and emm-clusters from Jan 1, 1990, to Feb 23, 2023. 212 datasets were included from 55 countries, encompassing 74 468 bacterial isolates belonging to 211 emm-types. Globally, an inverse correlation was observed between strain diversity and the UNDP Human Development Index (HDI; r=-0·72; p<0·0001), which remained consistent upon subanalysis by global region and site of infection. Greater strain diversity was associated with a lower HDI, suggesting the role of social determinants in diseases caused by S pyogenes. We used a population-weighted analysis to adjust for the disproportionate number of epidemiological studies from high-income countries and identified 15 key representative isolates as vaccine targets. Strong strain type associations were observed between the site of infection (invasive, skin, and throat) and several streptococcal lineages. In conclusion, the development of a truly global vaccine to reduce the immense burden of diseases caused by S pyogenes should consider the multidimensional diversity of the pathogen, including its social and environmental context, and not merely its geographical distribution.

Decoding the molecular epidemiology of group A streptococcus - an Indian perspective

PURPOSE

Unlike western countries the knowledge of group A streptococcus (GAS) epidemiology in India remains patchy and incomplete. Typing is crucial for surveillance as well as in predicting the efficacy of multivalent M protein vaccine. The present study aimed to explore the emm types of 206 invasive and non-invasive GAS isolates from South India as well as reviewing all the published literature on GAS molecular epidemiology from India thereby generating a pan-Indian data to predict the conjectural coverage of the 30-valent M-protein vaccine in this population.

METHODOLOGY

emm typing and superantigen (SAg) profiling of GAS along with reviewing literatures on GAS molecular epidemiology from India.

RESULTS

This study revealed a high diversity of emm types with emm 63, 82, 183, 85, 92, 169, 42, 44, 106, 74, 12 being frequently encountered, belonging to twenty emm clusters. The pan-Indian data on prevalent emm types further supports our study findings with 135 emm different types. Six clusters dominated accounting for 80 % of the GAS isolates: E3(26 %), E6(20 %), E2(11 %), E4(10 %), D4(7 %), E1(6 %). No significant association was noted between emm types and the nature of infection (P≥0.05) while a few SAg profiles were significantly associated with certain emm types. Pan Indian data revealed that only 16 % of the emm types encountered were included in proposed 30-valent M protein based vaccine.

CONCLUSION

The coverage among the South Indian GAS isolates was 28.2 % which increased to only 46.6 % with the cross-opsonic effect, thus highlighting the importance of developing a specific multivalent vaccine including the prevalent emm types in India or considering the use of conserved C-repeat vaccines and non-M protein based vaccines.

Protective immunity induced by an intranasal multivalent vaccine comprising 10 Lactococcus lactis strains expressing highly prevalent M-protein antigens derived from Group A Streptococcus

Streptococcus pyogenes (group A Streptococcus) causes diseases ranging from mild pharyngitis to severe invasive infections. The N-terminal fragment of streptococcal M protein elicits protective antibodies and is an attractive vaccine target. However, this N- terminal fragment is hypervariable: there are more than 200 different M types. In this study, an intranasal live bacterial vaccine comprising 10 strains of Lactococcus lactis, each expressing one N-terminal fragment of M protein, has been developed. Live bacterial-vectored vaccines cost less to manufacture because the processes involved are less complex than those required for production of protein subunit vaccines. Moreover, intranasal administration does not require syringes or specialized personnel. Evaluation of individual vaccine types (M1, M2, M3, M4, M6, M9, M12, M22, M28 and M77) showed that most of them protected mice against challenge with virulent S. pyogenes. All 10 strains combined in a 10-valent vaccine (M×10) induced serum and bronchoalveolar lavage IgG titers that ranged from three- to 10-fold those of unimmunized mice. After intranasal challenge with M28 streptococci, survival of M×10-immunized mice was significantly higher than that of unimmunized mice. In contrast, when mice were challenged with M75 streptococci, survival of M×10-immunized mice did not differ significantly from that of unimmunized mice. Mx-10 immunized mice had significantly less S. pyogenes in oropharyngeal washes and developed less severe disease symptoms after challenge than did unimmunized mice. Our L. lactis-based vaccine may provide an alternative solution to development of broadly protective group A streptococcal vaccines.

Nursing Home Outbreak of Invasive Group A Streptococcal Infections Caused by 2 Distinct Strains

Objective.

To identify factors contributing to a cluster of deaths from invasive group A streptococcus (GAS) infection in a nursing home facility and to prevent additional cases.

Design.

Outbreak investigation.

Setting.

A 146-bed nursing home facility in northern Nevada.

Methods.

We defined a case as the isolation of GAS from a normally sterile site in a resident of nursing home A. To identify case patients, we reviewed resident records from nursing home A, the local hospital, and the hospital laboratory. We obtained oropharyngeal and skin lesion swabs from staff and residents to assess GAS colonization and performed emm typing on available isolates. To identify potential risk factors for transmission, we performed a cohort study and investigated concurrent illness among residents and surveyed staff regarding infection control practices.

Results.

Six residents met the case patient definition; 3 (50%) of them died. Among invasive GAS isolates available for analysis, 2 distinct strains were identified: emm11 (3 isolates) and emm89 (2 isolates). The rate of GAS carriage was 6% among residents and 4% among staff; carriage isolates were emm89 (8 isolates), emm11 (2 isolates), and emm1 (1 isolate). Concurrently, 35 (24%) of the residents developed a respiratory illness of unknown etiology; 41% of these persons died. Twenty-one (30%) of the surveyed employees did not always wash their hands before patient contacts, and 27 (38%) did not always wash their hands between patient contacts.

Conclusions.

Concurrent respiratory illness likely contributed to an outbreak of invasive GAS infection from 2 strains in a highly susceptible population. This outbreak highlights the importance of appropriate infection control measures, including respiratory hygiene practices, in nursing home facilities.

Molecular epidemiology and genomics of group A Streptococcus

Streptococcus pyogenes (group A Streptococcus; GAS) is a strict human pathogen with a very high prevalence worldwide. This review highlights the genetic organization of the species and the important ecological considerations that impact its evolution. Recent advances are presented on the topics of molecular epidemiology, population biology, molecular basis for genetic change, genome structure and genetic flux, phylogenomics and closely related streptococcal species, and the long- and short-term evolution of GAS. The application of whole genome sequence data to addressing key biological questions is discussed.

Geoepidemiological hints about Streptococcus pyogenes strains in relationship with acute rheumatic fever

Group A Streptococcus (GAS) strains are lately classified on the basis of sequence variations in the emm gene encoding the M protein, but despite the high number of distinct emm genotypes, the spectrum of phenotypes varying from invasive suppurative to non-suppurative GAS-related disorders has still to be defined. The relationship of GAS types with the uprising of acute rheumatic fever (ARF), a multisystemic disease caused by misdirected anti-GAS response in predisposed people, is also obscure. Studies published over the last 15 years were retrieved from PubMed using the keywords: "Streptococcus pyogenes" or "group A Streptococcus" and "acute rheumatic fever": the prevalence of peculiar emm types across different countries of the world is highly variable, depending on research designs, year of observation, country involved, patients' age, and gender. Most studies revealed that a relatively small number of specific emm/M protein types can be considered "rheumatogenic", as potentially characterized by the possibility of inducing ARF, with remarkable differences between developing and developed countries. The association between emm types and post-streptococcal manifestations is challenging, however surveillance of disease-causing variants in a specific community with high rate of ARF should be reinforced with the final goal of developing a potential primary prophylaxis against GAS infections.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Evaluation of emm gene types, toxin gene profiles and clonal relatedness of group A streptococci

The aim of this study is to evaluate antibiotic susceptibilities, emm gene types, toxin gene profiles and clonal relatedness of group A streptococci (GAS) isolates obtained from patients and carriers. A total of 79 clinical isolates from patients and 60 isolates from carriers were included in the study. Emm typing, toxin gene detection for speA, speB, speC, speG and smeZ genes and pulsed-field gel electrophoresis (PFGE) was performed. Twenty-one distinct emm types were detected; the most common types were emm12, emm89, emm1, emm77, emm4 and emm3. The detection rates of both emm types and the toxin genes didn't differ significantly between patients and carriers. The presence of speA and smeZ was significantly higher in emm1 and speG was significantly lower in emm4 when compared to the other emm types. The rate of clustering obtained with PFGE wasn't significantly different in patients and carriers. As a result, twelve of the 21 emm types detected in this study were covered by the 26-valent vaccine, constituting 77.7% of the emm typeable isolates; however the emm4 type which is one of the most common types in the present study is not among this coverage.

Group A Streptococcus emm gene types in pharyngeal isolates, Ontario, Canada, 2002-2010

Determination of emm variations may help improve vaccine design.

Group A Streptococcus (GAS) is a human-adapted pathogen that causes a variety of diseases, including pharyngitis and invasive infections. GAS strains are categorized by variation in the nucleotide sequence of the gene (emm) that encodes the M protein. To identify the emm types of GAS strains causing pharyngitis in Ontario, Canada, we sequenced the hypervariable region of the emm gene in 4,635 pharyngeal GAS isolates collected during 2002–2010. The most prevalent emm types varied little from year to year. In contrast, fine-scale geographic analysis identified inter-site variability in the most common emm types. Additionally, we observed fluctuations in yearly frequency of emm3 strains from pharyngitis patients that coincided with peaks of emm3 invasive infections. We also discovered a striking increase in frequency of emm89 strains among isolates from patients with pharyngitis and invasive disease. These findings about the epidemiology of GAS are potentially useful for vaccine research.

M-protein gene-type distribution and hyaluronic acid capsule in group AStreptococcusclinical isolates in Chile: association ofemmgene markers withcsrRalleles

Streptococcus pyogenescauses a variety of infections because of virulence factors such as capsular hyaluronic acid and M protein. The aim of this study was to determineemmtypes and capsule phenotype in 110 isolates ofS. pyogenesfrom patients with invasive (sterile sites) and non-invasive (mainly pharyngitis) infections in Chile, and the relationship between both virulence factors. The most abundant types found wereemm12,emm1,emm4andemm28and their distribution was similar to that seen in Latin America and developed countries, but very different from that in Asia and Pacific Island countries. Ten of 16emmtypes identified in pharyngeal isolates were found in sterile-site isolates, and three of nineemmtypes of sterile-site isolates occurred in pharyngeal isolates; threeemmsubtypes were novel. The amount of hyaluronic acid was significantly higher in sterile-site isolates but did not differ substantially amongemmtypes. Only three isolates were markedly capsulate and two of them had mutations in thecsrRgene that codes for a repressor of capsule synthesis genes. We found a non-random association betweenemmtypes andcsrRgene alleles suggesting that horizontal gene transfer is not freely occurring in the population.

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.

Tissue tropisms in group A streptococcal infections

Group A Streptococcus (GAS) is a human-specific pathogen that is highly prevalent throughout the world. The vast majority of GAS infections lead to a mild disease involving the epithelial surfaces of either the throat or skin. The concept of distinct sets of 'throat' and 'skin' strains of GAS has long been conceived. From an ecological standpoint, the epithelium of the throat and skin are important because it is where the organism is most successful in reproducing and transmitting to new hosts. This article examines key features of the epidemiology, population biology and molecular pathogenesis that underlie the tissue site preferences for infection exhibited by GAS, with an emphasis on work from our laboratory on skin tropisms. Recombinational replacement with orthologous gene forms, following interspecies transfer, appears to be an important genetic step leading up to the exploitation of new niches by GAS.

Differences among group A streptococcus epidemiological landscapes: consequences for M protein-based vaccines?

Group A streptococcus (GAS) is a bacterial pathogen responsible for a wide array of disease pathologies in humans. GAS surface M protein plays multiple key roles in pathogenesis, and serves as a target for typing and vaccine development. In this review, we have compiled GAS epidemiological studies from several countries around the world to highlight the consequences on the theoretical efficacy of two different M protein-based vaccine strategies.

Population biology of the human restricted pathogen, Streptococcus pyogenes

Streptococcus pyogenes, also referred to as beta-hemolytic group A streptococci, are strictly human pathogens with a global distribution and high prevalence of infection. The organisms are characterized by high levels of genetic recombination, extensive strain diversity, and a narrow habitat. This review highlights many key features of the population genetics and molecular epidemiology of this biologically diverse bacterial species, with special emphasis on ecological subdivisions and tissue-specific infections, strain diversity and population dynamics in communities, selection pressures arising from the specific host immune response and antibiotic exposure, and within-host selection during the course of invasive disease.

Population biology of the human restricted pathogen, Streptococcus pyogenes

Streptococcus pyogenes, also referred to as beta-hemolytic group A streptococci, are strictly human pathogens with a global distribution and high prevalence of infection. The organisms are characterized by high levels of genetic recombination, extensive strain diversity, and a narrow habitat. This review highlights many key features of the population genetics and molecular epidemiology of this biologically diverse bacterial species, with special emphasis on ecological subdivisions and tissue-specific infections, strain diversity and population dynamics in communities, selection pressures arising from the specific host immune response and antibiotic exposure, and within-host selection during the course of invasive disease.

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.

Genetic analysis of group A streptococcus isolates recovered during acute glomerulonephritis outbreaks in Guizhou Province of China

In this study, 68 group A streptococcus (GAS) isolates associated with two outbreaks of acute glomerulonephritis (AGN) in China were analyzed by emm typing. A total of 11 different emm types were identified. Analysis of emm type distribution suggested that AGN outbreaks in two counties were caused by emm60.1- and emm63.0-type GAS. These two types were further characterized by pulsed-field gel electrophoresis, multilocus sequence typing, sof sequence typing, and PCR-based identification of streptococcal pyrogenic exotoxin A, B, and C (speA, speB, and speC) genes. In antimicrobial susceptibility tests, all outbreak strains were resistant to erythromycin and tetracycline, and the rates of resistance of nonoutbreak strains to the two antibiotics were 63.6% and 90.9%. This study is also the first to report a nephritogenic M63 GAS strain.

Distribution of emm types and subtypes among noninvasive group A, C and G streptococcal isolates in western Norway

Characterization of the reservoir of beta-hemolytic streptococci in a community may shed light on the pathogenesis of severe infections caused by these bacteria. We used emm sequence typing to characterize group A streptococci (GAS), group C streptococci (GCS) and group G streptococci (GGS) in community isolates associated with noninvasive disease in western Norway. A total of 165 isolates during a 13-month period were examined. Skin and throat isolates accounted for 123 and 16, respectively, and the remaining 26 isolates were from other non-sterile sites. We identified 18 previously validated emm types and one novel subtype, emm11.7, among the 101 GAS isolates. The two predominant types, emm28 and 12, were found in 40.6% of the GAS isolates. Compared to other recent studies of noninvasive GAS infections from elsewhere in the world, we found a higher frequency of emm82 (5.9%) and emm87 (12.9%) and a lower frequency of emm1 (4.0%) and emm3 (4.0%). We found a different distribution of GAS emm types compared to a previous study from western Norway. Among the 64 isolates of GCS and GGS, 15 previously described emm types and four novel subtypes, stC1400.5, stCK401.3, stG6.3 and stG652.3, were found, stG6, stG643 and stG485 were the most prevalent types and accounted for 59.4% of the GCS and GGS isolates. The high proportion of skin isolates in the present study may indicate the existence of GAS, GCS and GGS strains with predominantly skin and soft tissue tropism in our community.

Comparative analysis of emm type pattern of Group A Streptococcus throat and skin isolates from India and their association with closely related SIC, a streptococcal virulence factor

Background

Group A streptococcus (GAS) causes a wide variety of life threatening diseases in humans and the incidence of such infections is high in developing countries like India. Although distribution of emm types of GAS in India has been described, there is a lack of data describing either the comparative distribution of emm types in throat versus skin isolates, or the distribution of certain virulence factors amongst these isolates. Therefore in the present study we have monitored the emm type pattern of Group A streptococcus throat and skin isolates from India. Additionally, the association of these isolates with closely related sic (crs), a multifunctional compliment binding virulence factor, was also explored.

Results

Of the 94 (46 throat and 48 skin) isolates analyzed, 37 emm types were identified. The most frequently observed emm types were emm49 (8.5%) and emm112 (7.5%) followed by 6.5% each of emm1-2, emm75, emm77, and emm81. Out of 37 emm types, 27 have been previously reported and rest were isolated for the first time in the Indian Community. The predominant emm types of throat (emm49 and emm75) samples were different from those of skin (emm44, emm81 and emm112) samples. After screening all the 94 isolates, the crs gene was found in six emm1-2 (crs1-2) isolates, which was confirmed by DNA sequencing and expression analysis. Despite the polymorphic nature of crs, no intravariation was observed within crs1-2. However, insertions and deletions of highly variable sizes were noticed in comparison to CRS isolated from other emm types (emm1.0, emm57). CRS1-2 showed maximum homology with CRS57, but the genomic location of crs1-2 was found to be the same as that of sic1.0. Further, among crs positive isolates, speA was only present in skin samples thus suggesting possible role of speA in tissue tropism.

Conclusion

Despite the diversity in emm type pattern of throat and skin isolates, no significant association between emm type and source of isolation was observed. The finding that the crs gene is highly conserved even in two different variants of emm1-2 GAS (speA +ve and -ve) suggests a single allele of crs may be prevalent in the highly diverse throat and skin isolates of GAS in India.

Relationships between emm and multilocus sequence types within a global collection of Streptococcus pyogenes

Background

The M type-specific surface protein antigens encoded by the 5' end of emm genes are targets of protective host immunity and attractive vaccine candidates against infection by Streptococcus pyogenes, a global human pathogen. A history of genetic change in emm was evaluated for a worldwide collection of > 500 S. pyogenes isolates that were defined for genetic background by multilocus sequence typing of housekeeping genes.

Results

Organisms were categorized by genotypes that roughly correspond to throat specialists, skin specialists, and generalists often recovered from infections at either tissue site. Recovery of distant clones sharing the same emm type was ~4-fold higher for skin specialists and generalists, as compared to throat specialists. Importantly, emm type was often a poor marker for clone. Recovery of clones that underwent recombinational replacement with a new emm type was most evident for the throat and skin specialists. The average ratio of nonsynonymous substitutions per nonsynonymous site (Ka) and synonymous substitutions per synonymous site (Ks) was 4.9, 1.5 and 1.3 for emm types of the throat specialist, skin specialist and generalist groups, respectively.

Conclusion

Data indicate that the relationships between emm type and genetic background differ among the three host tissue-related groups, and that the selection pressures acting on emm appear to be strongest for the throat specialists. Since positive selection is likely due in part to a protective host immune response, the findings may have important implications for vaccine design and vaccination strategies.

Invasive group A streptococcal infection in older adults in long-term care facilities and the community, United States, 1998-2003

Invasive infection develops almost 6 times as frequently in the elderly in long-term care facilities.

Limited information exists on the incidence and characteristics of invasive group A streptococcal (GAS) infections among residents of long-term care facilities (LTCFs). We reviewed cases of invasive GAS infections occurring among persons >65 years of age identified through active, population-based surveillance from 1998 through 2003. We identified 1,762 invasive GAS cases among persons >65 years, including 1,662 with known residence type (LTCF or community). Incidence of invasive GAS infection among LTCF residents compared to community-based elderly was 41.0 versus 6.9 cases per 100,000 population. LTCF case-patients were 1.5 times as likely to die from the infection as community-based case-patients (33% vs. 21%, p<0.01) but were less often hospitalized (90% vs. 95%, p<0.01). In multivariate logistic regression modeling, LTCF residence remained an independent predictor of death. Additional prevention strategies against GAS infection in this high-risk population are urgently needed.

Molecular and Clinical Characteristics of Invasive Group A Streptococcal Infection in Sweden

BACKGROUND

The incidence and severity of invasive group A streptococcal infection demonstrate great variability over time, which at least, in part, seems to be related to group A streptococcal type distribution among the human population.

METHODS

An enhanced surveillance study of invasive group A streptococcal infection (746 isolates) was performed in Sweden from April 2002 through December 2004. Noninvasive isolates from either the throat or skin (773 isolates) were collected in parallel for comparison. Clinical and epidemiological data were obtained from 88% of patients with invasive disease and were related to isolate characteristics, including T type, emm sequence type, and the presence of 9 superantigen genes, as well as pulsed-field gel electrophoresis pattern comparisons of selected isolates.

RESULTS

The annual incidence was 3.0 cases per 100,000 population. Among the patients with invasive disease, 11% developed streptococcal toxic shock syndrome, and 9.5% developed necrotizing fasciitis. The overall case-fatality rate was 14.5%, and 39% of the patients with streptococcal toxic shock syndrome died (P<.001). The T3/13/B3264 cluster accounted for 33% of invasive and 25% of noninvasive isolates. Among this most prevalent type cluster, emm types 89 and 81 dominated. Combined results from pulsed-field gel electrophoresis, emm typing, and superantigen gene profiling identified subgroups within specific emm types that are significantly more prone to cause invasive disease than were other isolates of the same type.

CONCLUSIONS

This study revealed a changing epidemiology of invasive group A streptococcal infection in Sweden, with emergence of new emm types that were previously not described. The results also suggest that some clones may be particularly prone to cause invasive disease.

Molecular epidemiology of group A streptococcus causing scarlet fever in northern Taiwan, 2001-2002

In this study, 830 Streptococcus pyogenes isolates collected between 2001 and 2002 from patients with scarlet fever in northern Taiwan were analyzed by M protein gene (emm) sequence typing, pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing. A total of 21 emm types and 56 PFGE patterns were identified. The most frequent emm types were emm1 (29.2%), emm4 (24.1%), emm12 (19.0%), emm6 (15.8%), stIL103 (5.7%), and emm22 (1.9%). Antimicrobial resistance profiles were determined, and resistance to erythromycin (24.6%), clindamycin (2.0%), and chloramphenicol (1.3%) was detected. Five major emm types (emm4, emm12, emm1, emm22, and emm6) accounted for 95.6% of the erythromycin-resistant isolates. The decreased prevalence of erythromycin-resistant emm12 strains coincided with the overall decrease in erythromycin resistance from 32.1% in 2001 to 21.1% in 2002 in Taiwan. Five major clones (emm4/2000, emm12/0000, emm4/2010, emm1/1000, and emm22/8100) represented 72.1% of the erythromycin-resistant isolates. The survey of group A Streptococcus emm types, genetic diversity, and antibiotic resistance has direct relevance to current antimicrobial use policies and potential vaccine development strategies.

Population genetics and linkage analysis of loci within the FCT region of Streptococcus pyogenes

The FCT regions of Streptococcus pyogenes strains encode a variety of cell wall-anchored surface proteins that bind the extracellular matrix of the human host and/or give rise to pilus-like appendages. Strong linkage is evident between transcription-regulatory loci positioned within the FCT and emm regions and the emm pattern genotype marker for preferred infection of the throat or skin. These findings provide a basis for the hypothesis that FCT region gene products contribute to tissue-specific infection. In an initial series of steps to address this possibility, the FCT regions of 13 strains underwent comparative sequence analysis, the gene content of the FCT region was characterized for 113 strains via PCR, and genetic linkage was assessed. A history of extensive recombination within FCT regions was evident. The emm pattern D-defined skin specialist strains were highly homogenous in their FCT region gene contents, whereas the emm pattern A-C-defined throat specialist strains displayed a greater variety of forms. Most pattern A-C strains harbored prtF1 (75%) but lacked cpa (75%). In contrast, the majority of emm pattern D strains had cpa (92%) but lacked prtF1 (79%). Models based on FCT and emm region genotypes revealed the most parsimonious pathways of evolution. Using niche-determining candidate genes to infer phylogeny, emm pattern E strains--the so-called generalists, which lack a strong tissue site preference--occupied a transition zone separating most throat specialists from skin specialists. Overall, population genetic analysis supports the possibility that the FCT region gives rise to surface proteins that are largely necessary, but not always sufficient, to confer tissue site preference for infection.

Differences between Belgian and Brazilian group A Streptococcus epidemiologic landscape

Background

Group A Streptococcus (GAS) clinical and molecular epidemiology varies with location and time. These differences are not or are poorly understood.

Methods and Findings

We prospectively studied the epidemiology of GAS infections among children in outpatient hospital clinics in Brussels (Belgium) and Brasília (Brazil). Clinical questionnaires were filled out and microbiological sampling was performed. GAS isolates were emm-typed according to the Center for Disease Control protocol. emm pattern was predicted for each isolate. 334 GAS isolates were recovered from 706 children. Skin infections were frequent in Brasília (48% of the GAS infections), whereas pharyngitis were predominant (88%) in Brussels. The mean age of children with GAS pharyngitis in Brussels was lower than in Brasília (65/92 months, p<0.001). emm-typing revealed striking differences between Brazilian and Belgian GAS isolates. While 20 distinct emm-types were identified among 200 Belgian isolates, 48 were found among 128 Brazilian isolates. Belgian isolates belong mainly to emm pattern A–C (55%) and E (42.5%) while emm pattern E (51.5%) and D (36%) were predominant in Brasília. In Brasília, emm pattern D isolates were recovered from 18.5% of the pharyngitis, although this emm pattern is supposed to have a skin tropism. By contrast, A–C pattern isolates were unfrequently recovered in a region where rheumatic fever is still highly prevalent.

Conclusions

Epidemiologic features of GAS from a pediatric population were very different in an industrialised country and a low incomes region, not only in term of clinical presentation, but also in terms of genetic diversity and distribution of emm patterns. These differences should be taken into account for designing treatment guidelines and vaccine strategies.

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.

Characterization of group A streptococci (Streptococcus pyogenes): correlation of M-protein and emm-gene type with T-protein agglutination pattern and serum opacity factor

Strain characterization of group A streptococci (GAS) has traditionally been based on serological identification of M protein. Additional tests to determine T-protein serotype and production of streptococcal serum opacity factor (SOF) provide important information both to aid in and to supplement M-protein serotyping. Advances in DNA-sequencing technology in the late twentieth century resulted in the development of a method for determining the M type of GAS from the sequence of the gene encoding M protein, the emm gene. Although emm-sequence typing has largely replaced M typing in many laboratories, information provided by T typing and SOF determination continues to provide valuable supplementary information for strain characterization. A comprehensive summary of the correlation of T pattern and SOF production with M type was last published in 1993, several years before emm typing became widely available. Since then, the ease of M-type identification afforded by emm typing has resulted in an increase in the number of confirmed M/emm types of more than 50 %. However, comprehensive information about T-protein serotype and the correlation of SOF production with these new M/emm types is not widely available. This report presents a comprehensive summary of this information, not only for newly described types, but also updated information for previously described types. This information was extracted from combined records from streptococcal reference laboratories at the University of Minnesota and at the Centers for Disease Control and Prevention in Atlanta. Data from more than 40,000 strains (representing uncomplicated GAS infections, systemic invasive infections and strains associated with non-suppurative sequelae, collected from the US and diverse locations worldwide) were analysed.

Age influences the emm type distribution of pediatric group A streptococcal pharyngeal isolates

BACKGROUND

emm types 12, 1, 28, 3, 4, 2 and 6 (in that order) are the types most commonly associated with uncomplicated group A streptococcal (GAS) pharyngitis in the United States, together accounting for approximately 78% of isolates.

OBJECTIVE

To determine whether the distribution of common pharyngeal group A streptococcal GAS types differs at various ages throughout childhood.

STUDY DESIGN

We emm typed 3356 GAS isolates collected from the United States and Canada during 3 streptococcal seasons (2000-2003). Variations in prevalence by age for the 7 most prevalent emm types and the "uncommon" category (all types accounting for <5% of the total number of isolates) were analyzed and assessed for significance by chi2.

RESULTS

The proportion of uncommon isolates increased significantly with increasing age from 18% in group 1 to 37% in group 4 (P = 0.001). We found a significant decrease in the proportion of the common pharyngeal emm types, specifically emm 12 and emm 4 type isolates, with increasing age (P = 0.001 and P = 0.003, respectively); there was no significant decline in the prevalence of other common pharyngeal types (emm 1, 2, 3, 6 and 28) with increasing age.

CONCLUSION

Age-related changes in emm type distribution of pharyngeal GAS are present in childhood; these changes may reflect acquisition of immunity to more common types as a consequence of exposure early in life, but this remains to be demonstrated.

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.

Growth characteristics of and virulence factor production by group A Streptococcus during cultivation in human saliva

Group A Streptococcus (GAS) commonly infects the human oropharynx, but the initial molecular events governing this process are poorly understood. Saliva is a major component of the innate and acquired immune defense in this anatomic site. Although landmark studies were done more than 60 years ago, investigation of GAS-saliva interaction has not been addressed extensively in recent years. Serotype M1 GAS strain MGAS5005 cultured in human saliva grew to approximately 10(7) CFU/ml and, remarkably, maintained this density for up to 28 days. Strains of several other M-protein serotypes had similar initial growth patterns but did not maintain as high a CFU count during prolonged culture. As revealed by analysis of the growth of isogenic mutant strains, the ability of GAS to maintain high numbers of CFU/ml during the prolonged stationary phase in saliva was dependent on production of streptococcal inhibitor of complement (Sic) and streptococcal pyrogenic exotoxin B (SpeB). During cultivation in human saliva, GAS had growth-phase-dependent production of multiple proven and putative extracellular virulence factors, including Sic, SpeB, streptococcal pyrogenic exotoxin A, Mac protein, and streptococcal phospholipase A(2). Our results clearly show that GAS responds in a complex fashion to growth in human saliva, suggesting that the molecular processes that enhance colonization and survival in the upper respiratory tract of humans are well under way before the organism reaches the epithelial cell surface.

Identity and prevalence of multilocus sequence typing-defined clones of group A streptococci within a hospital setting

Between July and October 2003, 121 clinical isolates of group A streptococci (GAS) were collected from a London hospital and characterized by multilocus sequence typing (MLST) to determine the identity and prevalence of clones circulating within this setting. A total of 39 sequence types (ST), of which 20 were represented by a single isolate, were identified. The eight most prevalent clones among the 121 GAS were ST117/emm81 (16%), ST39/emm4 (9%), ST62/emm87 (7%), ST28/emm1 (6%), ST36/emm12 (6%), ST46/emm22 (5%), ST334/emm82 (5%), and ST101/emm89 (4%). Compared to those in the MLST database (http://spyogenes.mlst.net), 12 (31%) of the 39 STs had not been previously identified, although 7 of these differed from recognized STs at only a single locus, suggesting they were closely related to previously recognized strains. Resistance to erythromycin and tetracycline was seen in 7 and 20% of isolates, respectively, with four isolates resistant to both agents. GAS strains with higher (>80) emm types accounted for 45% of GAS isolates collected during this study. Continuing GAS surveillance, using easily comparable methods, is important for detecting changes in the character of disease-causing isolates.

Molecular heterogeneity among north Indian isolates of Group A Streptococcus

AIM

To monitor molecular heterogeneity among the clinical isolates of group A Streptococcus (GAS) from north India by Vir and emm typing.

METHODS AND RESULTS

GAS isolates, 31 from pharyngitis and nine from rheumatic fever (RF)/rheumatic heart disease (RHD) patients were differentiated into 16 Vir types (VT). These isolates were further discriminated into 23 emm types. Most of emm types were Vir type specific, except few (7.5%), which revealed different Vir types within same emm type. The most prevalent emm type found was emm 49 (15%) followed by 7.5% of emm 69, emm 71 and emm 75 which were different from emm type distribution reported from south India.

CONCLUSIONS

Analysis of data revealed 40% heterogeneity by Vir typing and 57.5% by emm typing among GAS isolates which is significant in view of small number of isolates studied. SIGNIFICANCE OF IMPACT OF THE STUDY: The molecular study for the first time demonstrates different emm types prevalent and circulating in northern region of India and such data may help in selection of types for 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.