Streptococcus pyogenes isolates causing severe infections in Norway in 2006 to 2007: emm types, multilocus sequence types, and superantigen profiles

Recent Scientific Advancements towards a Vaccine against Group A Streptococcus

Group A Streptococcus (GAS), or Streptococcus pyogenes, is a gram-positive bacterium that extensively colonises within the human host. GAS is responsible for causing a range of human infections, such as pharyngitis, impetigo, scarlet fever, septicemia, and necrotising fasciitis. GAS pathogens have the potential to elicit fatal autoimmune sequelae diseases (including rheumatic fever and rheumatic heart diseases) due to recurrent GAS infections, leading to high morbidity and mortality of young children and the elderly worldwide. Antibiotic drugs are the primary method of controlling and treating the early stages of GAS infection; however, the recent identification of clinical GAS isolates with reduced sensitivity to penicillin-adjunctive antibiotics and increasing macrolide resistance is an increasing threat. Vaccination is credited as the most successful medical intervention against infectious diseases since it was discovered by Edward Jenner in 1796. Immunisation with an inactive/live-attenuated whole pathogen or selective pathogen-derived antigens induces a potent adaptive immunity and protection against infectious diseases. Although no GAS vaccines have been approved for the market following more than 100 years of GAS vaccine development, the understanding of GAS pathogenesis and transmission has significantly increased, providing detailed insight into the primary pathogenic proteins, and enhancing GAS vaccine design. This review highlights recent advances in GAS vaccine development, providing detailed data from preclinical and clinical studies across the globe for potential GAS vaccine candidates. Furthermore, the challenges and future perspectives on the development of GAS vaccines are also described.

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.

Distribution of emm, superantigen and other virulence genotypes and detection of phylogenetic relationships in group A streptococcal isolates

Group A streptococci are important pathogens with various virulence factors, such as M protein, superantigens, hemolysins, deoxyribonuclease, and proteases. The aims of this study are to investigate the detection of emm genotypes and other virulence genes, such as SAgs, DNase, protease, antibiotic resistance, and phylogenetic relationships in GAS strains isolated from clinical samples.Test strains were obtained from Çukurova University Balcalı Hospital and regional hospitals in Adana province. The M proteins were detected by sequence analysis of emm genes. SAgs and other virulence gene profiles were determined using the Multiplex-PCR method. The antibiotic susceptibility of the isolates was performed by the disc diffusion method and evaluated according to CLSI criteria. The PFGE method was used to determine the clonal relationship between the strains.The emm gene was positive in 86 isolates. The most common emm genotypes were emm28 (22%), emm1 (18.6%), emm12 (13.9%), and emm3 (11.6%). Also, the most common virulence genes were speG (58.1%), speC (56.9%), sdaB (53.4%), and mac (53.4%). The rates of resistance to erythromycin, clindamycin, levofloxacin, ciprofloxacin and telithromycin were 19.8%, 16.3%, 4.7%, 3.5%, and 3.5%, respectively.As a result, additional regional studies on the detection and prevalence of GAS virulence factors in Turkey are required. We believe that this study will provide valuable information for epidemiological studies on emm sequences, Sags, and other virulence factors of Streptococcus pyogenes in Turkey.

A global snapshot on the prevalent macrolide-resistant emm types of Group A Streptococcus worldwide, their phenotypes and their resistance marker genotypes during the last two decades: A systematic review

Watchful epidemiological surveillance of macrolide-resistant Group A Streptococcus (MRGAS) clones is important owing to the evolutionary and epidemiological dynamic of GAS. Meanwhile, data on the global distribution of MRGAS emm types according to macrolide resistance phenotypes and genotypes are scant and need to be updated. For this, the present systematic review analyses a global set of extensively characterized MRGAS isolates from patients of diverse ages and clinical presentations over approximately two decades (2000 to 2020) and recaps the peculiar epidemiological features of the dominant MRGAS clones. Based on the inclusion and exclusion criteria, 53 articles (3593 macrolide-resistant and 15,951 susceptible isolates) distributed over 23 countries were dissected with a predominance of high-income countries over low-income ones. Although macrolide resistance in GAS is highly variable in different countries, its within-GAS distribution seems not to be random. emm pattern E, 13 major emm types (emm12, 4, 28, 77, 75, 11, 22, 92, 58, 60, 94, 63, 114) and 4 emm clusters (A-C4, E1, E6, and E2) were significantly associated with macrolide resistance. emm patterns A-C and D, 14 major emm types (emm89, 3, 6, 2, 44, 82, 87, 118, 5, 49, 81, 59, 227, 78) and 3 well-defined emm clusters (A-C5, E3, and D4) were significantly associated with macrolide susceptibility. Scrutinizing the tendency of each MRGAS emm type to be significantly associated with specific macrolide resistance phenotype or genotype, interesting vignettes are also unveiled. The 30-valent vaccine covers ~95% of MRGAS isolates. The presented data urge the importance of comprehensive nationwide sustained surveillance of MRGAS circulating clones particularly in Low and Middle income countries where sampling bias is high and GAS epidemiology is obfuscated and needs to be demystified.

Assessment of the Relationship between Clinical Manifestation and Pathogenic Potential of Streptococcus pyogenes Strains-Distribution of Genes and Genotypes of Toxins

Streptococcus pyogenes is one of the most important species among beta-haemolytic streptococci, causing human infections of different localization. It is isolated from clinical specimens relatively frequently. In this study, the frequency and co-occurrence of toxin genes (speA, speB, speC, speH, speJ, speK) among 147 S. pyogenes strains were evaluated, using real-time PCR. In addition, the relationship between the occurrence of these genes and the origin of S. pyogenes strains from selected clinical material was assessed. The speB gene was present with the highest incidence (98.6%), while the speK gene was the least frequent (8.2%) among the tested strains. Based on the presence of the detected genes, the distribution of 17 genotypes was determined. The most common (21.8%), was speA (−) speB (+) speC (−) speH (−) speJ (−) speK (−) genotype. Furthermore, significant variation in the presence of some genes and genotypes of toxins in S. pyogenes strains isolated from different types of clinical material was found. There is a considerable variety and disproportion between the frequency of individual genes and genotypes of toxins in S. pyogenes strains. The relationship between the origin of S. pyogenes isolates and the presence of toxins genes indicates their pathogenic potential in the development of infections of selected localization.

Molecular Characteristics of Streptococcus pyogenes Isolated From Chinese Children With Different Diseases

Streptococcus pyogenes is a bacterial pathogen that causes a wide spectrum of clinical diseases exclusively in humans. The distribution of emm type, antibiotic resistance and virulence gene expression for S. pyogenes varies temporally and geographically, resulting in distinct disease spectra. In this study, we analyzed antibiotic resistance and resistance gene expression patterns among S. pyogenes isolates from pediatric patients in China and investigated the relationship between virulence gene expression, emm type, and disease categories. Forty-two representative emm1.0 and emm12.0 strains (n = 20 and n = 22, respectively) isolated from patients with scarlet fever or obstructive sleep apnea-hypopnea syndrome were subjected to whole-genome sequencing and phylogenetic analysis. These strains were further analyzed for susceptibility to vancomycin. We found a high rate and degree of resistance to macrolides and tetracycline in these strains, which mainly expressed ermB and tetM. The disease category correlated with emm type but not superantigens. The distribution of vanuG and virulence genes were associated with emm type. Previously reported important prophages, such as φHKU16.vir, φHKU488.vir, Φ5005.1, Φ5005.2, and Φ5005.3 encoding streptococcal toxin, and integrative conjugative elements (ICEs) such as ICE-emm12 and ICE-HKU397 encoding macrolide and tetracycline resistance were found present amongst emm1 or emm12 clones from Shenzhen, China.

Patterns of antibiotic nonsusceptibility among invasive group A Streptococcus infections-United States, 2006-2017

BACKGROUND

Treatment of severe group A streptococcal infections requires timely and appropriate antibiotic therapy. We describe the epidemiology of antimicrobial-resistant invasive group A streptococcal (iGAS) infections in the U.S.

METHODS

We analyzed population-based iGAS surveillance data at 10 U.S. sites from 2006-2017. Cases were defined as infection with GAS isolated from normally sterile sites or wounds in patients with necrotizing fasciitis or streptococcal toxic shock syndrome. GAS isolates were emm typed. Antimicrobial susceptibility was determined using broth microdilution or whole genome sequencing. We compared characteristics among patients infected with erythromycin nonsusceptible (EryNS) and clindamycin nonsusceptible (CliNS) strains to those with susceptible infections. We analyzed proportions of EryNS and CliNS among isolates by site, year, risk factors and emm type.

RESULTS

Overall, 17,179 iGAS cases were reported; 14.5% were EryNS. Among isolates tested for both inducible and constitutive CliNS (2011-2017), 14.6% were CliNS. Most (99.8%) CliNS isolates were EryNS. Resistance was highest in 2017 (EryNS: 22.8%; CliNS: 22.0%). All isolates were susceptible to beta-lactams. EryNS and CliNS infections were most frequent among persons aged 18-34 years and in persons residing in long-term care facilities, experiencing homelessness, incarcerated, or who injected drugs. Patterns varied by site. Patients with nonsusceptible infections were significantly less likely to die. Emm types with >30% EryNS or CliNS included: 77, 58, 11, 83, 92.

CONCLUSION

Increasing prevalence of EryNS and CliNS iGAS infections in the U.S. is predominantly due to expansion of several emm types. Clinicians should consider local resistance patterns when treating iGAS infections.

Incidence and Effects of Acquisition of the Phage-Encoded ssa Superantigen Gene in Invasive Group A Streptococcus

The acquisition of the phage-encoded superantigen ssa by scarlet fever-associated group A Streptococcus (Streptococcus pyogenes, GAS) is found in North Asia. Nonetheless, the impact of acquiring ssa by GAS in invasive infections is unclear. This study initially analyzed the prevalence of ssa+ GAS among isolates from sterile tissues and blood. Among 220 isolates in northern Taiwan, the prevalence of ssa+ isolates increased from 1.5% in 2008–2010 to 40% in 2017–2019. Spontaneous mutations in covR/covS, which result in the functional loss of capacity to phosphorylate CovR, are frequently recovered from GAS invasive infection cases. Consistent with this, Phostag western blot results indicated that among the invasive infection isolates studied, 10% of the ssa+ isolates lacked detectable phosphorylated CovR. Transcription of ssa is upregulated in the covS mutant. Furthermore, in emm1 and emm12 covS mutants, ssa deletion significantly reduced their capacity to grow in human whole blood. Finally, this study showed that the ssa gene could be transferred from emm12-type isolates to the emm1-type wild-type strain and covS mutants through phage infection and lysogenic conversion. As the prevalence of ssa+ isolates increased significantly, the role of streptococcal superantigen in GAS pathogenesis, particularly in invasive covR/covS mutants, should be further analyzed.

Streptococcal Throat Carriage among Primary School Children Living in Uyo, Southern Nigeria

Surveillance of the carrier state for β-hemolytic streptococcal (BHS) throat infections remains essential for disease control. Recent published works from Sub-Saharan Africa have suggested a changing epidemiology in the burden of BHS throat infections. The objective of the present study was therefore to determine the prevalence and pattern of BHS throat carriage in school-aged children in Uyo, Akwa Ibom State. This was a prospective cross-sectional study of 276 primary school children in Uyo. Subjects were recruited by multistage random sampling. Obtained throat swabs were cultured on 5% sheep blood agar. Lancefield grouping on positive cultures was done by using the Oxoid Streptococcal Grouping Latex Agglutination Kit, United Kingdom. Antimicrobial susceptibility testing was done with the disk diffusion method. Associations were tested with Fischer's exact test. The prevalence of BHS carriage was 3.3%. Group C Streptococcus was identified in 89% of isolates and Group G Streptococcus in 11%. Younger age and larger household size were associated with asymptomatic streptococcal throat infections. Antimicrobial susceptibility was highest with cefuroxime and clindamycin (89% of isolates each), while 78% of isolates were susceptible to penicillin. None of the tested isolates was susceptible to co-trimoxazole. The prevalence of streptococcal throat carriage in the study area was low. There were no Group A Streptococcus isolates suggesting an evolving epidemiology of BHS disease in the study area.

A prospective survey of Streptococcus pyogenes infections in French Brittany from 2009 to 2017: Comprehensive dynamic of new emergent emm genotypes

Streptococcus pyogenes or group A Streptococcus (GAS) causes diseases ranging from uncomplicated pharyngitis to life-threatening infections. It has complex epidemiology driven by the diversity, the temporal and geographical fluctuations of the circulating strains. Despite the global burden of GAS diseases, there is currently no available vaccination strategy against GAS infections. This study, based on a longitudinal population survey, aimed to understand the dynamic of GAS emm types and to give leads to better recognition of underlying mechanisms for the emergence of successful clones. From 2009 to 2017, we conducted a systematic culture-based diagnosis of GAS infections in a French Brittany population with a prospective recovery of clinical data. The epidemiological analysis was performed using emm typing combined with the structural and functional cluster-typing system for all the recovered strains. Risk factors for the invasiveness, identified by univariate analysis, were computed in a multiple logistic regression analysis, and the only independent risk factor remaining in the model was the age (OR for the entire range [CI_95%] = 6.35 [3.63, 11.10]; p<0.0001). Among the 61 different emm types identified, the most prevalent were emm28 (16%), emm89 (15%), emm1 (14%), and emm4 (8%), which accounted for more than 50% of circulating strains. During the study period, five genotypes identified as emm44, 66, 75, 83, 87 emerged successively and belonged to clusters D4, E2, E3, and E6 that were different from those gathering “Prevalent” emm types (clusters A-C3 to 5, E1 and E4). We previously reported significant genetic modifications for emm44, 66, 83 and 75 types resulting possibly from a short adaptive evolution. Herein we additionally observed that the emergence of a new genotype could occur in a susceptible population having specific risk factors or probably lacking a naturally-acquired cluster-specific immune cross-protection. Among emergent emm types, emm75 and emm87 tend to become prevalent with a stable annual incidence and the risk of a clonal expansion have to be considered.

Prevalent emm Types among Invasive GAS in Europe and North America since Year 2000

BACKGROUND

Streptococcus pyogenes or group A streptococcus (GAS) is an important human pathogen responsible for a broad range of infections, from uncomplicated to more severe and invasive diseases with high mortality and morbidity. Epidemiological surveillance has been crucial to detect changes in the geographical and temporal variation of the disease pattern; for this purpose the M protein gene (emm) gene typing is the most widely used genotyping method, with more than 200 emm types recognized. Molecular epidemiological data have been also used for the development of GAS M protein-based vaccines.

METHODS

The aim of this paper was to provide an updated scenario of the most prevalent GAS emm types responsible for invasive infections in developed countries as Europe and North America (US and Canada), from 1st January 2000 to 31st May 2017. The search, performed in PubMed by the combined use of the terms ("emm") and ("invasive") retrieved 264 articles, of which 38 articles (31 from Europe and 7 from North America) met the inclusion criteria and were selected for this study. Additional five papers cited in the European articles but not retrieved by the search were included.

RESULTS

emm1 represented the dominant type in both Europe and North America, replaced by other emm types in only few occasions. The seven major emm types identified (emm1, emm28, emm89, emm3, emm12, emm4, and emm6) accounted for approximately 50-70% of the total isolates; less common emm types accounted for the remaining 30-50% of the cases. Most of the common emm types are included in either one or both the 26-valent and 30-valent vaccines, though some well-represented emm types found in Europe are not.

CONCLUSION

This study provided a picture of the prevalent emm types among invasive GAS (iGAS) in Europe and North America since the year 2000 onward. Continuous surveillance on the emm-type distribution among iGAS infections is strongly encouraged also to determine the potential coverage of the developing multivalent vaccines.

A complication of meningitis and infective endocarditis due to Streptococcus pyogenes

We described a rare case of meningitis and infective endocarditis (IE) due to Streptococcus pyogenes. An 80-year-old woman was admitted to our hospital with unconsciousness. Glasgow Coma Scale was E1V3M5. We diagnosed her with acute meningitis due to S. pyogenes and started treatment using ceftriaxone. In spite of the improvement of her unconscious state, she developed a new-onset systolic murmur on day 13, and echocardiography revealed severe mitral valve regurgitation with vegetation. Therefore, we also diagnosed her with IE and continued the antibiotics for 6 weeks after we confirmed the negative blood cultures. The patient was finally transferred to another hospital for rehabilitation 57 days after admission. Considering that the number of S. pyogenes infections has been reported to increase in Japan and worldwide, we need to be more careful about the rare complication of meningitis and IE due to S. pyogenes.

Epidemiology of invasive group A streptococcal infections in Norway 2010-2014: A retrospective cohort study

Streptococcus pyogenes or group A streptococcus (GAS) causes mild to severe infections in humans. GAS genotype emm1 is the leading cause of invasive disease worldwide. In the Nordic countries emm28 has been the dominant type since the 1980s. Recently, a resurgence of genotype emm1 was reported from Sweden. Here we present the epidemiology of invasive GAS (iGAS) infections and their association with emm-types in Norway from 2010-2014. We retrospectively collected surveillance data on antimicrobial susceptibility, multilocus sequence type and emm-type, and linked them with demographic and clinical manifestation data to calculate age and sex distributions, major emm- and sequence types and prevalence ratios (PR) on associations between emm-types and clinical manifestations. We analysed 756 iGAS cases and corresponding isolates, with overall incidence of 3.0 per 100000, median age of 59 years (range, 0-102), and male 56 %. Most frequent clinical manifestation was sepsis (49 %) followed by necrotizing fasciitis (9 %). Fifty-two different emm-types and 67 sequence types were identified, distributed into five evolutionary clusters. The most prevalent genotype was emm1 (ST28) in all years (range, 20-33 %) followed by 15 % emm28 in 2014. All isolates were susceptible to penicillin, 15 % resistant to tetracycline and <4 % resistant to erythromycin. A PR of 4.5 (95 % CI, 2.3-8.9) was calculated for emm2 and necrotizing fasciitis. All emm22 isolates were resistant to tetracycline PR 7.5 (95 % CI, 5.8-9.9). This study documented the dominance of emm1, emergence of emm89 and probable import of tetracycline resistant emm112.2 into Norway (2010-2014). Genotype fluctuations between years suggested a mutual exclusive dominance of evolutionary clades.

Antimicrobial Susceptibility of Invasive Streptococcus pyogenes Isolates in Germany during 2003-2013

A nationwide laboratory-based surveillance study of invasive S. pyogenes infections was conducted in Germany. Invasive isolates (n = 1,281) were obtained between 2003 and 2013. All isolates were susceptible to penicillin, cefotaxime and vancomycin. Tetracycline showed the highest rate of resistant or intermediate resistant isolates with 9.8%, followed by macrolides (4.0%), trimethoprim/sulfamethoxazole (SXT) (1.9%), levofloxacin (1.3%), chloramphenicol (0.9%) and clindamycin (0.7%). The most prominent trends were the appearance of levofloxacin non-susceptible isolates since 2011, and an increase of SXT non-susceptibility since 2012.

Epidemiology and emm types of invasive group A streptococcal infections in Finland, 2008-2013

Invasive Streptococcus pyogenes (group A streptococcus, GAS) infections are a major global cause of morbidity and mortality. We analysed the surveillance data on invasive GAS and the microbiological characteristics of corresponding isolates to assess the incidence and emm type distribution of invasive GAS infections in Finland. Cases defined as patients with isolations of blood and cerebrospinal fluid S. pyogenes are mandatorily notified to the National Infectious Disease Registry and sent to the national reference laboratory for emm typing. Antimicrobial data were collected through the network including all clinical microbiology laboratories. Pulsed-field gel electrophoresis (PFGE) analysis was performed to assess clonality. In total, 1165 cases of invasive GAS were reported in Finland during 2008-2013; the median age was 52 years (range, 0-100) and 54% were male. The overall day 7 case fatality rate was 5.1% (59 cases). The average annual incidence was 3.6 cases per 100,000 population. A total of 1122 invasive GAS isolates (96%) were analysed by emm typing; 72 different emm types were identified, of which emm28 (297 isolates, 26%), emm89 (193 isolates, 12%) and emm1 (132 isolates, 12%) were the most common types. During 2008-2013, an increase of erythromycin resistance (1.9% to 8.7%) and clindamycin (0.9% to 9.2%) was observed. This resistance increase was in parallel with the introduction of a novel clone emm33 into Finland. The overall incidence of invasive GAS infections remained stable over the study period in Finland. We identified clonal spread of macrolide-resistant invasive emm33 GAS type, highlighting the importance of molecular surveillance.

Prevalent emm types and superantigen gene patterns of group A Streptococcus in Thailand

Group A Streptococcus (GAS) are globally distributed bacterial pathogens. We examined the emm genotypes, which are important indicators of virulence, of 349 clinical GAS isolates collected using two surveillance systems, i.e. Invasive Bacterial Infection Surveillance (IBIS) from 2010 to 2011 (234 isolates) and routine surveillance of clinically isolated bacteria from various hospitals during 1996-2011 (115 isolates) in Thailand. The major emm genotypes in IBIS samples were emm44 (12·0%), emm104 (6·8%), emm22 (5·6%), and emm81 (5·6%), whereas only one isolate (0·4%) had the emm1 genotype, which is significantly more common in invasive cases in the Western world. In samples collected during routine surveillance, emm238 (10·4%), emm44 (8·7%), and emm165 (7·0%) were dominant. The major superantigen gene profiles were similar between the groups, and 30·1% of isolates did not possess the phage-encoded superantigens (speA, speC, speH, speI, speK, speL, speM, ssa). Although most isolates exhibited limited gene profiles, emm44 isolates had highly variable gene profiles (15 patterns). We conclude that emm44 is the predominant GAS genotype in Thailand, and isolates varied in superantigen gene profiles.

Streptococcus pyogenes strains in Sao Paulo, Brazil: molecular characterization as a basis for StreptInCor coverage capacity analysis

BACKGROUND

Several human diseases are caused by Streptococcus pyogenes, ranging from common infections to autoimmunity. Characterization of the most prevalent strains worldwide is a useful tool for evaluating the coverage capacity of vaccines under development. In this study, a collection of S. pyogenes strains from Sao Paulo, Brazil, was analyzed to describe the diversity of strains and assess the vaccine coverage capacity of StreptInCor.

METHODS

Molecular epidemiology of S. pyogenes strains was performed by emm-genotyping the 229 isolates from different clinical sites, and PCR was used for superantigen profile analysis. The emm-pattern and tissue tropism for these M types were also predicted and compared based on the emm-cluster classification.

RESULTS

The strains were fit into 12 different emm-clusters, revealing a diverse phylogenetic origin and, consequently, different mechanisms of infection and escape of the host immune system. Forty-eight emm-types were distinguished in 229 samples, and the 10 most frequently observed types accounted for 69 % of all isolates, indicating a diverse profile of circulating strains comparable to other countries under development. A similar proportion of E and A-C emm-patterns were observed, whereas pattern D was less frequent, indicating that the strains of this collection primarily had a tissue tropism for the throat. In silico analysis of the coverage capacity of StreptInCor, an M protein-conserved regionally based vaccine candidate developed by our group, had a range of 94.5 % to 59.7 %, with a mean of 71.0 % identity between the vaccine antigen and the predicted amino acid sequence of the emm-types included here.

CONCLUSIONS

This is the first report of S. pyogenes strain characterization in Sao Paulo, one of the largest cities in the world; thus, the strain panel described here is a representative sample for vaccine coverage capacity analysis. Our results enabled evaluation of StreptInCor candidate vaccine coverage capacity against diverse M-types, indicating that the vaccine candidate likely would induce protection against the diverse strains worldwide.

Macrolide-resistant Streptococcus pyogenes: prevalence and treatment strategies

Although penicillin remains the first-choice treatment for Streptococcus pyogenes infection, macrolides are important alternatives for allergic patients and lincosamides are recommended together with β-lactams in invasive infections. S. pyogenes may exhibit macrolide resistance because of active efflux (mef genes) or target modification (erm genes), the latter conferring cross resistance to lincosamides and streptogramin B. Worldwide, resistance is restricted to a limited number of genetic lineages, despite resistance genes being encoded on mobile genetic elements. For reasons that are not completely clear, resistance and the associated phenotypes are highly variable across countries. Although resistance remains high in several countries, particularly in Asia, an overall decreasing trend of resistance has been noted in recent years, mostly in Europe. This decrease is not always accompanied by declines in macrolide consumption, suggesting significant roles of other factors in determining the dynamics of macrolide-resistant clones. Continued surveillance is needed to obtain further insights into the forces governing macrolide resistance in S. pyogenes.

[Epidemiology of Streptococcus pyogenes invasive diseases in France (2007-2011)]

Group A Streptococcus (GAS) is a human pathogen responsible for a wide range of clinical manifestations. An increase of GAS invasive infections has been described since the mid 1980s. To study the French epidemiology of invasive infections (i) we characterized all GAS invasive strains received at the French National Reference Center for streptococci (CNR-Strep) between 2007 and 2011; (ii) we analyzed the epidemiological data on the corresponding strains. For each strain, emm genotype, superantigen genes and antibiotics susceptibility were determined. Among the 2 603 non redundant invasive GAS strains, 65.1 % (n=1 695) were isolated from blood culture. A streptococcal toxic shock syndrome (STSS) was described in 16.4 % (n=428) of cases, mostly associated with necrotizing fasciitis (NF), pleuropulmonary or osteoarticular infections (p ≤0.001). The case fatality rate was 10.6 %. A total of 102 different emm genotypes were identified. Three emm genotypes predominated, reaching nearly 60 % of the strains: emm 1 (26.7 %), emm 28 (16.4 %), and emm 89 (12.8 %). The proportion of each emm genotype varied according to the year and the age of patients. Among those < 15 years old, the three main genotypes were emm 1 (36.8 %), emm 12 (12.9 %) and emm 4 (9.5 %). The distribution of superantigen genes (SpeA, SpeC and Ssa) was restricted to several emm genotypes. Between 2007 and 2011, the rate of macrolides resistant GAS strains decreased from 7.8 to 5.5 %. emm 1 strains are still the most common especially in most severe clinical manifestations including STSS and NF.

Molecular characterization of Streptococcus pyogenes group A isolates from a tertiary hospital in Lebanon

Streptococcus pyogenes [Group A Streptococcus (GAS)] is one of the most important human pathogens, responsible for numerous diseases with diverse clinical manifestations. As the epidemiology of GAS infections evolves, a rapid and reliable characterization of the isolates remains essential for epidemiological analysis and infection control. This study investigated the epidemiological patterns and genetic characteristics of 150 GAS isolates from a tertiary hospital in Lebanon by emm typing, superantigens (SAgs) detection, PFGE and antibiotic profiling. The results revealed 41 distinct emm types, the most prevalent of which were emm89 (16 %), emm12 (10 %), emm2 (9 %) and emm1 (8 %). Testing for the presence of superantigens showed that speB (87 %), ssa (36 %) and speG (30 %) were predominant. PFGE detected 39 pulsotypes when a similarity cut-off value of 80 % was implemented. Antibiotic-susceptibility testing against seven different classes of antibiotics showed that 9 % of the isolates were resistant to clindamycin, 23 % were resistant to erythromycin and 4 % showed the macrolide-lincosamide-streptogramin B (MLSB) phenotype. The emergence of tetracycline-resistant strains (37 %) was high when compared with previous reports from Lebanon. This study provided comprehensive evidence of the epidemiology of GAS in Lebanon, highlighting the association between emm types and toxin genes, and providing valuable information about the origin and dissemination of this pathogen.

Distribution of superantigens in group A streptococcal isolates from Salvador, Brazil

BACKGROUND

Group A streptococcus (GAS) causes invasive disease, superficial disease, and can asymptomatically colonize humans. Superantigens are one virulence factor found in GAS. Previous studies found associations between the genes that encode superantigens and emm type of GAS. It is unknown if these associations are due to underlying biological factors that limit the distribution of superantigens or, alternatively, if these associations are due to the expansion of local GAS linages where these studies took place. To further address this question we screened GAS isolates collected from Salvador, Brazil for 11 known superantigen genes.

METHODS

Seventy-seven GAS isolates were screened by PCR for superantigen genes. These superantigen genes were speA, speC, speG, speH, speI, speJ, speK, speL, speM, ssa, and smeZ. We used Fisher's two-sided exact test to identify associations between superantigens and GAS emm type. We then compared our results to previous reports of superantigen prevalence and superantigen association with emm type.

RESULTS

In our collection we found several emm type and superantigen genotype combinations that have previously been reported in isolates from Europe and Australia. We also found that speA was significantly associated with emm type 1, and that speC was significantly associated with emm type 12.

CONCLUSIONS

Our study reports superantigen genotypes of GAS from a region of the world that is lacking this information. We found evidence of common GAS superantigen genotypes that are spread worldwide as well as novel superantigen genotypes that, so far, are unique to Brazil.

Invasive infections due to Streptococcus pyogenes: seasonal variation of severity and clinical characteristics, Iceland, 1975 to 2012

Epidemiology and clinical characteristics of invasive Group A streptococcal infections (IGASI) are highly variable. Long-term studies are needed to understand the interplay between epidemiology and virulence. In a population-based study of IGASI in Iceland from 1975 to 2012, 288 cases were identified by positive cultures from normally sterile body sites. Charts were reviewed retrospectively and emm-types of viable Streptococcus pyogenes isolates (n=226) determined. Comparing the first and last decade of the study period, IGASI incidence increased from 1.09 to 3.96 cases per 100,000 inhabitants per year. The most common were emm types 1 (25%), 28 (11%) and 89 (11%); emm1 strains were most likely to cause severe infections. Infections in adults were significantly more likely to be severe during the seasonal peak from January to April (risk ratio: 2.36, 95% confidence interval: 1.34–4.15). Significant seasonal variability in severity was noted among patients with diagnosis of sepsis, respiratory infection and cellulitis, with 38% of severe infections in January to April compared with 16% in other months (p<0.01). A seasonal increase in severity of IGASI suggested that generalised seasonal increase in host susceptibility, rather than introduction of more virulent strains may play a role in the pathogenesis of these potentially fatal infections.

Emergence of Streptococcus pyogenes emm102 causing toxic shock syndrome in Southern Taiwan during 2005-2012

BACKGROUND

Streptococcal toxic shock syndrome (STSS) is an uncommon but life-threatening disease caused by Streptococcus pyogenes.

METHODS

To understand the clinical and molecular characteristics of STSS, we analyzed clinical data and explored the emm types, superantigen genes, and pulsed-field gel electrophoresis of causative S. pyogenes isolates obtained between 2005 and 2012.

RESULTS

In total, 53 patients with STSS were included in this study. The median age of the patients was 57 years (range: 9-83 years), and 81.1% were male. The most prevalent underlying disease was diabetes mellitus (45.3%). Skin and soft-tissue infection accounted for 86.8% of STSS. The overall mortality rate was 32.1%. Underlying diseases had no statistical impact on mortality. A total of 19 different emm types were identified. The most prevalent emm type was emm102 (18.9%), followed by emm11 (17%), emm1 (11.3%), emm87 (9.4%), and emm89 (7.5%). There was no statistically significant association between emm type and a fatal outcome. Among the superantigen genes, speB was the most frequently detected one (92.5%), followed by smeZ (90.6%), speG (81.1%), speC (39.6%), and speF (39.6%). The majority of emm102 strains were found to have speB, speC, speG, and smeZ. The presence of speG was negatively associated with a fatal outcome (P = 0.045).

CONCLUSIONS

Our surveillance revealed the emergence of uncommon emm types, particularly emm102, causing STSS in southern Taiwan. Characterization of clinical, epidemiological, and molecular characteristics of STSS will improve our understanding of this life-threatening disease.

Characteristics of group A Streptococcus strains circulating during scarlet fever epidemic, Beijing, China, 2011

Scarlet fever is one of a variety of diseases caused by group A Streptococcus (GAS). During 2011, a scarlet fever epidemic characterized by peak monthly incidence rates 2.9–6.7 times higher than those in 2006–2010 occurred in Beijing, China. During the epidemic, hospital-based enhanced surveillance for scarlet fever and pharyngitis was conducted to determine characteristics of circulating GAS strains. The surveillance identified 3,359 clinical cases of scarlet fever or pharyngitis. GAS was isolated from 647 of the patients; 76.4% of the strains were type emm12, and 17.1% were emm1. Almost all isolates harbored superantigens speC and ssa. All isolates were susceptible to penicillin, and resistance rates were 96.1% to erythromycin, 93.7% to tetracycline, and 79.4% to clindamycin. Because emm12 type GAS is not the predominant type in other countries, wider surveillance for the possible spread of emm12 type GAS from China to other countries is warranted.

Development of a panel of seven duplex real-time PCR assays for detecting 13 streptococcal superantigens

BACKGROUND

Streptococcal superantigens (SAgs) are the major virulence factors of infection in humans for group A Streptococcus (GAS) bacteria. A panel consisting of seven duplex real-time PCR assays was developed to simultaneously detect 13 streptococcal SAgs and one internal control which may be important in the control of GAS-mediated diseases.

METHODS

Primer and probe sequences were selected based on the highly conserved region from an alignment of nucleotide sequences of the 13 streptococcal SAgs. The reaction conditions of the duplex real-time PCR were optimized and the specificity of the duplex assays was evaluated using SAg positive strains. The limit of detection of the duplex assays was determined by using 10-fold serial dilutions of the DNA of 13 streptococcal SAgs and compared to a conventional polymerase chain reaction (PCR) method for evaluating the duplex assays sensitivity.

RESULTS

Using the duplex assays, we were able to differentiate between 13 SAgs from Streptococcus strains and other non-Streptococcus bacteria without cross-reaction. On the other hand, the limit of detection of the duplex assays was at least one or two log dilutions lower than that of the conventional PCR.

CONCLUSIONS

The panel was highly specific (100%) and the limit of detection of these duplex groups was at least ten times lower than that obtained by using a conventional PCR method.

Severe soft tissue infection caused by a non-beta-hemolytic Streptococcus pyogenes strain harboring a premature stop mutation in the sagC gene

We recovered a non-beta-hemolytic Streptococcus pyogenes strain from a severe soft tissue infection. In this isolate, we detected a premature stop codon within the sagC gene of the streptolysin S (SLS) biosynthetic operon. Reintroduction of full-length sagC gene on a plasmid vector restored the beta-hemolytic phenotype to our clinical isolate, indicating that the point mutation in sagC accounted for loss of hemolytic activity. To the best of our knowledge, this is the first report to demonstrate that a severe soft tissue infection can be caused by a non-beta-hemolytic S. pyogenes strain lacking a functional SagC.

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.

Similar superantigen gene profiles and superantigen activity in norwegian isolates of invasive and non-invasive group a streptococci

Group A streptococcus (GAS) harbours several virulence factors, including M protein (coded by the emm gene) and superantigens (SAgs). SAgs are extracellular toxins that directly activate the immune system by cross-binding to the HLA class II molecule and T cell receptor (TCR), thereby causing activation of up to 30% of the T cells and subsequent massive secretion of cytokines. Forty-eight GAS strains isolated from patients at Norwegian hospitals between 1988 and 2004 were included in this study. Of these, 24 were invasive streptococcal toxic shock syndrome (STSS) or necrotizing fasciitis (NF) isolates and 24 were non-invasive pharyngitis isolates, matched for having the same T-type and year of isolation as the invasive isolates. The isolates were characterized by emm sequence typing, multilocus sequence typing (MLST) and SAg gene profiles. A correlation between T-type, emm type, sequence type and SAg gene profile was revealed. No difference between invasive and non-invasive isolates regarding serotype or genotype was demonstrated. Selected invasive and non-invasive isolates with identical SAg gene profiles were analysed for SAg activity in bacterial growth culture media with and without human cell culture media added. A human T cell proliferation assay was used as measurement for SAg activity and simultaneously we also measured the cytokine content in normal human peripheral blood leucocyte cell culture media. The results revealed that invasive and non-invasive isolates did not differ significantly in SAg activity as it is present in semipurified bacterial culture medium.

Pathogenicity of Bacteria Contaminating Blood Products

SUMMARY: Bacterial contaminations of blood products often originate from the flora of the donor. Normally, components of the skin flora less frequently give rise to severe or complicated infections, although their participation in such conditions has been described. In contrast, bacteria that can cause infections in immunocompetent persons may give rise to life-threatening infections when present in blood products. The latter microorganisms are well-equipped with a variety of virulence factors that contribute to their pathogenicity.

Population biology of Gram-positive pathogens: high-risk clones for dissemination of antibiotic resistance

Infections caused by multiresistant Gram-positive bacteria represent a major health burden in the community as well as in hospitalized patients. Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium are well-known pathogens of hospitalized patients, frequently linked with resistance against multiple antibiotics, compromising effective therapy. Streptococcus pneumoniae and Streptococcus pyogenes are important pathogens in the community and S. aureus has recently emerged as an important community-acquired pathogen. Population genetic studies reveal that recombination prevails as a driving force of genetic diversity in E. faecium, E. faecalis, S. pneumoniae and S. pyogenes, and thus, these species are weakly clonal. Although recombination has a relatively modest role driving the genetic variation of the core genome of S. aureus, the horizontal acquisition of resistance and virulence genes plays a key role in the emergence of new clinically relevant clones in this species. In this review, we discuss the population genetics of E. faecium, E. faecalis, S. pneumoniae, S. pyogenes and S. aureus. Knowledge of the population structure of these pathogens is not only highly relevant for (molecular) epidemiological research but also for identifying the genetic variation that underlies changes in clinical behaviour, to improve our understanding of the pathogenic behaviour of particular clones and to identify novel targets for vaccines or immunotherapy.

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 and molecular analysis of Streptococcus pyogenes isolates causing invasive disease in Spain (1998-2009): comparison with non-invasive isolates

The incidence, clinical manifestations, and circulating clones involved in Streptococcus pyogenes invasive disease was analyzed in two regions of Spain between 1998 and 2009. The annual average incidence of invasive disease was 2 episodes per 100,000 inhabitants (3.1 for children and 1.9 for adults). The most frequent clinical manifestations were cellulitis (41.3%), bacteremia without focus (19.0%), streptococcal toxic shock syndrome (12.6%), and pneumonia (7.7%). Among 247 invasive isolates analyzed, the most prevalent clones were emm1/ST28 (27.9%), emm3/ST15-406 (9.8%), and emm4/ST39 (6.5%). The emm1/ST28 clone was the only clone detected each year throughout the study period and was associated with more than one third of all fatal outcomes. When invasive isolates were compared with 1,189 non-invasive isolates, the emm1/ST28 clone was significantly associated with invasive disease. The speA and ssa genes were more frequent among invasive emm1 and emm4 isolates, respectively. Forty-two (17%) invasive isolates were resistant to erythromycin (21 harbored the mef gene and 21 the ermB or ermA genes). Twenty-two (8.9%) isolates had reduced susceptibility to ciprofloxacin (minimum inhibitory concentration [MIC] 2-8 μg/mL) and 32 (13%) were tetracycline-resistant (tetM or tetO gene). In conclusion, the emm1 type was overrepresented among invasive cases and was associated with high mortality rates.