Conservation of C4BP-binding sequence patterns in Streptococcus pyogenes M and Enn proteins.

Antigenically sequence variable M proteins of the major bacterial pathogen Streptococcus pyogenes (Strep A) are responsible for recruiting human C4b-binding protein (C4BP) to the bacterial surface, which enables Strep A to evade destruction by the immune system. The most sequence divergent portion of M proteins, the hypervariable region (HVR), is responsible for binding C4BP. Structural evidence points to the conservation of two C4BP-binding sequence patterns (M2 and M22) in the HVR of numerous M proteins, with this conservation applicable to vaccine immunogen design. These two patterns, however, only partially explain C4BP binding by Strep A. Here, we identified several M proteins that lack these patterns but still bind C4BP and determined the structures of two, M68 and M87 HVRs, in complex with a C4BP fragment. Mutagenesis of these M proteins led to the identification of amino acids that are crucial for C4BP binding, enabling formulation of new C4BP-binding patterns. Mutagenesis was also carried out on M2 and M22 proteins to refine or generate experimentally grounded C4BP-binding patterns. The M22 pattern was the most prevalent among M proteins, followed by the M87 and M2 patterns, while the M68 pattern was rare. These patterns, except for M68, were also evident in numerous M-like Enn proteins. Binding of C4BP via these patterns to Enn proteins was verified. We conclude that C4BP-binding patterns occur frequently in Strep A strains of differing M types, being present in their M or Enn proteins, or frequently both, providing further impetus for their use as vaccine immunogens.

Global epidemiological comparison of Streptococcus pyogenes emm-types associated with pharyngitis and pharyngeal carriage.

OBJECTIVES: To test the prevailing dogma that Streptococcus pyogenes emm-types that cause pharyngitis are the same as those associated with the carriage, using a global dataset. METHODS: Drawing on our systematic review of the global distribution of S. pyogenes emm-types and emm-clusters from 1990 to 2023, we compared the distribution and diversity of strains associated with pharyngitis and pharyngeal carriage, in the context of local United Nations Development Programme Human Development Index (HDI) values. RESULTS: We included 20 222 isolates from 71 studies done in 34 countries, with the vast majority of carriage strain data from studies in 'Low HDI' settings (550/1293; 43%). There was higher emm-type diversity for carriage than pharyngitis strains (Simpson Reciprocal Index of diversity 28.9 vs. 11.4). Compared with pharyngitis strains, carriage emm-types were disproportionately from emm-clusters E and D, usually described as 'generalist' or 'skin' strains. DISCUSSION: A limited number of studies have compared S. pyogenes strains from cases of pharyngitis compared with carriage. Our understanding of strains associated with carriage is the poorest for high-income settings. In low and medium HDI countries, we found greater strain associated with pharyngeal carriage than pharyngitis. Improving our understanding of S. pyogenes carriage epidemiology in the pre-vaccine era will help to decipher the direct and potential indirect effects of vaccines.

Conservation of C4BP-binding Sequence Patterns in Streptococcus pyogenes M and Enn Proteins.

Antigenically sequence variable M proteins of the major bacterial pathogen Streptococcus pyogenes (Strep A) are responsible for recruiting human C4b-binding protein (C4BP) to the bacterial surface, which enables Strep A to evade destruction by the immune system. The most sequence divergent portion of M proteins, the hypervariable region (HVR), is responsible for binding C4BP. Structural evidence points to the conservation of two C4BP-binding sequence patterns (M2 and M22) in the HVR of numerous M proteins, with this conservation applicable to vaccine immunogen design. These two patterns, however, only partially explain C4BP-binding by Strep A. Here, we identified several M proteins that lack these patterns but still bind C4BP, and determined the structures of two, M68 and M87 HVRs, in complex with a C4BP fragment. Mutagenesis of these M proteins led to identification of amino acids that are crucial for C4BP-binding, enabling formulation of new C4BP-binding patterns. Mutagenesis was also carried out on M2 and M22 proteins to refine or generate experimentally grounded C4BP-binding patterns. The M22 pattern was the most populated among M proteins, followed by the M87 and M2 patterns, while the M68 pattern was rare. These patterns, except for M68, were also evident in numerous M-like Enn proteins. Binding of C4BP via these patterns to Enn proteins was verified. We conclude that C4BP-binding patterns occur frequently in Strep A strains of differing M types, being present in their M or Enn proteins, or frequently both, providing further impetus for their use as vaccine immunogens.

Streptococcus pyogenes carriage and infection within households in The Gambia: a longitudinal cohort study.

BACKGROUND: Streptococcus pyogenes causes more than 500 000 deaths per year globally, which occur disproportionately in low-income and middle-income countries. The roles of S pyogenes skin and pharyngeal carriage in transmission are unclear. We aimed to investigate the clinical epidemiology and household transmission dynamics of both S pyogenes asymptomatic carriage and infection in a high-burden setting. METHODS: We did a 1-year prospective, longitudinal, household cohort study, recruiting healthy participants from households in Sukuta, The Gambia. Households were eligible if they comprised at least three members, including one child younger than 18 years, and were excluded if more than half of household members declined to participate. Households were identified by random GPS coordinates derived from census data. At monthly visits, pharyngeal and normal skin swabs were collected for S pyogenes culture, and sociodemographic data were recorded by interview. Incident pharyngitis and pyoderma infections were captured. Cultured isolates underwent emm genotyping. The primary outcome measures were incidence of S pyogenes carriage and disease. Additional outcomes were prevalence of S pyogenes skin and pharyngeal carriage, S pyogenes skin and pharyngeal clearance time, S pyogenes emm type, risk factors for carriage and disease events, household secondary attack rate, and emm-linked household transmission events. The study is registered on ClinicalTrials.gov, NCT05117528. FINDINGS: Between July 27, 2021, and Sept 28, 2022, 442 participants were enrolled from 44 households. The median age was 15 years (IQR 6-28) and 233 (53%) were female. We identified 17 pharyngitis and 99 pyoderma events and 49 pharyngeal and 39 skin S pyogenes carriage acquisition events. Mean monthly prevalence was 1·4% (95% CI 1·1-1·9) for S pyogenes pharyngeal carriage and 1·2% (0·9-1·6) for S pyogenes skin carriage. Incidence was 120 per 1000 person-years (95% CI 87-166) for S pyogenes pharyngeal carriage, 124 per 1000 person-years (90-170) for S pyogenes skin carriage, 51 per 1000 person-years (31-84) for S pyogenes pharyngitis, and 263 per 1000 person-years (212-327) for S pyogenes pyoderma. Pharyngeal carriage risk was higher during the rainy season (HR 5·67, 95% CI 2·19-14·69) and in larger households (per additional person: 1·03, 1·00-1·05), as was pharyngitis risk (rainy season: 3·00, 1·10-8·22; household size: 1·04, 1·02-1·07). Skin carriage risk was not affected by season or household size, but was lower in female than in male participants (0·45, 0·22-0·92) and highest in children younger than 5 years compared with adults (22·69, 3·08-167·21), with similar findings for pyoderma (female sex: 0·34, 0·19-0·61; age <5 years: 7·00, 2·78-17·64). Median clearance time after carriage acquisition was 4·0 days for both skin (IQR 3·5-7·0) and pharynx (3·5-7·3). The mean household secondary attack rate was 4·9 (95% CI 3·5-6·3) for epidemiologically linked S pyogenes events and 0·74 (0·3-1·2) for emm-linked S pyogenes events. Of the 204 carriage and disease events, emm types were available for 179 (88%). Only 18 emm-linked between-visit household transmission events were identified. Pyoderma was the most common source of S pyogenes household transmissions in 11 (61%) of 18 emm-linked transmissions. Both pharynx to skin and skin to pharynx transmission events were observed. INTERPRETATION: S pyogenes carriage and infection are common in The Gambia, particularly in children. Most events are non-household acquisitions, but skin carriage and pyoderma have an important role in S pyogenes household transmission and bidirectional transmission between skin and pharynx occurs. FUNDING: Wellcome Trust, Chadwick Trust, Fonds National de la Recherche Scientifique (Belgium), European Society for Paediatric Infectious Diseases, and Medical Research Council (UK).

Use of the "Sepsis Risk Calculator" in Belgian Newborns: A Retrospective Cohort Study.

BACKGROUND: Prevention of early-onset neonatal sepsis (EONS) is a frequent reason why many newborns receive unnecessary antibiotics. The Sepsis Risk Calculator (SRC) was developed by the Kaiser Permanente Institute as a multivariate risk assessment of EONS, aiming to reduce laboratory testing and empiric neonatal antibiotic therapy. Our objective was to assess the potential of the SRC in reducing antibiotic use in our setting. METHODS: Late preterm and term newborns who received antibiotics from 2019 to 2020 in a tertiary Belgian hospital were included. Newborn-specific data were collected and entered into the online SRC, retrospectively calculating a sepsis risk score and providing recommendations for antibiotic administration. False-positive indications for treatment by the SRC were estimated based on previously published data. Antibiotic therapy rates according to the SRC recommendations were compared to the actual rate of antibiotic therapy. RESULTS: Of 5891 births, 414 newborns received antibiotics and were eligible for this study, representing a rate of 7.6% of newborns receiving antibiotics following our current guidelines. The SRC would have recommended antibiotic administration for 2.7%, reducing antibiotic therapy by 64.5%. Of 5 possible cases of EONS, 3 would have received antibiotics in the first 24 hours according to the SRC. CONCLUSIONS: In this Belgian cohort, use of the SRC has the potential to significantly decrease by 64.5% the newborns that receive antibiotics. This reduction would primarily concern asymptomatic newborns. If use of the SRC was to be implemented in Belgian maternities, strict clinical surveillance practices should be ensured.

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.

Group A Streptococcus adaptation to diverse niches: lessons from transcriptomic studies.

Group A Streptococcus (GAS) is a major human pathogen, causing diseases ranging from mild superficial infections of the skin and pharyngeal epithelium to severe systemic and invasive diseases. Moreover, post infection auto-immune sequelae arise by a yet not fully understood mechanism. The ability of GAS to cause a wide variety of infections is linked to the expression of a large set of virulence factors and their transcriptional regulation in response to various physiological environments. The use of transcriptomics, among others -omics technologies, in addition to traditional molecular methods, has led to a better understanding of GAS pathogenesis and host adaptation mechanisms. This review focusing on bacterial transcriptomic provides new insight into gene-expression patterns in vitro, ex vivo and in vivo with an emphasis on metabolic shifts, virulence genes expression and transcriptional regulators role.

Increase in bloodstream infections caused by emm1 group A Streptococcus correlates with emergence of toxigenic M1UK, Belgium, May 2022 to August 2023.

Many European countries have recently reported upsurges in invasive group A Streptococcus (iGAS) infections, mainly caused by emm1 Streptococcus pyogenes, specifically the toxigenic M1UK lineage. We present the epidemiology of emm1 causing iGAS in Belgium during 2018-August 2023, and describe an emergence of the toxigenic M1UK lineage in Belgium in mid-2022 that was observed as an increase in bloodstream infections caused by emm1 S. pyogenes that continued into 2023.

Policies on children and schools during the SARS-CoV-2 pandemic in Western Europe.

During the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), mitigation policies for children have been a topic of considerable uncertainty and debate. Although some children have co-morbidities which increase their risk for severe coronavirus disease (COVID-19), and complications such as multisystem inflammatory syndrome and long COVID, most children only get mild COVID-19. On the other hand, consistent evidence shows that mass mitigation measures had enormous adverse impacts on children. A central question can thus be posed: What amount of mitigation should children bear, in response to a disease that is disproportionally affecting older people? In this review, we analyze the distinct child versus adult epidemiology, policies, mitigation trade-offs and outcomes in children in Western Europe. The highly heterogenous European policies applied to children compared to adults did not lead to significant measurable differences in outcomes. Remarkably, the relative epidemiological importance of transmission from school-age children to other age groups remains uncertain, with current evidence suggesting that schools often follow, rather than lead, community transmission. Important learning points for future pandemics are summarized.

Streptococcus pyogenes Colonization in Children Aged 24-59 Months in the Gambia: Impact of Live Attenuated Influenza Vaccine and Associated Serological Responses.

BACKGROUND: Immunity to Streptococcus pyogenes in high burden settings is poorly understood. We explored S. pyogenes nasopharyngeal colonization after intranasal live attenuated influenza vaccine (LAIV) among Gambian children aged 24-59 months, and resulting serological response to 7 antigens. METHODS: A post hoc analysis was performed in 320 children randomized to receive LAIV at baseline (LAIV group) or not (control). S. pyogenes colonization was determined by quantitative polymerase chain reaction (qPCR) on nasopharyngeal swabs from baseline (day 0), day 7, and day 21. Anti-streptococcal IgG was quantified, including a subset with paired serum before/after S. pyogenes acquisition. RESULTS: The point prevalence of S. pyogenes colonization was 7%-13%. In children negative at day 0, S. pyogenes was detected at day 7 or 21 in 18% of LAIV group and 11% of control group participants (P = .12). The odds ratio (OR) for colonization over time was significantly increased in the LAIV group (day 21 vs day 0 OR, 3.18; P = .003) but not in the control group (OR, 0.86; P = .79). The highest IgG increases following asymptomatic colonization were seen for M1 and SpyCEP proteins. CONCLUSIONS: Asymptomatic S. pyogenes colonization appears modestly increased by LAIV, and may be immunologically significant. LAIV could be used to study influenza-S. pyogenes interactions. Clinical Trials Registration. NCT02972957.

Promiscuous evolution of Group A Streptococcal M and M-like proteins.

Group A Streptococcus (GAS) M and M-like proteins are essential virulence factors and represent the primary epidemiological marker of this pathogen. Protein sequences encoding 1054 M, Mrp and Enn proteins, from 1668 GAS genomes, were analysed by SplitsTree4, partitioning around medoids and co-occurrence. The splits network and groups-based analysis of all M and M-like proteins revealed four large protein groupings, with multiple evolutionary histories as represented by multiple edges for most splits, leading to 'M-family-groups' (FG) of protein sequences: FG I, Mrp; FG II, M protein and Protein H; FG III, Enn; and FG IV, M protein. M and Enn proteins formed two groups with nine sub-groups and Mrp proteins formed four groups with ten sub-groups. Discrete co-occurrence of M and M-like proteins were identified suggesting that while dynamic, evolution may be constrained by a combination of functional and virulence attributes. At a granular level, four distinct family-groups of M, Enn and Mrp proteins are observable, with Mrp representing the most genetically distinct of the family-group of proteins. While M and Enn protein families generally group into three distinct family-groups, horizontal and vertical gene flow between distinct GAS strains is ongoing.

Increase in invasive group A streptococcal disease among Australian children coinciding with northern hemisphere surges.

Background: Increases in invasive group A streptococcal disease (iGAS) have recently been reported in multiple countries in the northern hemisphere, occurring during, and outside of, typical spring peaks. We report the epidemiology of iGAS among children in Australia from 1 July 2018 to 31 December 2022. Methods: The Paediatric Active Enhanced Disease Surveillance (PAEDS) Network prospectively collected iGAS patient notifications for children and young people aged less than 18 years admitted to five major Australian paediatric hospitals in Victoria, Queensland, Western Australia and the Northern Territory. Patients were eligible for inclusion if they had GAS isolated from a normally sterile body site, or met clinical criteria for streptococcal toxic shock syndrome or necrotising fasciitis with GAS isolated from a non-sterile site. We report patients' clinical and demographic characteristics, and estimate minimum incidence rates. Findings: We identified 280 paediatric iGAS patients, median age 4.5 years (interquartile range 1.4-6.4). We observed a pre-pandemic peak annualised incidence of 3.7 per 100,000 (95% CI 3.1-4.4) in the 3rd quarter of 2018, followed by a decline to less than 1.0 per 100,000 per quarter from 2020 to mid-2021. The annualised incidence increased sharply from mid-2022, peaking at 5.2 per 100,000 (95% CI 4.4-6.0) in the 3rd quarter and persisting into the 4th quarter (4.9 per 100,000, 95% CI 4.2-5.7). There were 3 attributable deaths and 84 (32%) patients had severe disease (overall case fatality rate 1%, 95% CI 0.2-3.3). Respiratory virus co-infection, positive in 57 of 119 patients tested, was associated with severe disease (RR 1.9, 95% CI 1.2-3.0). The most common emm-type was emm-1 (60 of 163 isolates that underwent emm-typing, 37%), followed by emm-12 (18%). Interpretation: Australia experienced an increase in the incidence of iGAS among children and young people in 2022 compared to pandemic years 2020-2021. This is similar to northern hemisphere observations, despite differences in seasons and circulating respiratory viruses. Outbreaks of iGAS continue to occur widely. This emphasises the unmet need for a vaccine to prevent significant morbidity associated with iGAS disease. Funding: Murdoch Children's Research Institute funded open access publishing of this manuscript.

Evaluation of a surgical treatment algorithm for neglected clubfoot in low-resource settings.

PURPOSE: Idiopathic clubfoot affects approximately 1/1000 alive-born infants, of whom 80-91% are born in low- or middle-income countries (LMICs). This retrospective study aimed to evaluate the morphological, functional, and social outcomes in patients with neglected clubfoot in rural Bangladesh, after receiving surgical treatment. METHODS: Patients received a posteromedial release (PMR) with or without an additional soft tissue intervention (group 1), a PMR with an additional bony intervention (group 2), or a triple arthrodesis (group 3) according to our surgical algorithm. Patients were followed until two year post-intervention. Evaluation was done using a modified International Clubfoot Study Group Outcome evaluation score and the Laaveg-Ponseti score. RESULTS: Twenty-two patients with 32 neglected clubfeet (ages 2-24 years) received surgical treatment. Nineteen patients with 29 clubfeet attended follow-up. At two year follow-up an excellent, good, or fair Laaveg-Ponseti score was obtained in 81% (group 1), 80% (group 2), and 0% (group 3) of the patients (p value 0.0038). Age at intervention is inversely correlated with the Laaveg-Ponseti score at two year follow-up (p < 0.0001). All patients attended school or work and were able to wear normal shoes. CONCLUSION: Our treatment algorithm is in line with other surgical algorithms used in LMICs. Our data reconfirms that excellent results can be obtained with a PMR regardless of age. Our algorithm follows a pragmatic approach that takes into account the reality on the ground in many LMICs. Good functional outcomes can be achieved with PMR for neglected clubfoot. Further research is needed to investigate the possible role of triple arthrodesis.

Invasive Group A Streptococcal Infections: Benefit of Clindamycin, Intravenous Immunoglobulins and Secondary Prophylaxis.

Introduction: Mortality associated with invasive group A streptococcal infections (iGAS) remains high among adults, with lower mortality in children. The added value of both clindamycin and immunoglobulins in such treatment is still controversial, as is the need for antibiotic secondary prophylaxis. It is unlikely that conclusive randomized clinical studies will ever definitively end these controversies. Materials and Methods: A clinical and experimental literature review was conducted in Pubmed, Cochrane, and lay literature to determine the benefit of adding clindamycin and immunoglobulins to ß-lactams in the management of iGAS, as well as the need for secondary prophylaxis measures in close contacts. Results: This review includes two meta-analyses, two randomized controlled trials, four prospective studies, five retrospective studies, and microbiological studies. To reduce mortality and morbidity, it appears useful to add clindamycin to ß-lactams in severe clinical presentations, including necrotizing fasciitis or streptococcal toxic shock syndrome, and immunoglobulins for the latter two presentations. The high risk of secondary infection in household contacts justifies the need of taking preventive measures. Conclusions: Both clinical studies and available experimental evidence suggest that adding clindamycin and immunoglobulins as adjunctive therapies in the management of invasive group A streptococcal infections may reduce mortality. Household contacts should be warned about the increased risk of secondary infection, and chemoprophylaxis may be considered in certain situations.

Improvement of Rheumatic Valvular Heart Disease in Patients Undergoing Prolonged Antibiotic Prophylaxis.

Secondary prophylaxis of rheumatic heart diseases is efficient in reducing disease recurrence, heart damage, and cardiac impairment. We aimed to monitor the clinical evolution of a large Brazilian cohort of rheumatic patients under prolonged secondary prophylaxis. From 1986 to 2018, a cohort of 593 patients with rheumatic fever was followed every 6 months by the Reference Center for the Control and Prevention of Rheumatic Fever and Rheumatic Cardiopathy (CPCFR), Paraná, Brazil. In this cohort, 243 (41%) patients did not present cardiac damage (group I), while 350 (59%) were diagnosed with rheumatic heart disease (RHD) (group II) using the latest case definition. Among group II, 233 and 15 patients had impairment of the mitral and aortic valves, respectively, while 102 patients had impairment of both valves. Lesions on the mitral and aortic valves presented a regression in 69.9 and 48.7% of the patients, respectively. Active patient recruitment in the reference center and early detection of oropharyngeal GAS were important factors for optimal adherence to the prophylactic treatment. Patients with disease progression were associated with noncompliance to secondary prophylaxis. No patients undergoing regular prophylaxis presented progression of the rheumatic cardiac disease. Eighteen valvular surgeries were performed, and four (0.7%) patients died. This study confirmed that tailored and active efforts invested in rheumatic heart disease secondary prevention allowed for significant clinical improvement.

An emm-type specific qPCR to track bacterial load during experimental human Streptococcus pyogenes pharyngitis.

BACKGROUND: Streptococcus pyogenes causes a profound global burden of morbidity and mortality across its diverse clinical spectrum. To support a new controlled human infection ('challenge') model seeking to accelerate S. pyogenes vaccine development, we aimed to develop an accurate and reliable molecular method for quantifying bacterial load from pharyngeal swabs collected during experimental human pharyngitis. METHODS: Combined sequential RNA + DNA extraction from throat swabs was compared to traditional separate RNA-only and DNA-only extractions. An emm-type specific qPCR was developed to detect the emm75 challenge strain. Results from the qPCR were compared to culture, using throat swab samples collected in a human challenge study. RESULTS: The qPCR was 100% specific for the emm75 challenge strain when tested against a panel of S. pyogenes emm-types and other respiratory pathogens. Combined RNA + DNA extraction had similar yield to traditional separate extractions. The combined extraction method and emm75 qPCR had 98.8% sensitivity compared to culture for throat swabs collected from challenge study participants. CONCLUSIONS: We have developed a reliable molecular method for measuring S. pyogenes bacterial load from throat swabs collected in a controlled human infection model of S. pyogenes pharyngitis. TRIAL REGISTRATION: NCT03361163 on 4th December 2017.

Diagnostic accuracy of rapid nucleic acid tests for group A streptococcal pharyngitis: systematic review and meta-analysis.

BACKGROUND: Acute pharyngitis is one of the most common conditions in outpatient settings and an important source of inappropriate antibiotic prescribing. Rapid antigen detection tests (RADTs) offer diagnosis of group A streptococcus at the point of care but have limited sensitivity. Rapid nucleic acid tests (RNATs) are now available; a systematic review of their accuracy is lacking. OBJECTIVES: To evaluate the accuracy of RNATs in patients with pharyngitis; to explore test-level and study-level factors that could explain variability in accuracy; and to compare the accuracy of RNATs with that of RADTs. DATA SOURCES: MEDLINE, Embase, Web of Science (1990-2020). STUDY ELIGIBILITY CRITERIA: Cross-sectional studies and randomized trials. PARTICIPANTS: Patients with pharyngitis. INDEX TEST/S AND REFERENCE STANDARDS: RNAT commercial kits compared with throat culture. METHODS: We assessed risk of bias and applicability using QUADAS-2. We performed meta-analysis of sensitivity and specificity using the bivariate random-effects model. Variability was explored by subgroup analyses and meta-regression. RESULTS: We included 38 studies (46 test evaluations; 17 411 test results). RNATs were most often performed in a laboratory. The overall methodological quality of primary studies was uncertain because of incomplete reporting. RNATs had a summary sensitivity of 97.5% (95% CI 96.2%-98.3%) and a summary specificity of 95.1% (95% CI 93.6%-96.3%). There was low variability in estimates across studies. Variability in sensitivity and specificity was partially explained by test type (p < 0.05 for both). Sensitivity analyses limited to studies with low risk of bias showed robust accuracy estimates. RNATs were more sensitive than RADTs (13 studies; 96.8% versus 82.3%, p 0.004); there was no difference in specificity (p 0.92). CONCLUSIONS: The high diagnostic accuracy of RNATs may allow their use as stand-alone tests to diagnose group A streptococcus pharyngitis. Based on direct comparisons, RNATs have greater sensitivity than RADTs and equal specificity. Further studies should evaluate RNATs in point-of-care settings.

Molecular Epidemiology of Group A Streptococcus Infections in The Gambia.

Molecular epidemiological data on Group A Streptococcus (GAS) infection in Africa is scarce. We characterized the emm-types and emm-clusters of 433 stored clinical GAS isolates from The Gambia collected between 2004 and 2018. To reduce the potential for strain mistyping, we used a newly published primer for emm-typing. There was considerable strain diversity, highlighting the need for vaccine development offering broad strain protection.

Serological Profiling of Group A Streptococcus Infections in Acute Rheumatic Fever.

Rheumatic fever is a serious post-infectious sequela of group A Streptococcus (GAS). Prior GAS exposures were mapped in sera using a large panel of M-type specific peptides. Rheumatic fever patients had serological evidence of significantly more GAS exposures than matched controls suggesting immune priming by repeat infections contributes to pathogenesis.

A controlled human infection model of Streptococcus pyogenes pharyngitis (CHIVAS-M75): an observational, dose-finding study.

BACKGROUND: Streptococcus pyogenes is a leading cause of infection-related morbidity and mortality. A reinvigorated vaccine development effort calls for new clinically relevant human S pyogenes experimental infection models to support proof of concept evaluation of candidate vaccines. We describe the initial Controlled Human Infection for Vaccination Against S pyogenes (CHIVAS-M75) study, in which we aimed to identify a dose of emm75 S pyogenes that causes acute pharyngitis in at least 60% of volunteers when applied to the pharynx by swab. METHODS: This observational, dose-finding study was done in a clinical trials facility in Melbourne (VIC, Australia). Groups of healthy volunteers aged 18-40 years, at low risk of complicated S pyogenes disease, and without high type-specific anti-emm75 IgG antibodies against the challenge strain were challenged and closely monitored as inpatients for up to 6 days, and then as outpatients for 6 months. Antibiotics were started upon diagnosis (clinical signs and symptoms of pharyngitis and a positive rapid molecular test) or after 5 days in those without pharyngitis. Rapid test results were confirmed by standard bacterial culture. After a sentinel participant, cohorts of five and then ten participants were challenged, with protocol-directed dose-escalation or de-escalation for subsequent cohorts. The primary outcome was the proportion of participants at each dose level with pharyngitis by day 5 after challenge. The study is registered with ClinicalTrials.gov, NCT03361163. FINDINGS: Between July 10, 2018, and Sept 23, 2019, 25 healthy adults were challenged with emm75 S pyogenes and included in analyses. Pharyngitis was diagnosed in 17 (85%; 95% CI 62-97) of 20 participants at the starting dose level (1-3 × 105 colony-forming units [CFU]/mL). This high proportion prompted dose de-escalation. At the lower dose level (1-3 × 104 CFU/mL), pharyngitis was diagnosed in one of five participants. Immunological, biochemical, and microbiological results supported the clinical picture, with acute symptomatic pharyngitis characterised by pharyngeal colonisation by S pyogenes accompanied by significantly elevated C-reactive protein and inflammatory cytokines (eg, interferon-γ and interleukin-6), and modest serological responses to streptolysin O and deoxyribonuclease B. There were no severe (grade 3) or serious adverse events related to challenge. INTERPRETATION: We have established a reliable pharyngitis human infection model with reassuring early safety findings to accelerate development of vaccines and other interventions to control disease due to S pyogenes. FUNDING: Australian National Health and Medical Research Council.