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.     

Streptococcus pyogenes Isolates Causing Severe Infections in Norway in 2006 to 2007: emm Types,Multilocus Sequence Types,and Superantigen Profiles

To investigate the epidemiological patterns and genetic characteristics of disease caused by group A Streptococcus (GAS), all available isolates from invasive cases in Norway during 2006 to 2007 (262 isolates) were subjected to antimicrobial susceptibility testing, T serotyping, emm typing, and multilocus sequence typing and screened for known streptococcal pyrogenic exotoxin (Spe) genes, smeZ, and ssa. The average incidence rate was 3.1 cases per 100,000 individuals. The most prevalent sequence types (STs) were STs 52, 28, and 334. In association with emm types 28, 77, and 87, the serotype T-28 comprised 24.8% of the strains. emm types 28, 1, and 82 were dominating. In 2007, a sharp increase in the number of emm-6 strains was noted. All strains were sensitive to penicillin and quinupristin-dalfopristin, while 3.4% and 6.1% of the strains were resistant to macrolides and tetracycline, respectively. Furthermore, the emm-6 strains had intermediate susceptibility to ofloxacin. Isolates displayed a wide variety of gene profiles, as shown by the presence or absence of the Spe genes, smeZ, and ssa, but 48% of the isolates fell into one of three profiles. In most cases, an emm type was restricted to one gene profile. Although the incidence decreased during this study, invasive GAS disease still has a high endemic rate, with involvement of both established and emerging emm types displaying variability in virulence gene profiles as well as differences in gender and age group preferences.Group A streptococcus (GAS), Streptococcus pyogenes, is a highly prevalent Gram-positive human pathogen with a worldwide distribution. Most often, it causes superficial infections of the upper respiratory tract and of the skin, leading to pharyngitis and impetigo, respectively. Invasive GAS infections, on the other hand, can be life-threatening due to conditions such as bacteremia, cellulitis, erysipelas, meningitis, and pneumonia, including the severe manifestations of necrotizing fasciitis (NF) and streptococcal toxic shock syndrome (STSS) (8). In a historical perspective, GAS has been associated with high fatality rates due to severe scarlet fever, puerperal sepsis, and systemic disease (24). With the introduction of antibiotics in the 1940s, incidence rates of severe GAS infections dropped in developed countries and stayed low until the 1980s. Increased virulence and invasiveness then resulted in an increased number of reported septicemia, NF, and STSS cases in previously healthy children and adults in the United States and Europe (14, 33, 49).S. pyogenes harbors a large number of virulence factors that contribute to its complex pathogenicity (7, 12). One of the major virulence factors, the M protein, encoded by the emm gene, confers antiphagocytic properties and induces a type-specific host immune response. Another important group of virulence factors, targeted by anti-T sera, are the pilin proteins, producing pilus-like structures (40) involved in adhesion and invasion of eukaryotic cells and in biofilm formation (1, 31). The streptococcal pyrogenic exotoxins (Spe proteins), a family of bacterial superantigens, are potent immunostimulators associated with disease conditions such as acute rheumatic fever, scarlet fever, and STSS (12, 54). In total, 11 superantigens have been identified in GAS to date, including SpeA, SpeC, SpeG to -M, streptococcal mitogenic exotoxin Z (SmeZ), and streptococcal superantigen (SSA). Because of an issue with the naming of some of the more recently discovered superantigens and for the sake of simplicity, SpeK/L (4, 21, 45), SpeL/M (45, 52), and SpeM (52) are here referred to as SpeK, SpeL, and SpeM, respectively. The proteins SpeB, a cysteine protease, and SpeF, a DNase, were previously considered to be superantigens due to contamination with the potent SmeZ protein (7, 44). Except for speG, speJ, and smeZ, most genes encoding superantigens are associated with bacteriophages (4, 17, 18). Phages are believed to be the major contributors to genetic variation in GAS, both between strains and within strains of the same type (2, 4). Isolates of the same emm type usually share a superantigen profile. Variants differing by the presence or absence of one or a few genes may occur, however, and geographic and temporal differences in the superantigen content of strains of a given emm type have been reported (11).The M protein has traditionally been targeted for serotyping of GAS strains because of its importance as a virulence determinant. However, sequencing of the emm gene (3) is now becoming the standard method, and to date, more than 150 emm types have been described (36). Another method, which has been used for the last 50 years and is still an important alternative to serological M typing, is T typing using slide agglutination tests (39). Multilocus sequence typing (MLST), a widely used method for genetic characterization of organisms of a bacterial species, which is based on the nucleotide sequence variation in seven housekeeping genes, provides unambiguous results that are easily comparable between laboratories (15). Although geographical and temporal variation has been described for GAS populations (15, 35, 47), strains with the same emm type isolated as much as 50 years apart may harbor identical allelic profiles (15) and share the same T type (23). Due to the clonal population structure of S. pyogenes strains, results obtained by T typing, emm typing, and MLST correlate with each other (15, 23, 53).Norway experienced relatively low incidence rates of severe GAS disease after the introduction of antibiotics, but in the mid-1980s there was an increased occurrence of severe invasive disease, especially in otherwise healthy young adults, largely caused by M-1 strains (9, 33). Thereafter, until the early 2000s, there was a significant decrease in the frequency of emm-1 strains and, at the same time, an increase in diversity among the Norwegian GAS strains (37). Antibiotic resistance levels were generally very low in Norway during this period (37).In more recent reports from the United States (2000 to 2004) and the United Kingdom (2003 to 2004), emm-1 and emm-3 strains were still among the most frequent strains found in invasive GAS disease (29, 43). The overall distributions of the most prevalent emm types in Europe and the United States during this period were in congruence, but there were marked differences in the emm type distributions between countries such as Norway''s neighbors, Denmark, Finland, and Sweden (29). The most prominent difference was seen in Finland, where 45% of the strains were emm-28 strains (29). Recently, Finland also reported a rapid change in genotype prevalence caused by the previously uncommon emm type 84 during 2005 to 2007 (50).The distribution of GAS strains and the virulence factors associated with the different strains are not stable over time. Therefore, epidemiological studies targeting genetic types, important virulence factors, and the antimicrobial susceptibility status of these microorganisms are of basic importance for detection of new emerging clones, determination of their potential to cause disease, and development and refinement of vaccines. To provide better insight into the current epidemiological situation for severe GAS infections in Norway, we characterized all available isolates from invasive GAS disease obtained in 2006 to 2007, using emm typing, MLST, spe gene profiling, including smeZ and ssa, and antibiotic resistance screening using selected antibiotics.     

Changing Epidemiology of Streptococcus pyogenes emm Types and Associated Invasive and Noninvasive Infections in Southern Taiwan

A total of 242 isolates were recovered from 76 patients with invasive diseases, 89 with scarlet fever, and 77 with pharyngitis. The most frequent emm types were types 12 (43.4%), 4 (18.2%), and 1 (16.9%). emm12 reemerged in 2005 and peaked in 2007. emm11 was recovered only from patients with invasive disease.Streptococcus pyogenes, a group A Streptococcus (GAS) species, produces many diseases, ranging from impetigo, pharyngitis, and scarlet fever to life-threatening sepsis, necrotizing fasciitis, and streptococcal toxic shock syndrome (STSS) (8). M protein that is encoded by the emm gene is a major virulence factor of GAS. Different M protein types are epidemiologically related to particular clinical syndromes; e.g., emm28 was isolated more frequently than other types among women with puerperal sepsis (6, 10, 14). M1, M2, M3, M4, M6, M18, and M22 strains are associated with outbreaks of scarlet fever (1, 11, 15, 18, 20, 22-24), while M1 and M3 are highly associated with severe invasive disease (19, 25, 27) and M18 is associated with acute rheumatic fever (7).The distribution of emm types in cases of invasive diseases tends to vary over time and within different geographic regions. In the United States, the most common emm types were 1, 28, 12, 3, and 11 during the period from 1995 to 1999 (19). emm types 1, 3, and 12 were predominant from 2000 to 2004 (21). In Europe, the distribution of the emm types differs among countries (16). For example, in Denmark, emm1 and emm28 were the most prevalent types from 2001 to 2004, whereas in Greece, emm1 and emm12 were predominant from 2003 to 2005. In Sweden, four emm types, 89, 81, 28, and 1, accounted for 56% of 746 patients with invasive GAS diseases during the period from 2002 to 2004. In Taiwan, emm1 associated with invasive GAS disease, while emm12 was more often associated with noninvasive GAS disease (13). The purpose of the current study was to investigate the changing epidemiology, genetic diversity, and epidemic virulence of GAS infections over a 10-year period in southern Taiwan, utilizing M genotyping and pulsed-field gel electrophoresis (PFGE) analysis.Clinical isolates of S. pyogenes was obtained from patients seen at the National Cheng Kung University Hospital, Tainan City, Taiwan, from 1998 to 2007. They were divided into strains isolated from patients with invasive diseases or those from patients with noninvasive diseases. Invasive isolates were defined as those obtained from sterile body sites (blood, cerebrospinal, joint, pleural, peritoneal, or pericardial fluids) or from nonsterile sites (wounds associated with STSS or necrotizing fasciitis). Noninvasive strains were defined as GAS isolates obtained from patients with asymptomatic nasopharyngeal colonization, pharyngitis, scarlet fever, erysipelas, and impetigo.A total of 242 nonduplicate GAS isolates recovered from normally sterile sites (165 from throat swabs, 30 from wounds, 25 from pus, 12 from blood, 10 from other materials) were collected. The mean age of patients with invasive diseases was significantly greater than that of those with noninvasive diseases (28.5 ± 27 years versus 8.7 ± 7.9 years [P < 0.0001]). Among the 76 patients with invasive diseases, 58 (76.3%) patients had skin and soft-tissue infections. Three had necrotizing fasciitis, eight had STSS, four had severe sepsis, and three had complicated infections including pneumonia or mastoiditis. Among the 166 patients with noninvasive diseases, 77 (46%) had pharyngitis (including one with lymphadenitis), and 89 (54%) had scarlet fever (including 59 patients with pharyngitis).The distribution of emm types among patients with invasive and noninvasive diseases (subdivided into those with scarlet fever and those with pharyngitis) is shown in Table ​Table1.1. GAS emm sequence typing was based on the 5′ end of the emm gene within the emm chromosomal region (2, 3). A unique emm type was defined as having ≥95% sequence identity to any other known emm type over 160 bp near the 5′ end of the gene, using a BLAST search (http://www.cdc.gov/ncidod/biotech/strep/strepblast.htm). Twenty emm sequence types were identified among the 242 GAS isolates, including types 1, 4, 6, 11, 12, 13, 22, 33, 49, 57, 77, 81, 82, 85, 87, 92, 94, 101, 102, and 123. The leading emm types were 12 (43.4%), 4 (18.2%), 1 (16.9%), 11 (4.5%), 6 (3.7%), and 22 (2.5%) (Table ​(Table1).1). All of the emm types were associated with both invasive and noninvasive diseases except for emm11, which was recovered only from patients with invasive disease. emm22 and other less frequent types were more likely to be associated with invasive diseases (P < 0.0001). The emm types 1, 4, 6, and 12 accounted for 82.2% of all patients with GAS infections, 95.2% of the patients with noninvasive diseases, and 53.9% of the patients with invasive disease. The most common type, emm12, was also significantly associated with noninvasive disease (85.7%) (P < 0.0001).

TABLE 1.

Distribution of Streptococcus pyogenes emm types isolated from 1998 to 2007 according to clinical characteristics

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.     

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.     

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.     

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.     

Emergence of type I restriction modification system‐negative emm1 type Streptococcus pyogenes clinical isolates in Japan

Streptococcus pyogenes emm1 type is the dominant cause of streptococcal toxic shock syndrome (STSS) in Japan and many other developed countries. Recently, the number of STSS patients in Japan was reported to be increasing. Hence, we analyzed the S. pyogenes clinical isolates detected in Japan after 2005. We found that the regions encoding the Spy1908–1910 two‐component regulatory system and the adjacent type I restriction modification system were deleted in some emm1 type isolates. The isolates with the deletion were detected only in the emm1 strains that were isolated between 2010 and 2013, but not before 2010. Twenty‐six of 46 (56.5%) emm1 type isolates were isolated in 2010–2013, and among these isolates, five of seven (71.4%) emm1 type STSS isolates were shown to have that deletion. PFGE and PCR analysis for the presence of several pyrogenic exotoxin‐related genes suggested that the emm1 isolates with and without the deletion shared the same genetic background. The emm1 isolates with the deletion could incorporate exogenous plasmids by experimental electroporation transformation far more efficiently. These results suggested that the novel emm1 isolates have occupied a fairly large part of total emm1 isolates.     

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.     

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.     

Molecular characteristics of pharyngeal and invasive emm3 Streptococcus pyogenes strains from Norway, 1988–2003

A major virulence factor of group A streptococci (GAS) is the M protein. Strains with the M3 type are more often associated with necrotizing fasciitis (NF) and streptococcal toxic shock syndrome, and have a higher case fatality rate than strains of other M types. To better understand the epidemiology of M3 GAS strains in Norway, we analyzed 59 invasive and 69 pharyngeal isolates with respect to prophage content, allelic variation in emm3, mtsR encoding the metal transporter of Streptococcus repressor (mtsR), and sclB coding for streptococcal collagen-like protein B. The Norwegian emm3 strains were very homogeneous, mainly harboring the emm allele 3.1 and prophage profile ΦG3.01. Other prophage profiles were transient. The mutation in mtsR known to truncate the protein and result in decreased capacity to cause NF was not found in our isolates. The sclB gene usually harbored five or eight contiguous repeats of a CAAAA pentanucleotide sequence and a highly modular and variable collagen structural motif (CSM) region with 9 and 12 amino acid M3-specific conserved motif repeats distributed across the entire CSM region. Strains with 5 CAAAA repeats emerged in 1993 and these strains were associated with the increase in invasive M3 cases in the period 1993–2003.     

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).     

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.     

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.     

emm and C-Repeat Region Molecular Typing of Beta-Hemolytic Streptococci in a Tropical Country: Implications for Vaccine Development

We designed a study to investigate the molecular epidemiology of group A streptococcal (GAS) and group C and G streptococcal (GCS and GGS) disease in Fiji, a country which is known to have a high burden of streptococcal disease. Molecular typing of the N-terminal portion (emm typing) of the M protein was performed with 817 isolates (535 GAS and 282 GCS/GGS). We also performed genotyping of the C-repeat region in 769 of these isolates to identify J14 sequence types. The profile of emm types for Fiji was very different from that found for the United States and Europe. There were no dominant emm types and a large number of overlapping types among clinical disease states. Commonly found GAS emm types in industrialized countries, including emm1, emm12, and emm28, were not found among GAS isolates from Fiji. Over 93% of GAS isolates and over 99% of GCS/GGS isolates that underwent J14 sequence typing contained either J14.0 or J14.1. Our data have implications for GAS vaccine development in developing countries and suggest that a vaccine based upon the conserved region of the M protein may be a feasible option for Fiji and potentially for other tropical developing countries.The group A streptococcus (GAS) is an important cause of morbidity and mortality globally, with variation in disease burden between populations (9). A greater burden of GAS disease occurs in developing countries, particularly those located in the tropics, than in industrialized nations (9). The spectrums of GAS disease also differ between developed and developing countries. In many developing countries, GAS impetigo is often endemic, with resultant high rates of acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease leading to at least 200,000 deaths annually, and the burden of invasive disease has probably been underestimated (9, 43). In industrialized countries, a massive number of cases of GAS pharyngitis leads to significant economic impact (27) and invasive disease leads to a significant number of deaths (25, 26).The molecular epidemiologies of GAS disease appear to differ between industrialized and developing nations, although there is a paucity of data from developing nations (5, 9). There are a number of different methods used to characterize GAS, with sequence typing of the 5′ N-terminal end of the M protein gene (emm) the most widely used (3, 17, 18). There have been recent large epidemiologic studies that have used emm sequence typing to investigate the molecular epidemiology of GAS pharyngitis and invasive GAS disease in industrialized nations, most notably in the United States, Canada, and Europe (16, 26, 37) (R. R. Tanz, S. T. Shulman, W. Kabat, E. Kabat, E. Cederlund, D. Patel, Z. Li, V. Sakota, J. B. Dale, and B. Beall, presented at the XVIth Lancefield International Symposium on Streptococci and Streptococcal Diseases, Palm Cove, Queensland, Australia, 2005). Far fewer studies have been conducted in developing nations. The limited available data suggest that numerous new emm types and subtypes have been discovered that have not previously been observed in industrialized countries (40, 45), that the diversity of emm types in developing countries is greater than that in industrialized countries (23, 32-34, 40, 45), and that the majority of isolates are of emm types traditionally associated with impetigo, irrespective of the clinical site of recovery of the isolates (5, 6, 23, 33, 40).Molecular epidemiologic data have implications for vaccine design. Although a number of antigens have shown promise as potential vaccine candidates, only one vaccine, a 26-valent M-protein-based vaccine, has reached clinical trials in recent times (15, 24). Serotypes for this vaccine were chosen if they were known to be common causes of invasive GAS disease or uncomplicated pharyngitis in the United States or if they were associated with rheumatic fever in classical studies from the United States in the mid-20th century (14). While this vaccine is likely to be efficacious in the United States, concerns have been raised about the transferability of this vaccine to developing-country settings (8).Alternative approaches to a multivalent vaccine strategy include the development of a conserved-epitope vaccine. A number of conserved epitopes have been identified and are under investigation, including some within the portion of the M protein closest to the cell wall (the C-repeat region) which appear to be relatively conserved (2, 11, 31, 36). An example is the J8 peptide, a B-cell epitope, contained within the larger sequence J14 (named J14.0 in this article for clarity) (28, 29). Following the discovery of J14.0, a number of J14 sequence types have been identified (47). To date, across all C-repeat regions, there have been 55 different J14 sequence types described, which have been named in the order that they have been discovered (J14.0 to J14.54) (47). Typing of the C-repeat region by the J14 sequence type of GAS has been employed previously (47). J14 sequence type is relevant to J8 because antibodies raised against J8 in mice provide cross-protective immunity against GAS isolates containing J14.0 and J14.1 (Michael Batzloff, Queensland Institute of Medical Research, unpublished data). Antibodies raised against the J14.0 peptide in mice have been shown to opsonize GAS strains belonging to a variety of emm subtypes that contain J14 sequences other than the J14.0 sequence type, including J14.2 (47).Group C streptococci (GCS) and group G streptococci (GGS) are emerging infectious agents, particularly as a cause of invasive disease and of epidemic pharyngitis (19, 35, 48). We have observed higher than expected rates of invasive GCS/GGS in Fiji, as well as high pharyngeal carriage among school children (43). There is also some evidence to suggest that these organisms may play a role in the pathogenesis of acute rheumatic fever and poststreptococcal glomerulonephritis (13, 30). There are very few data regarding emm sequence typing of GCS/GGS and no available data regarding sequence typing of the C-repeat region of these organisms (22).We designed a study to investigate the molecular epidemiology of GAS and GCS/GGS disease in a tropical setting known to have a high burden of invasive, pharyngeal, and impetiginous streptococcal disease (42-44). Because of the implications for vaccine development, we included molecular typing of both the 5′ end of the M protein (emm sequence typing) and the C-repeat region of the M protein (J14 sequence typing).     

Streptococcus pyogenes emm Types and Clusters during a 7-Year Period (2007 to 2013) in Pharyngeal and Nonpharyngeal Pediatric Isolates

Group A streptococcus (GAS) is an important cause of morbidity and mortality worldwide. Surveillance of emm types has important implications, as it can provide baseline information for possible implementation of vaccination. A total of 1,349 GAS pediatric isolates were collected during a 7-year period (2007 to 2013); emm typing was completed for 1,282 pharyngeal (84%) or nonpharyngeal (16%) isolates, and emm clusters and temporal changes were analyzed. Thirty-five different emm types, including 14 subtypes, were identified. The most prevalent emm types identified were 1 (16.7%), 12 (13.6%), 77 (10.9%), 4 (10.8%), 28 (10.4%), 6 (6.8%), 3 (6.6%), and 89 (6.6%), accounting for 82.3% of total isolates. Rheumatogenic emm types comprised 16.3% of total isolates. The emm types 12, 4, and 77 were more prevalent among pharyngeal isolates, and the emm types 1, 89, 6, 75, and 11 were more prevalent among nonpharyngeal isolates. The emm types identified belonged to 13 emm clusters, and the 8 most prevalent clusters comprised 97% of all isolates. There were statistically significant decreases in the prevalence of emm types 12, 4, 5, and 61 and increases in the prevalence of emm types 89, 75, and 11, compared with the period 2001 to 2006. The proposed 30-valent GAS vaccine, which is currently in preclinical studies, encompasses 97.2% of the emm types detected in our study and 97.4% of the erythromycin-resistant strains. In addition, it includes 93.3% of the emm types involved in bacteremia. A much greater diversity of GAS emm types was identified in our area than described previously. Seasonal fluctuations and the introduction of new emm types were observed. Continuous surveillance of emm types is needed in order to evaluate the possible benefits of an M protein-based GAS vaccine.     

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.     

Genome Sequence of an M3 Strain of Streptococcus pyogenes Reveals a Large-Scale Genomic Rearrangement in Invasive Strains and New Insights into Phage Evolution

Group Astreptococcus (GAS) is a gram-positive bacterial pathogen that causes various suppurative infections and nonsuppurative sequelae. Since the late 1980s, streptococcal toxic-shock like syndrome (STSS) and severe invasive GAS infections have been reported globally. Here we sequenced the genome of serotype M3 strain SSI-1, isolated from an STSS patient in Japan, and compared it with those of other GAS strains. The SSI-1 genome is composed of 1,884,275 bp, and 1.7 Mb of the sequence is highly conserved relative to strain SF370 (serotype M1) and MGAS8232 (serotype M18), and almost completely conserved relative to strain MGAS315 (serotype M3). However, a large genomic rearrangement has been shown to occur across the replication axis between the homologous rrn-comX1 regions and between two prophage-coding regions across the replication axis. Atotal of 1 Mb of chromosomal DNA is inverted across the replication axis. Interestingly, the recombinations between the prophage regions are within the phage genes, and the genes encoding superantigens and mitogenic factors are interchanged between two prophages. This genomic rearrangement occurs in 65% of clinical isolates (64/94) collected after 1990, whereas it is found in only 25% of clinical isolates (7/28) collected before 1985. These observations indicate that streptococcal phages represent important plasticity regions in the GAS chromosome where recombination between homologous phage genes can occur and result not only in new phage derivatives, but also in large chromosomal rearrangements.