Epidemiology of Invasive Group A Streptococcal Disease in Alaska, 2001 to 2013

The Arctic Investigations Program (AIP) began surveillance for invasive group A streptococcal (GAS) infections in Alaska in 2000 as part of the invasive bacterial diseases population-based laboratory surveillance program. Between 2001 and 2013, there were 516 cases of GAS infection reported, for an overall annual incidence of 5.8 cases per 100,000 persons with 56 deaths (case fatality rate, 10.7%). Of the 516 confirmed cases of invasive GAS infection, 422 (82%) had isolates available for laboratory analysis. All isolates were susceptible to penicillin, cefotaxime, and levofloxacin. Resistance to tetracycline, erythromycin, and clindamycin was seen in 11% (n = 8), 5.8% (n = 20), and 1.2% (n = 4) of the isolates, respectively. A total of 51 emm types were identified, of which emm1 (11.1%) was the most prevalent, followed by emm82 (8.8%), emm49 (7.8%), emm12 and emm3 (6.6% each), emm89 (6.2%), emm108 (5.5%), emm28 (4.7%), emm92 (4%), and emm41 (3.8%). The five most common emm types accounted for 41% of isolates. The emm types in the proposed 26-valent and 30-valent vaccines accounted for 56% and 78% of all cases, respectively. GAS remains an important cause of invasive bacterial disease in Alaska. Continued surveillance of GAS infections will help improve understanding of the epidemiology of invasive disease, with an impact on disease control, notification of outbreaks, and vaccine development.     

Higher rates of streptococcal colonization among children in the Pacific Rim Region correlates with higher rates of group A streptococcal disease and sequelae

Group A streptococcal (GAS) pharyngeal colonization rates were determined among 1061 asymptomatic students in Hawaii and American Samoa where acute rheumatic fever rates are high. All GAS isolates were emm sequence typed. Although pharyngeal colonization rates were low in Hawaii (3.4%), Pacific Islander children had significantly higher colonization rates (5.7% vs. 1.2% in other ethnic groups, p <0.05). The colonization rate was higher in American Samoa (13%). Few emm types that were infrequently observed in symptomatic infections in Hawaii were repeatedly identified in both sites. These emm types were previously described among asymptomatic children suggesting a type-specific association with pharyngeal colonization.     

Epidemiology Analysis of Streptococcus pyogenes in a Hospital in Southern Taiwan by Use of the Updated emm Cluster Typing System

emm typing is the most widely used molecular typing method for the human pathogen Streptococcus pyogenes (group A streptococcus [GAS]). emm typing is based on a small variable region of the emm gene; however, the emm cluster typing system defines GAS types according to the nearly complete sequence of the emm gene. Therefore, emm cluster typing is considered to provide more information regarding the functional and structural properties of M proteins in different emm types of GAS. In the present study, 677 isolates collected between 1994 and 2008 in a hospital in southern Taiwan were analyzed by the emm cluster typing system. emm clusters A-C4, E1, E6, and A-C3 were the most prevalent emm cluster types and accounted for 67.4% of total isolates. emm clusters A-C4 and E1 were associated with noninvasive diseases, whereas E6 was significantly associated with both invasive and noninvasive manifestations. In addition, emm clusters D4, E2, and E3 were significantly associated with invasive manifestations. Furthermore, we found that the functional properties of M protein, including low fibrinogen-binding and high IgG-binding activities, were correlated significantly with invasive manifestations. In summary, the present study provides updated epidemiological information on GAS emm cluster types in southern Taiwan.     

Distribution of emm genotypes in group A streptococcus isolates of Korean children from 2012 to 2019

ObjectivesChanges in the epidemiology of group A streptococcus (GAS) infection is related to emm genotype. We studied the distribution of emm genotypes and their antibiotic susceptibility among Korean children.MethodsIsolates from children with GAS infection between 2012 and 2019 were collected. emm typing and cluster analysis was performed according to the Centers for Disease Control emm cluster classification. Antimicrobial susceptibility was tested using the E-test and resistance genes were analyzed for macrolide resistant phenotypes.ResultsAmong 169 GAS isolates, 115 were from children with scarlet fever. Among invasive isolates, emm1 (6/22, 27.3%), emm12 (4/22, 18.2%), and emm4 (4/22, 18.2%) were most common. In scarlet fever, although emm4 (38/115, 33.0%) was the most prevalent throughout the study period, emm4 was replaced by emm3 (28/90, 31.1%) during an outbreak in 2017–2018. Among all isolates, only 2 (1.2%) exhibited erythromycin resistance and harbored both ermA and ermB genes.ConclusionsIn this analysis of GAS isolated from Korean children, emm1 was the most prevalent in invasive infection. In scarlet fever, emm4 was prevalent throughout the study period, with an increase in emm3 during 2017–2018. GAS isolates during 2012–2019 demonstrated low erythromycin resistance.     

Epidemiology and Molecular Characterization of Macrolide-Resistant Streptococcus pyogenes in Taiwan

Our multicenter nationwide surveillance data indicated that erythromycin (ERY) resistance among group A Streptococcus (GAS) isolates in Taiwan declined from 53.1% in 1998 and 2000 to 14.6% in 2002 and 2004 and 10.7% in 2006 to 2010 (P < 0.01). The present study aimed to assess the epidemiology of GAS in Taiwan and identify factors associated with ERY resistance. All 127 ERY-resistant (ERY^r) isolates and 128 randomly selected ERY-susceptible (ERY^s) isolates recovered from 1998 to 2010 were emm typed. ERY^r isolates were also characterized by ERY resistance phenotype and mechanisms and pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing was performed on selected ERY^r isolates. The predominant emm types in ERY^r isolates were emm22 (n = 33, 26.0%), emm12 (n = 24, 18.9%), emm4 (n = 21, 16.5%), and emm106 (n = 15, 11.8%). In ERY^s isolates, emm12 (n = 27, 21.9%), emm1 (n = 18, 14.1%), emm106 (n = 16, 12.5%), and emm11 (n = 9, 7.1%) predominated. The most common ERY resistance phenotype was the M phenotype (resistant to macrolides) (70.9%), with all but one isolate carrying mef(A), followed by the constitutive macrolide-lincosamide-streptogramin B resistance (cMLS_B) phenotype (26.8%), with isolates carrying erm(B) or erm(TR). ERY^r isolates of the emm12-sequence type 36 (ST36) lineage with the cMLS_B phenotype were mostly present before 2004, while those of the emm22-ST46 lineage with the M phenotype predominated in later years. Recovery from respiratory (throat swab) specimens was an independent factor associated with ERY resistance. emm1 and emm11 GAS isolates were significantly associated with ERY^s, while emm22 was detected only in ERY^r GAS. In addition, emm106 isolates were prevalent among the abscess/pus isolates, whereas emm12 isolates were strongly associated with a respiratory (throat) origin. In addition to identifying factors associated with ERY resistance in GAS, our study provides helpful information on the changing GAS epidemiology in Taiwan.     

Epidemiological markers of Streptococcus pyogenes strains in Tunisia

To further understand the epidemiology of Streptococcus pyogenes or group A streptococcus (GAS) infections in Tunisia, phenotypic and genomic markers of GAS isolates, including antibiotic susceptibility, biotypes, T and emm types and toxin gene profiles, have been characterized. A total of 103 isolates, collected between 2000 and 2006, were investigated; 47 were recovered from invasive infections, and 56 from non-invasive infections. Rates of tesistance to tetracycline, erythromycin, clindamycin and rifampin were 70.8%, 4.8%, 4.8% and 0.9%, respectively. High levels of resistance to streptomycin and kanamycin were observed in 1.9% and 4.8% of isolates, respectively. Biotype 3 was most common. Twenty different T patterns were observed, with a predominance of T3/13/B3264, and 38 different emm types. In both invasive and non-invasive isolates, emm118 (9.7%), emm42 (8.7%), emm1 (7.8%), st432 (6.8%), emm28 (5.8%) and emm76 (5.8%) were the most prevalent types; emm1, emm76 and emm18 were mainly observed among invasive infections, whereas emm118 (12.5%), emm42 (10.7%) and emm28 (8.9%) were predominant among non-invasive infections. The speB gene was detected in all isolates, but there were variable frequencies of speA, speC and ssa (20.3%, 32% and 25.2% respectively). Significant associations of emm1, emm18 and emm3 with speA and of emm4 and st432 with ssa were found. This first report from Tunisia revealed a unique emm distribution of GAS that differs from those of other regions. This information on the distribution of such emm types will be useful for the development of an appropriate vaccine in a country where the incidence of rheumatic fever remains high.     

Invasive group A,C and G streptococcal disease in western Norway: virulence gene profiles,clinical features and outcomes

Invasive group A streptococcal (iGAS) disease is endemic in Norway, but data on invasive group C and group G streptococcal (iGCS/GGS) disease are lacking. We investigated the characteristics of iGAS and iGCS/GGS infections in western Norway from March 2006 to February 2009. Clinical information was retrospectively obtained from medical records. GAS and GCS/GGS isolates were emm typed and screened for the presence of 11 superantigen (SAg) genes and the gene encoding streptococcal phospholipase A₂ (SlaA). GCS/GGS isolates were also subjected to PCR with primers targeting speG^dys. Sixty iGAS and 50 iGCS/GGS cases were identified, corresponding to mean annual incidence rates of 5.0 per 100 000 and 4.1 per 100 000 inhabitants, respectively. Skin and soft tissue infections were the most frequent clinical manifestations of both iGAS and iGCS/GGS disease, and 14 iGAS patients (23%) developed necrotizing fasciitis. The 30-day case fatality rates of iGAS and iGCS/GGS disease were 10% and 2%, respectively. emm1, emm3 and emm28 accounted for 53% of the GAS isolates, and these types were associated with severe clinical outcome. SAg gene and SlaA profiles were conserved within most of the GAS emm types, although five profiles were obtained within isolates of emm28. stG643 was the most prevalent GCS/GGS emm type, and speG^dys was identified in 73% of the GCS/GGS isolates. Neither GAS SAg genes nor SlaA were detected in GCS/GGS. Our findings indicate a considerable burden of both iGAS and iGCS/GGS disease and a high frequency of necrotizing fasciitis caused by GAS in our community.     

Distribution of <Emphasis Type="Italic">emm</Emphasis> types in invasive and non-invasive group A and G streptococci

Our study describes the emm type distributions of invasive and non-invasive group A streptococci (GAS) and group G streptococci (GGS) strains in one of the biggest Health Districts in Finland. A total of 571 GAS or GGS were recovered from patients with invasive or non-invasive infections during a 1-year period in 2008–2009 in Pirkanmaa Health District in Finland. We describe here the emm type distributions of GAS and GGS collected from throat (n = 246), pus (n = 217), deep tissue (n = 56) and blood (n = 52). The most common emm types among GAS were emm77, emm1, emm28, emm89 and emm12. Among GGS, the most common emm types were stG480, stG643, stG6, stC6979 and stG485. Some emm types were found to associate with certain infection focus. In GAS, emm77 associated with pus isolates, whereas emm1 and emm12 were more frequent among throat isolates. In GGS, stG480 was more commonly found from throat isolates.     

Streptococcus pyogenes bacteraemia, emm types and superantigen profiles

The aim of this study was to investigate the emm types and superantigen profiles of bacteraemic group A streptococcal (GAS; Streptococcus pyogenes) isolates and to detect possible associations between the molecular characteristics of isolates and the clinical presentations of disease. In this population-based study, 87 bacteraemic GAS isolates from adult patients in Pirkanmaa Health District (HD), Finland, during the period 1995–2004 were emm typed and genotyped for superantigen (SAg) profiles. The epidemiological and clinical data of the patients were analysed with the microbiological characterisation data. Among the 87 isolates, 18 different emm types were found. emm1, emm28 and emm81 were the three most common types, covering 52% of isolates. The prevalence of specific emm types showed high variability during the 10-year study period. We could not find any association between the emm type and clinical features of bacteraemic infection, such as underlying diseases, disease manifestations or case fatality. Of nine superantigen genes examined, speA and speC were identified in 20 and 30% of the strains, respectively. No association was found between disease manifestation and the presence of single superantigen genes. The 26-valent GAS vaccine would have covered only 62% of isolates causing invasive disease in Pirkanmaa HD during the study period.     

Distribution of emm types among group A streptococcal isolates from Serbia

This is the first study concerning the molecular epidemiology of group A streptococcus in Serbia and includes 145 isolates from patients with various infections during the period 2001–2007. The emm types, superantigen profile and susceptibility pattern were determined. Among 31 emm types identified, the most prevalent were emm6, emm12, emm1, and emm58. All isolates showed uniform antimicrobial susceptibility to all tested antibiotics, with the exception of tetracycline and erythromycin (41% and 0.7% resistant strains, respectively). Significant heterogeneity of emm types was found, with a high frequency of emm6 and emm58, as well as a considerable prevalence of tetracycline resistance, and a low level of macrolide resistance.     

Clinical and epidemiological aspects of invasive Streptococcus pyogenes infections in Denmark during 2003 and 2004

Active surveillance of invasive group A streptococcal (GAS) infections was conducted in Denmark during 2003 and 2004 as a part of the Strep-EURO initiative. The main objective was to improve understanding of the epidemiology of invasive GAS disease in Denmark. During the 2 years, 278 cases were reported, corresponding to a mean annual incidence of 2.6 cases per 100,000 inhabitants. The vast majority of isolates, 253 (91%), were from blood, with the remaining 25 (9%) being from cerebrospinal fluid, joints, or other normally sterile sites. The mean case fatality rate (CFR) was 20%, with the rate being higher in patients more than 70 years of age (36.5%). For streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis the CFRs were 53% and 25%, respectively. Out of 16 T types recorded, three predominated: T28 (23%), T1 (22%), and the cluster T3/13/B3264 (14%). Among 29 different emm types, emm28 and emm1 accounted for 51% of strains, followed by emm3 (11%), emm89 (7%), and emm12 (5.5%). Low resistance rates were detected for macrolide-lincosamide-streptogramin B (MLS_B) antibiotics (3%) and tetracycline (8%); two isolates exhibited coresistance to tetracycline and macrolides. Of nine pyrogenic exotoxin (superantigen) genes examined, speA and speC were identified in 58% and 40% of the strains, respectively; either of the genes was present in all strains causing STSS. Most strains harbored speG (99%). ssa was present in 14% of the isolates only. In Denmark, as in comparable countries, GAS invasive disease shows a sustained, high endemicity, with involvement of both established and emerging streptococcal emm and T types.     

Molecular characterisation of invasive <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis> isolates from Hungary obtained in 2004 and 2005

Our aim was to characterise by molecular techniques group A streptococci isolated from invasive infections in Hungary in 2004–2005. Twenty-six nonduplicate invasive GAS isolates were selected and examined. The mortality rate proved high (52.3%) for those cases (n = 21) where data were available. Predominant emm types were emm1 (n = 13, 50%) and emm80 (n = 5, 19.2%), but other M types (emm4, emm28, emm66, emm81.1, emm82, emm84) were also identified. Eight different PFGE types were distinguished, and each emm type showed an individual PFGE pattern. Our results show that—similarly to results obtained in several other countries—emm type 1 strains predominate among invasive GAS isolates, and that emm 1 type strains recovered from severe streptococcal infections were associated with the presence of the speA gene. The rate for macrolide resistance proved low: only two isolates showed elevated MICs for erythromycin.     

Superantigen gene complement of Streptococcus pyogenes—relationship with other typing methods and short-term stability

The profiling of the superantigen (SAg) encoding genes has been frequently used as a complementary typing method for group A streptococci (GAS), but a confusing gene nomenclature and a large diversity of primers used in screening has led to some conflicting results. The aim of this work was to develop a polymerase chain reaction (PCR) method capable of efficiently amplifying all the known allelic variants of these genes, and to evaluate the congruence of this methodology with other commonly used molecular typing methods. The presence of the 11 known SAg genes and two other exotoxin-encoding genes (speB and speF) was tested in a collection of 480 clinical GAS isolates, using two multiplex PCR reactions. The SAg gene profile was compared with other typing methods. Four naturally occurring deletions involving the genes speB, speF, and rgg were characterized, two of which were found among invasive isolates. The absence of the chromosomally encoded genes speG and smeZ was supported by Southern blot hybridization and associated with specific GAS lineages, while the presence of phage-encoded genes was more variable. Positive associations between SAg genes or between SAg profiles and emm types or pulsed-field gel electrophoresis (PFGE) clusters were observed. The results suggest that the SAg profile diversifies faster than other properties commonly used for molecular typing, such as emm type and multilocus sequence typing (MLST) sequence types (STs), and can be a useful complement in GAS molecular epidemiology. Still, the short-term stability of the SAg gene profile among prevalent genetic lineages may largely explain the observed associations between SAg genes.     

Decline in macrolide-resistant Streptococcus pyogenes isolates from French children

We studied the macrolide resistance and serotypes of 585 group A streptococcus (GAS) isolates collected from French children with pharyngitis. Nineteen isolates (3.2%) were erythromycin-resistant and harbored the following resistance genes: 31.6% mef(A), 15.8% erm(A), and 52.6% erm(B). The 19 isolates included 7 different emm types (4, 1, 11, 2, 28, 12, and 77) and 7 corresponding multilocus sequence types. The current fall in macrolide consumption has led to a very low rate of GAS macrolide resistance.     

emm gene diversity, superantigen gene profiles and presence of SlaA among clinical isolates of group A, C and G streptococci from western Norway

In order to investigate molecular characteristics of beta-hemolytic streptococcal isolates from western Norway, we analysed the entire emm gene sequences, obtained superantigen gene profiles and determined the prevalence of the gene encoding streptococcal phospholipase A2 (SlaA) of 165 non-invasive and 34 contemporary invasive group A, C and G streptococci (GAS, GCS and GGS). Among the 25 GAS and 26 GCS/GGS emm subtypes identified, only emm3.1 was significantly associated with invasive disease. M protein size variation within GAS and GCS/GGS emm types was frequently identified. Two non-invasive and one invasive GGS possessed emm genes that translated to truncated M proteins as a result of frameshift mutations. Results suggestive of recombinations between emm or emm-like gene segments were found in isolates of emm4 and stG485 types. One non-invasive GGS possessed speC, speG, speH, speI and smeZ, and another non-invasive GGS harboured SlaA. speA and SlaA were over-represented among invasive GAS, probably because they were associated with emm3. speG ^dys was identified in 83% of invasive and 63% of non-invasive GCS/GGS and correlated with certain emm subtypes. Our results indicate the invasive potential of isolates belonging to emm3, and show substantial emm gene diversity and possible lateral gene transfers in our streptococcal population.     

Lateral genetic transfers between group A and G streptococci for M-like genes are ongoing

Previously we described a long-polymerase chain reaction (PCR) method to amplify a 4–7 kb target containing most of the components of the vir regulon (mga,emm-like genes andscpA) in a number of group A streptococcus (GAS) isolates.¹In contrast to GAS, strains of human group G streptococcus (GGS) gave approximately 1.6 or 1.8 kb products. Sequence analysis of the amplified products issued from GGS templates revealed a mosaic consisting of upstream sequence frommga(the gene for positive regulator of vir regulon), an unidentified open reading frame, a short segment ofemm(the gene for M protein, an antiphagocytic molecule) and an upstream sequence ofscp(C5a-peptidase gene). A full lengthscpGis present immediately downstream from the mosaic segment in the human GGS genome. The GGS PCR fragment did not code formgaor full lengthemm. All human GGS isolates are known to code foremmbut the gene is separated fromscpGby at least 10 kb.²Our data, obtained using long-PCR and unrelated strains of GGS, confirm this. We could not detect a homologue ofmgain human GGS by hybridization analysis. The mosaic sequence suggests that enbloc transfer of the vir regulon from GAS to a GGS progenitor may have occurred, following which deletion and rearrangement events may have taken place. Partial nucleotide sequences ofemmcorresponding to the variable domain of M proteins from three local GGS isolates were determined. One sequence (emmGGS6) is 99% identical toemmfrom a geographicaly separated isolate of GGS recently described.³emmGGS6 also has significant homology withemmfrom a GAS strain (STDONALD) isolated from the same geographical area as was GGS6. The twoemmsequences (emmGGS6 andemmSTDONALD) revealed frameshift-compensatory frameshift mutations relative to each other, contributing to lower amino acid homology between the two predicted M proteins. SinceemmSTDONALD has no known relatives within the 80 or soemmsequences in the database, we speculate that it could have been laterally acquired from GGS. Horizontal transfers between GGS and GAS may be ongoing.     

Group A streptococcal infection caused by <Emphasis Type="Italic">emm</Emphasis>1 strains among children in southern Taiwan

The aim of this study was to characterize the molecular epidemiology of invasive and non-invasive group A streptococcus (GAS) infections in children from 1997 through 2004 in southern Taiwan. A collection of 32 invasive and 150 non-invasive isolates were recruited for analysis. emm1 (34.4%) and emm12 (40.0%) predominated in the invasive and non-invasive isolates, respectively. The peak incidence of invasive GAS infection (IGASI) occurred between 2002 and 2003. emm4 and emm12 were the major types among clinical isolates before 2001, and was replaced by emm1 during 2002–2003. All emm1 isolates were clonal relatedness. The declined prevalence of erythromycin resistance occurred in the major shift of the endemic isolates to emm1 strains during 2002–2003 in the community. Financial support: the National Health Research Institute, Taiwan (NHRI-EX90∼EX92-9027SP), and the National Science Council, Taiwan (NSC93-2314-B-006-059).     

A Novel Live Vector Group A Streptococcal emm Type 9 Vaccine Delivered Intranasally Protects Mice against Challenge Infection with emm Type 9 Group A Streptococci

The availability of a protective vaccine against Streptococcus pyogenes (group A Streptococcus [GAS]) is a priority for public health worldwide. Here, we have generated six live vaccine strains, each engineered to express an N-terminal M protein peptide from one of six of the most prevalent emm types of GAS (M1, M2, M4, M9, M12, and M28). The vaccine strains are based on a food-grade Lactococcus lactis strain and do not bear any antibiotic resistance. Mice immunized with the vaccine strain expressing the M9 peptide (termed here the L. lactis M9 strain) showed high titers of serum antibodies when delivered intranasally. Mice immunized with the L. lactis M9 strain were protected against infection after intranasal challenge with type 9 streptococci. Several parameters of disease, such as weight loss, body temperature, colony counts in mouth washes, and lung histology, were significantly improved in immunized mice compared to naive control mice. Our results indicate that intranasal delivery of the L. lactis M9 strain live bacterial vaccine induced GAS-specific IgG titers, prevented pharyngeal colonization of GAS, and protected mice from disease upon challenge. The design of this vaccine prototype may provide a lower cost alternative to vaccines comprised of purified recombinant proteins.     

Updated model of group A Streptococcus M proteins based on a comprehensive worldwide study

Group A Streptococcus (GAS) M protein is an important virulence factor and potential vaccine antigen, and constitutes the basis for strain typing (emm-typing). Although >200 emm-types are characterized, structural data were obtained from only a limited number of emm-types. We aim to evaluate the sequence diversity of near-full-length M proteins from worldwide sources and analyse their structure, sequence conservation and classification. GAS isolates recovered from throughout the world during the last two decades underwent emm-typing and complete emm gene sequencing. Predicted amino acid sequence analyses, secondary structure predictions and vaccine epitope mapping were performed using MUSCLE and Geneious software. A total of 1086 isolates from 31 countries were analysed, representing 175 emm-types. emm-type is predictive of the whole protein structure, independent of geographical origin or clinical association. Findings of an emm-type paired with multiple, highly divergent central regions were not observed. M protein sequence length, the presence or absence of sequence repeats and predicted secondary structure were assessed in the context of the latest vaccine developments. Based on these global data, the M6 protein model is updated to a three representative M protein (M5, M80 and M77) model, to aid in epidemiological analysis, vaccine development and M protein-related pathogenesis studies.