Frequency of transmission, asymptomatic shedding, and airborne spread of Streptococcus pyogenes in schoolchildren exposed to scarlet fever: a prospective, longitudinal, multicohort, molecular epidemiological, contact-tracing study in England, UK

Contact tracing strategies for infectious diseases: A systematic literature review

Contact tracing has been a crucial public health strategy for breaking infectious diseases chains of transmission. Although many resources exist for disease outbreak management none address the rationale of contact tracing. This comprehensive review aims to evaluate contact tracing strategies, their effectiveness, and health systems governance across various diseases to inform a disease-agnostic contact tracing guideline. This systematic review was registered with PROSPERO (ID: CRD42023474507) and follows Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Descriptive and interventional studies in the six official United Nations languages were included, excluding modelling studies and animal-to-human transmission. An electronic search was conducted in Embase, Medline, Medline-in-process, and Cochrane libraries from inception to September 2023. The revised Cochrane Risk of Bias Tool and the Risk of Bias in Non-Randomized Studies of Interventions were used for bias assessment. The search yielded 378 studies, primarily from Europe (29.6%) and North America (21.6%) and focusing on diseases such as the coronavirus disease (COVID-19) (47.4%) or tuberculosis (26.7%). 244 (64.5%) studies addressed contact tracing definitions, commonly based on physical proximity, including duration of contact and sexual partnerships (47.6%) and household exposure (27%). Effectiveness was examined in 330 (87.3%) studies, showing variation across diseases and contexts, with only five studies evaluating epidemiological impacts. Socio-cultural aspects were covered in 166 (43.9%) studies, revealing that stigma and public trust may affect the adherence to contact tracing. Health systems governance was discussed in 278 (73.5%) studies, emphasising the need for coordination among international organisations, national governments, and local health authorities, alongside a sustained and adequately supported workforce. This review provides critical insights into optimising contact tracing strategies. Effective contact tracing requires robust health systems governance, adequate resources, and community involvement. Future research should focus on establishing standardised metrics for comparative analysis and investigating the impact of contact tracing on disease incidence and mortality.

The application of environmental health assessment strategies to detect Streptococcus pyogenes in Kimberley school classrooms

BACKGROUND

Children spend almost one-third of their waking hours at school. Streptococcus pyogenes (Strep A) is a common childhood bacterial infection that can progress to causing serious disease. We aimed to detect Strep A in classrooms by using environmental settle plates and swabbing of high-touch surfaces in two remote schools in the Kimberley, Western Australia.

METHODS

Twelve classrooms in two schools participated in 2021 and 2022. Seven horse-blood agar plates containing colistin and nalidixic acid (HBA-CNA) were placed in each occupied classroom at varied heights for 4 h, and 20 high-touch items were swabbed and later cultured on HBA-CNA plates. The primary outcome of each sample was presence or absence of Strep A. Identified Strep A isolates were whole genome sequenced (WGS) to assess for similarity between host-derived and environmental strains.

RESULTS

During two visits to each participating Kimberley school in June 2021 and September 2022, the point prevalence of Strep A positive throat swab ranged between 3/34 (8.8 %) and 5/21 (23.8 %); Strep A impetigo was lower at between 0/43 (0 %) and 2/23 (8.7 %). Strep A was detected from 4/240 (2 %) environmental swabs collected across 3/12 (25 %) classrooms but not cultured from any of the classroom settle plates. Whole genome sequencing identified environmental emm types to also be those strains in circulation.

CONCLUSIONS

There was little evidence to support fomite, droplet or airborne Strep A in classrooms as major modes of transmission among children. Further work is required to determine if classrooms play a role in the transmission of Strep A between students.

Antibiotic chemoprophylaxis for close contacts of invasive group A streptococcus in community settings: Evidence review

OBJECTIVES

Revised UK guidelines for the management of contacts of invasive group A Streptococcus (iGAS) infection in community settings were published in December 2022. We present the findings of a narrative review which informed the public health recommendations around the provision of antibiotic chemoprophylaxis detailed in the updated guidelines.

METHODS

We conducted a literature review of studies reporting the risk of iGAS infection associated with specific risk factors.

RESULTS

There was strong epidemiological evidence for an increased risk of iGAS infection in contacts who are older individuals, post-partum women, neonates and individuals with chickenpox infection; evidence on the impact of influenza co-infection, injecting drug use or being homeless in increasing risk of iGAS infection was less robust.

CONCLUSIONS

The guidelines made recommendations to offer chemoprophylaxis to close contacts of iGAS cases who are aged ≥75 years, pregnant ≥37 weeks gestation, post-partum, neonates or those with a recent history of, or current chickenpox infection. Systematic data collection evaluating the use of chemoprophylaxis and other control measures is recommended.

A Striking Increase in Carriage Among Young Children in Iceland Paralleled the Unprecedented Increase of Invasive Group A Streptococcal Infection From 2022 to 2023

BACKGROUND

An unprecedented increase in pediatric invasive group A streptococcal (iGAS) infections was observed in most countries, including Iceland, in early 2023. The reasons for this rise are largely unknown. The aim of the study was to describe the parallel between nasopharyngeal (NP) carriage of group A streptococcal (GAS) in Icelandic children and the incidence of invasive disease.

METHODS

Electronic health records were used to identify children admitted to the Children's Hospital, Iceland, with iGAS. NP samples from asymptomatic children were collected for culture in February and March 2023 in 15 day-care centers in the greater Reykjavik area. Invasive and noninvasive isolates were characterized using whole genome sequencing. The results of the NP carriage were compared with data from 2009 to 2020.

RESULTS

Twenty-one children were diagnosed with iGAS from December 2022 to April 2023. Empyema, necrotizing fasciitis and septic or toxic shock were the most common clinical presentations. All the children were hospitalized; none died, but 9 needed intensive care. Pediatric iGAS infections increased 8-fold from a mean of 2.0/100.000 for 1975 to 2022 to 16.5/100.000 in early 2023. Asymptomatic NP GAS carriage among healthy children increased 3.5-fold from 8.0% from 2009 to 2020 to 28.5% in early 2023. Close genetic relatedness was found between carriage and invasive strains.

CONCLUSIONS

The significant rise of NP GAS carriage observed in early 2023 likely contributed to the simultaneous increased incidence of iGAS. With surveillance data, microbiological culture and molecular typing, genetic similarities between invasive disease isolates and NP isolates characteristics were confirmed.

Prevalence of Asymptomatic Group A Streptococcus Carriage Based on Rapid Antigen Detection Test in Healthy Adults in Poland

Background: Acute pharyngitis is one of the most prevalent disorders seen in general practitioners' consultations. Most cases of acute pharyngitis in adults are caused by respiratory viruses and are self-limited. However, clinical manifestations of viral pharyngitis can overlap with bacterial pharyngitis, mainly caused by group A Streptococcus (GAS). A rapid antigen test for GAS can help diagnose streptococcal pharyngitis, but misdiagnosing S. pyogenes infection in a patient with a viral condition can lead to inappropriate antibiotic use. Some patients with a sore throat due to a virus or other causes will test positive for GAS because of carriage. The aim of our study was to analyze rapid strep test results in healthy adults. Methods: A cohort study was conducted in an outpatient clinic in Wroclaw. We used the rapid strep test BIOSYNEX STREP A. Results: A total of 350 healthy volunteers (≥18 years old) were enrolled in this study. The presence of Streptococcus pyogenes, based on a rapid strep test, was detected in 17 adults (4.9%). The strep test positivity rate was higher in younger adults. Conclusions: In healthy individuals in Poland, the prevalence of pharyngeal carriage of GAS is 4.9%. This finding emphasizes that the rapid antigen detection test should only be used in cases of suspected bacterial pharyngitis to avoid inappropriate antibiotic use.

Recent Advances on the Prevention and Management of Rheumatic Heart Disease

The global burden of rheumatic heart disease (RHD) remains substantial, particularly in low-income countries, despite advancements in prevention and management strategies. This article emphasizes the strategies related to primordial prevention, primary prevention, and secondary prevention, including recent advancements in vaccine development, and discusses current challenges in management and future research directions. For treatment, it evaluates percutaneous mitral commissurotomy, mitral valve repair, and replacement, noting the advantages of individualized approaches based on patient conditions. Addressing RHD's global burden requires equitable access to surgical treatments, robust healthcare systems, and sustainable strategies for prevention and care.

The effect of pathogens from environmental breeding and accumulative release by the infected individuals on spread dynamics of a SIRP epidemic model

In this paper, a SIRP epidemic model is proposed, wherein the pathogens derive from two ways, i.e., environmental breeding, and accumulative excretion by the infected individuals. The former is characterized by Logistic growth, while the latter is in the form of infinite integral. First, the positivity and ultimate boundedness of solutions are obtained. Second, the basic reproduction number R 0 is obtained, by which the model is analyzed if either the intrinsic growth rate of environmental pathogens is lower or higher than its clearance rate. For the first case, the disease-free equilibrium is globally asymptotically stable whenR 0 < 1 , while the endemic equilibrium is globally asymptotically stable whenR 0 > 1 . Conversely, if the growth rate exceeds the removal rate, the disease-free equilibrium is always unstable, meanwhile, the uniform persistence of the model indicates that there could exist one or multi-endemic equilibria, and it is globally asymptotically stable if the endemic equilibrium is unique. Finally, the theoretical results are illustrated by numerical simulations. We find that the accumulative release of pathogens by the infected individuals in the form of infinite integral is more realistic and consistent with the disease spread than that of linear form by real data.

The intricate pathogenicity of Group A Streptococcus: A comprehensive update

Group A Streptococcus (GAS) is a versatile pathogen that targets human lymphoid, decidual, skin, and soft tissues. Recent advancements have shed light on its airborne transmission, lymphatic spread, and interactions with neuronal systems. GAS promotes severe inflammation through mechanisms involving inflammasomes, IL-1β, and T-cell hyperactivation. Additionally, it secretes factors that directly induce skin necrosis via Gasdermin activation and sustains survival and replication in human blood through sophisticated immune evasion strategies. These include lysis of erythrocytes, using red cell membranes for camouflage, resisting antimicrobial peptides, evading phagocytosis, escaping from neutrophil extracellular traps (NETs), inactivating chemokines, and cleaving targeted antibodies. GAS also employs molecular mimicry to traverse connective tissues undetected and exploits the host's fibrinolytic system, which contributes to its stealth and potential for causing autoimmune conditions after repeated infections. Secreted toxins disrupt host cell membranes, enhancing intracellular survival and directly activating nociceptor neurons to induce pain. Remarkably, GAS possesses mechanisms for precise genome editing to defend against phages, and its fibrinolytic capabilities have found applications in medicine. Immune responses to GAS are paradoxical: robust responses to its virulence factors correlate with more severe disease, whereas recurrent infections often show diminished immune reactions. This review focuses on the multifaceted virulence of GAS and introduces novel concepts in understanding its pathogenicity.

Chains of misery: surging invasive group A streptococcal disease

PURPOSE OF REVIEW

We describe the epidemiology of the recent global surge in invasive group A streptococcal (GAS) disease and consider its proximate and distal causes. We highlight important knowledge gaps regarding clinical management and discuss potential strategies for prevention.

RECENT FINDINGS

Rates of invasive GAS (iGAS) disease were increasing globally prior to the COVID-19 pandemic. Since mid-2022, following the worst years of the pandemic in 2020 and 2021, many countries with systems to monitor GAS syndromes have reported surges in cases of iGAS concurrent with increased scarlet fever, pharyngitis, and viral co-infections. The emergence of the hypervirulent M1 UK strain as a cause of iGAS, particularly in high income countries, is concerning. New data are emerging on the transmission dynamics of GAS. GAS remains universally susceptible to penicillin but there are increasing reports of macrolide and lincosamide resistance, particularly in invasive isolates, with uncertain clinical consequences. Intravenous immunoglobulin is used widely for streptococcal toxic shock syndrome and necrotizing soft tissue infections, although there is limited clinical evidence, and none from a completed randomized controlled trial. Intensive and expensive efforts at population-level control of GAS infections and postinfectious autoimmune complications have been only partially successful. The great hope for control of GAS diseases remains vaccine development. However, all modern vaccine candidates remain in the early development stage.

SUMMARY

In many countries, iGAS rates surged from mid-2022 in the aftermath of pandemic control measures and physical distancing. The emergence of a dominant hypervirulent strain is an important but incomplete explanation for this phenomenon. Clinical management of iGAS remains highly empirical and new data has not emerged. A vaccine remains the most likely means of achieving a sustainable reduction in the burden of iGAS.

Genomic cluster formation among invasive group A streptococcal infections in the USA: a whole-genome sequencing and population-based surveillance study

BACKGROUND

Clusters of invasive group A streptococcal (iGAS) infection, linked to genomically closely related group A streptococcal (GAS) isolates (referred to as genomic clusters), pose public health threats, and are increasingly identified through whole-genome sequencing (WGS) analysis. In this study, we aimed to assess the risk of genomic cluster formation among iGAS cases not already part of existing genomic clusters.

METHODS

In this WGS and population-based surveillance study, we analysed iGAS case isolates from the Active Bacterial Core surveillance (ABCs), which is part of the US Centers for Disease Control and Prevention's Emerging Infections Program, in ten US states from Jan 1, 2015, to Dec 31, 2019. We included all residents in ABCs sites with iGAS infections meeting the case definition and excluded non-conforming GAS infections and cases with whole-genome assemblies of the isolate containing fewer than 1·5 million total bases or more than 150 contigs. For iGAS cases we collected basic demographics, underlying conditions, and risk factors for infection from medical records, and for isolates we included emm types, antimicrobial resistance, and presence of virulence-related genes. Two iGAS cases were defined as genomically clustered if their isolates differed by three or less single-nucleotide variants. An iGAS case not clustered with any previous cases at the time of detection, with a minimum trace-back time of 1 year, was defined as being at risk of cluster formation. We monitored each iGAS case at risk for a minimum of 1 year to identify any cluster formation event, defined as the detection of a subsequent iGAS case clustered with the case at risk. We used the Kaplan-Meier method to estimate the cumulative incidence of cluster formation events over time. We used Cox regression to assess associations between features of cases at risk upon detection and subsequent cluster formation. We developed a random survival forest machine-learning model based on a derivation cohort (random selection of 50% of cases at risk) to predict cluster formation risk. This model was validated using a validation cohort consisting of the remaining 50% of cases at risk.

FINDINGS

We identified 2764 iGAS cases at risk from 2016 to 2018, of which 656 (24%) formed genomic clusters by the end of 2019. Overall, the cumulative incidence of cluster formation was 0·057 (95% CI 0·048-0·066) at 30 days after detection, 0·12 (0·11-0·13) at 90 days after detection, and 0·16 (0·15-0·18) at 180 days after detection. A higher risk of cluster formation was associated with emm type (adjusted hazard ratio as compared with emm89 was 2·37 [95% CI 1·71-3·30] for emm1, 2·72 [1·82-4·06] for emm3, 2·28 [1·49-3·51] for emm6, 1·47 [1·05-2·06] for emm12, and 2·21 [1·38-3·56] for emm92), homelessness (1·42 [1·01-1·99]), injection drug use (2·08 [1·59-2·72]), residence in a long-term care facility (1·78 [1·29-2·45]), and the autumn-winter season (1·34 [1·14-1·57]) in multivariable Cox regression analysis. The machine-learning model stratified the validation cohort (n=1382) into groups at low (n=370), moderate (n=738), and high (n=274) risk. The 90-day risk of cluster formation was 0·03 (95% CI 0·01-0·05) for the group at low risk, 0·10 (0·08-0·13) for the group at moderate risk, and 0·21 (0·17-0·25) for the group at high risk. These results were consistent with the cross-validation outcomes in the derivation cohort.

INTERPRETATION

Using population-based surveillance data, we found that pathogen, host, and environment factors of iGAS cases were associated with increased likelihood of subsequent genomic cluster formation. Groups at high risk were consistently identified by a predictive model which could inform prevention strategies, although future work to refine the model, incorporating other potential risk factors such as host contact patterns and immunity to GAS, is needed to improve its predictive performance.

FUNDING

Centers for Disease Control and Prevention.

Transmission potential of Streptococcus pyogenes during a controlled human infection trial of pharyngitis

Controlled human infection (CHI) models can provide insights into transmission of pathogens such as Streptococcus pyogenes (Strep A). As part of the Controlled Human Infection with Penicillin for Streptococcus pyogenes (CHIPS) trial, we explored the potential for transmission among participants deliberately infected with the Strep A emm75 strain. Three approaches to understanding transmission were employed: the use of agar settle plates to capture possible droplet or airborne spread of Strep A; measurement of distance droplets could spread during conversation; and environmental swabbing of high-touch items to detect Strep A on surfaces. Of the 60 (27%) CHIPS trial participants across five cohorts, 16 were enrolled in this sub-study; availability of study staff was the primary reason for selection. In total, 189 plates and 260 swabs were collected. Strep A was grown on one settle plate from a participant on the second day, using plates placed 30 cm away. This participant received the placebo dose of penicillin and had met the primary endpoint of pharyngitis. Whole-genome sequencing identified this to be the challenge strain. Strep A was not detected on any swabs. In this small sample of CHI participants, we did not find evidence of Strep A transmission by the airborne route or fomites, and just one instance of droplet spread while acutely symptomatic with streptococcal pharyngitis. Although these experiments provide evidence of minimal transmission within controlled clinical settings, greater efforts are required to explore Strep A transmission in naturalistic settings.IMPORTANCEStreptococcus pyogenes remains a significant driver of morbidity and mortality, particularly in under-resourced settings. Understanding the transmission modalities of this pathogen is essential to ensuring the success of prevention methods. This proposed paper presents a nascent attempt to determine the transmission potential of Streptococcus pyogenes nested within a larger controlled human infection model.

Pediatric acute-onset neuropsychiatric syndrome and pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections: a delphi study and consensus document about definition, diagnostic criteria, treatment and follow-up

Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal Infections (PANDAS) and Pediatric Acute-onset Neuropsychiatric Syndrome (PANS) are broad diagnoses that encompass a range of sudden-onset neuropsychiatric symptoms in children, which can include obsessive-compulsive disorder (OCD), tics, anxiety, emotional instability, and cognitive difficulties. Unlike PANDAS, PANS is not strictly linked to group A streptococcal infections but can be triggered by various infectious or environmental factors. Lights and shadows remain upon the management of children with PANS and PANDAS and there is no clear consensus regarding definition, diagnostic criteria, treatment, and follow-up. The aim of the present study was to evaluate the level of agreement on PANS and PANDAS definition, diagnostic criteria, treatment and follow-up and to assess on the basis of recent studies whether there is a need to modify the current recommendations used by primary care pediatricians and hospital pediatricians in clinical practice in order to improve outcomes. Using the Delphi method, this consensus provides shared indications on PANS and PANDAS management in pediatric age, based on the most updated literature. This work represents, in our opinion, the most complete and up-to-date information on the diagnosis of PANS and PANDAS, as well as consensus statements about several aspects of clinical care. Undoubtedly, more randomized and controlled trials are needed in the pediatric population to better define the best management, also in terms of adequate follow-up examinations and period of observation.

Systematic Review of Household Transmission of Strep A: A Potential Site for Prevention That Has Eluded Attention

BACKGROUND

Although Streptococcus pyogenes (Strep A) is the sixth-most common infectious disease globally, its transmission within the household remains an understudied driver of infection. We undertook a systematic review to better understand the transmission of Strep A among people within the home, while highlighting opportunities for prevention.

METHODS

A search strategy was applied to 5 databases between September 2022 and March 2023. Results were limited to articles published between January 2000 and March 2023. Texts were reviewed by 2 authors and the following data extracted: article details (title, author, year), study type, transmission year, country, participant age, infection status, molecular testing, and transmission mode. Funding was provided by the Australian National Health and Medical Research Council (GNT2010716).

RESULTS

The final analysis comprised 28 texts. Only 7 studies (25.0%) provided sufficient detail to identify the Strep A transmission mode: contact (n = 4), vehicle (bedding, clothing, other fabric, and medical equipment; n = 2), and contact with animals (n = 1). All others were classified as household (specific mode unascertainable). Most articles reported outbreaks involving invasive Strep A infections.

CONCLUSIONS

There is limited literature regarding household transmission of Strep A. Understanding transmission in this setting remains imperative to guide control methods.

Housing Initiatives to Address Strep A Infections and Reduce RHD Risks in Remote Indigenous Communities in Australia

Group A Streptococcus (Strep A) skin infections (impetigo) can contribute to the development of acute rheumatic fever (ARF) and rheumatic heart disease (RHD). This is of particular concern for Indigenous residents of remote communities, where rates of ARF and RHD are much higher than their urban and non-Indigenous counterparts. There are three main potential Strep A transmission pathways: skin to skin, surface to skin, and transmission through the air (via droplets or aerosols). Despite a lack of scientific certainty, the physical environment may be modified to prevent Strep A transmission through environmental health initiatives in the home, identifying a strong role for housing. This research sought to provide an outline of identified household-level environmental health initiatives to reduce or interrupt Strep A transmission along each of these pathways. The identified initiatives addressed the ability to wash bodies and clothes, to increase social distancing through improving the livability of yard spaces, and to increase ventilation in the home. To assist with future pilots and evaluation, an interactive costing tool was developed against each of these initiatives. If introduced and evaluated to be effective, the environmental health initiatives are likely to also interrupt other hygiene-related infections.

Fifteen-minute consultation: Group A streptococcal pharyngitis, diagnosis and treatment in children

Group A streptococcus (GAS) is the most common bacterial cause of pharyngitis in children. GAS causes significant suppurative and non-suppurative complications including invasive GAS disease and acute rheumatic fever. This article describes the current epidemiology and clinical presentation of GAS pharyngitis and explores how diagnostic and treatment decisions differ globally. Several key decision support tools are discussed including international guidelines, clinical decision scores and laboratory tests along with the evidence for treatment choice and duration. With recent international reports describing an increase in GAS infections, clinicians should be familiar with their local GAS pharyngitis guidelines and the rationale for diagnosis and treatment of this common childhood illness.

Epidemiology and Management of Pediatric Group A Streptococcal Pneumonia With Parapneumonic Effusion: An Observational Study

BACKGROUND

During autumn/winter 2022, UK pediatricians reported an unseasonal increase in invasive group A streptococcal infections; a striking proportion presenting with pneumonia with parapneumonic effusion.

METHODS

Clinicians across the United Kingdom were requested to submit pseudonymized clinical data using a standardized report form for children (<16 years) admitted between September 30, 2022 and February 17, 2023, with microbiologically confirmed group A streptococcal pneumonia with parapneumonic effusion.

RESULTS

From 185 cases submitted, the median patient age was 4.4 years, and 163 (88.1%) were previously healthy. Respiratory viral coinfection was detected on admission for 101/153 (66.0%) children using extended respiratory pathogen polymerase chain reaction panel. Molecular testing was the primary method of detecting group A streptococcus on pleural fluid (86/171; 50.3% samples). Primary surgical management was undertaken in 171 (92.4%) children; 153/171 (89.4%) had pleural drain inserted (96 with fibrinolytic agent), 14/171 (8.2%) had video-assisted thoracoscopic surgery. Fever duration after admission was prolonged (median, 12 days; interquartile range, 9-16). Intravenous antibiotic courses varied in length (median, 14 days; interquartile range, 12-21), with many children receiving multiple broad-spectrum antibiotics, although evidence for additional bacterial infection was limited.

CONCLUSIONS

Most cases occurred with viral coinfection, a previously well-recognized risk with influenza and varicella zoster, highlighting the need to ensure routine vaccination coverage and progress on vaccines for other common viruses (eg, respiratory syncytial virus, human metapneumovirus) and for group A streptococcus. Molecular testing is valuable to detect viral coinfection and confirm invasive group A streptococcal diagnosis, expediting the incorporation of cases into national reporting systems. Range and duration of intravenous antibiotics administered demonstrated the need for research on the optimal duration of antimicrobials and improved stewardship.

Molecular characterization of Streptococcus pyogenes (StrepA) non-invasive isolates during the 2022-2023 UK upsurge

At the end of 2022 into early 2023, the UK Health Security Agency reported unusually high levels of scarlet fever and invasive disease caused by Streptococcus pyogenes (StrepA or group A Streptococcus). During this time, we collected and genome-sequenced 341 non-invasive throat and skin S. pyogenes isolates identified during routine clinical diagnostic testing in Sheffield, a large UK city. We compared the data with that obtained from a similar collection of 165 isolates from 2016 to 2017. Numbers of throat-associated isolates collected peaked in early December 2022, reflecting the national scarlet fever upsurge, while skin infections peaked later in December. The most common emm-types in 2022-2023 were emm1 (28.7 %), emm12 (24.9 %) and emm22 (7.7 %) in throat and emm1 (22 %), emm12 (10 %), emm76 (18 %) and emm49 (7 %) in skin. While all emm1 isolates were the M1UK lineage, the comparison with 2016-2017 revealed diverse lineages in other emm-types, including emm12, and emergent lineages within other types including a new acapsular emm75 lineage, demonstrating that the upsurge was not completely driven by a single genotype. The analysis of the capsule locus predicted that only 51 % of throat isolates would produce capsule compared with 78% of skin isolates. Ninety per cent of throat isolates were also predicted to have high NADase and streptolysin O (SLO) expression, based on the promoter sequence, compared with only 56% of skin isolates. Our study has highlighted the value in analysis of non-invasive isolates to characterize tissue tropisms, as well as changing strain diversity and emerging genomic features which may have implications for spillover into invasive disease and future S. pyogenes upsurges.

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).

Rapid expansion and international spread of M1UK in the post-pandemic UK upsurge of Streptococcus pyogenes

The UK observed a marked increase in scarlet fever and invasive group A streptococcal infection in 2022 with severe outcomes in children and similar trends worldwide. Here we report lineage M1UK to be the dominant source of invasive infections in this upsurge. Compared with ancestral M1global strains, invasive M1UK strains exhibit reduced genomic diversity and fewer mutations in two-component regulator genes covRS. The emergence of M1UK is dated to 2008. Following a bottleneck coinciding with the COVID-19 pandemic, three emergent M1UK clades underwent rapid nationwide expansion, despite lack of detection in previous years. All M1UK isolates thus-far sequenced globally have a phylogenetic origin in the UK, with dispersal of the new clades in Europe. While waning immunity may promote streptococcal epidemics, the genetic features of M1UK point to a fitness advantage in pathogenicity, and a striking ability to persist through population bottlenecks.

Detection of toxigenic M1UK lineage group A Streptococcus clones in Taiwan

BACKGROUND

A new sublineage of emm1 group A Streptococcus (GAS), M1UK, has emerged in Europe, North America, and Australia. Notably, a significant portion of emm1 isolates in Asia, particularly in Hong Kong and mainland China, acquired scarlet fever-associated prophages following the 2011 Hong Kong scarlet fever outbreak. However, the presence of the M1UK sublineage has not yet been detected in Asia.

METHODS

This study included 181 GAS isolates (2011-2021). The emm type of these isolates were determined, and 21 emm1 isolates from blood or pleural fluid (2011-2021) and 10 emm1 isolates from throat swabs (2016-2018) underwent analysis. The presence of the scarlet fever-associated prophages and the specific single nucleotide polymorphisms of the M1UK clone were determined by polymerase chain reaction and the genome sequencing.

RESULTS

The M1UK lineage strains from throat swab and blood samples were identified. One of the M1UK strain in Taiwan carried the scarlet fever-associated prophage and therefore acquired the ssa, speC, and spd1 toxin repertoire. Nonetheless, the increase of M1UK was not observed until 2021, and there was a reduction in the diversity of emm types in 2020-2021, possibly due to the COVID-19 pandemic restriction policies in Taiwan.

CONCLUSIONS

Our results suggested that the M1UK lineage clone has introduced in Taiwan. In Taiwan, the COVID-19 restrictions were officially released in March 2023; therefore, it would be crucial to continuously monitor the M1UK expansion and its related diseases in the post COVID-19 era.

Antibiotics to eradicate Streptococcus pyogenes pharyngeal carriage in asymptomatic children and adults: A systematic review

Streptococcus pyogenes (S. pyogenes) is a Gram-positive bacteria which causes a spectrum of diseases ranging from asymptomatic infection to life-threatening sepsis. Studies report up to 2000 times greater risk of invasive S. pyogenes disease in close contacts of index cases within 30-days of symptom onset. Despite this, there is variability in the management of asymptomatic carriage of S. pyogenes and those at risk of secondary cases of invasive S. pyogenes infection.

OBJECTIVE

Our systematic review assessed the efficacy of different antibiotic regimens used for eradication of S. pyogenes from the pharynx in asymptomatic individuals.

METHODS

We searched Pubmed, EMBASE (1974-), OVID Medline (1948-) and the Cochrane CENTRAL registry. We included randomised controlled trials (RCTs) with asymptomatic participants with >50% with pharyngeal cultures positive with S. pyogenes at baseline. Only studies with microbiological methods including culture (+/- polymerase chain reaction, PCR) were included. We included studies published in English. Each included study was assessed by two independent reviewers for data extraction and risk of bias.

RESULTS

Of 1166 unique records identified, three RCTs were included in the review. Two of the three included RCTs found oral clindamycin for 10-days was the most efficacious regimen, compared to intramuscular benzathine penicillin G followed by 4 days of oral rifampicin, or monotherapy using benzathine penicillin, phenoxymethylpenicillin or erythromycin. Two RCTs were assessed as being at high risk of bias, with the third study demonstrating low/some risk of bias.

CONCLUSIONS

Current available evidence for the optimal antibiotic in eradicating pharyngeal S. pyogenes carriage is limited. Future RCTs should include penicillin, first-generation cephalosporins, rifampicin, macrolides (such as azithromycin) and clindamycin.

Insights gained from sequencing Australian non-invasive and invasive Streptococcus pyogenes isolates

Epidemiological data have indicated that invasive infections caused by the Gram-positive cocci Streptococcus pyogenes (group A streptococcus, GAS) have increased in many Australian states over the past two decades. In July 2022, invasive GAS (iGAS) infections became nationally notifiable in Australia via public-health agencies. Surveillance for S. pyogenes infections has been sporadic within the state of New South Wales (NSW). This has led to a lack of genetic data on GAS strains in circulation, particularly for non-invasive infections, which are the leading cause of GAS's burden on the Australian healthcare system. To address this gap, we used whole-genome sequencing to analyse the genomes of 318 S. pyogenes isolates collected within two geographical regions of NSW. Invasive isolates were collected in 2007-2017, whilst non-invasive isolates were collected in 2019-2021. We found that at least 66 different emm-types were associated with clinical disease within NSW. There was no evidence of any Australian-specific clones in circulation. The M1UK variant of the emm1 global pandemic clone (M1global) has been detected in our isolates from 2013 onwards. We detected antimicrobial-resistance genes (mainly tetM, ermA or ermB genes) in less than 10 % of our 318 isolates, which were more commonly associated with non-invasive infections. Superantigen virulence gene carriage was reasonably proportionate between non-invasive and invasive infection isolates. Our study adds rich data on the genetic makeup of historical S. pyogenes infections within Australia. Ongoing surveillance of invasive and non-invasive GAS infections within NSW by whole-genome sequencing is warranted to inform on outbreaks, antimicrobial resistance and vaccine coverage.

An assessment of the airborne longevity of group A Streptococcus

Group A streptococcus (GAS) infections result in more than 500 000 deaths annually. Despite mounting evidence for airborne transmission of GAS, little is known about its stability in aerosol. Measurements of GAS airborne stability were carried out using the Controlled Electrodynamic Levitation and Extraction of Bioaerosols onto a Substrate (CELEBS) instrument. CELEBS measurements with two different isolates of GAS suggest that it is aerostable, with approximately 70 % of bacteria remaining viable after 20 min of levitation at 50 % relative humidity (RH), with lower survival as RH was reduced. GAS airborne viability loss was driven primarily by desiccation and efflorescence (i.e. salt crystallization), with high pH also potentially playing a role, given reduced survival in bicarbonate containing droplet compositions. At low enough RH for efflorescence to occur, a greater proportion of organic components in the droplet appeared to protect the bacteria from efflorescence. These first insights into the aerosol stability of GAS indicate that airborne transmission of these respiratory tract bacteria may occur, and that both the composition of the droplet containing the bacteria, and the RH of the air affect the duration of bacterial survival in this environment. Future studies will explore a broader range of droplet and air compositions and include a larger selection of GAS strains.

Streptococcus pyogenes carriage acquisition, persistence and transmission dynamics within households in The Gambia (SpyCATS): protocol for a longitudinal household cohort study

Background

Streptococcus pyogenes (StrepA) causes a significant burden of disease globally from superficial infections to invasive disease. It is responsible for over 500,000 deaths each year, predominantly in low- and middle-income countries (LMIC). Superficial StrepA infections of the skin and pharynx can lead to rheumatic heart disease, the largest cause of StrepA-related deaths in LMIC. StrepA can also asymptomatically colonise normal skin and the pharynx (carriage), potentially increasing infection risk. Streptococcus dysgalactiae subsp. equisimilis (SDSE) carriage is also common in LMIC and may interact with StrepA. This study aims to investigate StrepA and SDSE carriage and infection epidemiology, transmission dynamics and naturally acquired immunity within households in The Gambia.

Methods

A longitudinal household observational cohort study will be conducted over one year. 45 households will be recruited from the urban area of Sukuta, The Gambia, resulting in approximately 450 participants. Households will be visited monthly, and available participants will undergo oropharyngeal and normal skin swabbing. Incident cases of pharyngitis and pyoderma will be captured via active case reporting, with swabs taken from disease sites. Swabs will be cultured for the presence of group A, C and G beta-haemolytic streptococci. Isolates will undergo whole genome sequencing. At each visit, clinical, socio-demographic and social mixing data will be collected. Blood serum will be collected at baseline and final visit. Oral fluid and dried blood spot samples will be collected at each visit. Mucosal and serum anti-StrepA antibody responses will be measured.

Outcome

This study will report StrepA and SDSE clinical epidemiology, risk factors, transmission dynamics, and serological responses to carriage and infection. Detailed social mixing behaviour will be combined with phylogenetic relatedness to model the extent of transmission occurring withing and between households. The study will provide data to help meet global strategic StrepA research goals.

Streptococcus pyogenes carriage acquisition, persistence and transmission dynamics within households in The Gambia (SpyCATS): protocol for a longitudinal household cohort study

BACKGROUND

Streptococcus pyogenes (StrepA) causes a significant burden of disease globally from superficial infections to invasive disease. It is responsible for over 500,000 deaths each year, predominantly in low- and middle-income countries (LMIC). Superficial StrepA infections of the skin and pharynx can lead to rheumatic heart disease, the largest cause of StrepA-related deaths in LMIC. StrepA can also asymptomatically colonise normal skin and the pharynx (carriage), potentially increasing infection risk. Streptococcus dysgalactiae subsp. equisimilis (SDSE) carriage is also common in LMIC and may interact with StrepA. This study aims to investigate StrepA and SDSE carriage and infection epidemiology, transmission dynamics and naturally acquired immunity within households in The Gambia.

METHODS

A longitudinal household observational cohort study will be conducted over one year. 45 households will be recruited from the urban area of Sukuta, The Gambia, resulting in approximately 450 participants. Households will be visited monthly, and available participants will undergo oropharyngeal and normal skin swabbing. Incident cases of pharyngitis and pyoderma will be captured via active case reporting, with swabs taken from disease sites. Swabs will be cultured for the presence of group A, C and G beta-haemolytic streptococci. Isolates will undergo whole genome sequencing. At each visit, clinical, socio-demographic and social mixing data will be collected. Blood serum will be collected at baseline and final visit. Oral fluid and dried blood spot samples will be collected at each visit. Mucosal and serum anti-StrepA antibody responses will be measured.

OUTCOME

This study will report StrepA and SDSE clinical epidemiology, risk factors, transmission dynamics, and serological responses to carriage and infection. Detailed social mixing behaviour will be combined with phylogenetic relatedness to model the extent of transmission occurring withing and between households. The study will provide data to help meet global strategic StrepA research goals.

Research priorities for the primordial prevention of acute rheumatic fever and rheumatic heart disease by modifying the social determinants of health

The social determinants of health (SDH), such as access to income, education, housing and healthcare, strongly shape the occurrence of acute rheumatic fever (ARF) and rheumatic heart disease (RHD) at the household, community and national levels. The SDH are systemic factors that privilege some more than others and result in poverty and inequitable access to resources to support health and well-being. Primordial prevention is the modification of SDH to improve health and reduce the risk of disease acquisition and the subsequent progression to RHD. Modifying these determinants using primordial prevention strategies can reduce the risk of exposure to Group A Streptococcus, a causative agent of throat and skin infections, thereby lowering the risk of initiating ARF and its subsequent progression to RHD.This report summarises the findings of the Primordial Prevention Working Group-SDH, which was convened in November 2021 by the National Heart, Lung, and Blood Institute to assess how SDH influence the risk of developing RHD. Working group members identified a series of knowledge gaps and proposed research priorities, while recognising that community engagement and partnerships with those with lived experience will be integral to the success of these activities. Specifically, members emphasised the need for: (1) global analysis of disease incidence, prevalence and SDH characteristics concurrently to inform policy and interventions, (2) global assessment of legacy primordial prevention programmes to help inform the co-design of interventions alongside affected communities, (3) research to develop, implement and evaluate scalable primordial prevention interventions in diverse settings and (4) research to improve access to and equity of services across the RHD continuum. Addressing SDH, through the implementation of primordial prevention strategies, could have broader implications, not only improving RHD-related health outcomes but also impacting other neglected diseases in low-resource settings.

Research opportunities for the primary prevention and management of acute rheumatic fever and rheumatic heart disease: a National Heart, Lung, and Blood Institute workshop report

Primary prevention of acute rheumatic fever (ARF) and rheumatic heart disease (RHD) encompasses the timely diagnosis and adequate treatment of the superficial group A Streptococcus (GAS) infections pharyngitis and impetigo. GAS is the only known inciting agent in the pathophysiology of the disease. However, sufficient evidence indicates that the uptake and delivery of primary prevention approaches in RHD-endemic regions are significantly suboptimal. This report presents expert deliberations on priority research and implementation opportunities for primary prevention of ARF/RHD that were developed as part of a workshop convened by the US National Heart, Lung, and Blood Institute in November 2021. The opportunities identified by the Primary Prevention Working Group encompass epidemiological, laboratory, clinical, implementation and dissemination research domains and are anchored on five pillars including: (A) to gain a better understanding of superficial GAS infection epidemiology to guide programmes and policies; (B) to improve diagnosis of superficial GAS infections in RHD endemic settings; (C) to develop scalable and sustainable models for delivery of primary prevention; (D) to understand potential downstream effects of the scale-up of primary prevention and (E) to develop and conduct economic evaluations of primary prevention strategies in RHD endemic settings. In view of the multisectoral stakeholders in primary prevention strategies, we emphasise the need for community co-design and government engagement, especially in the implementation and dissemination research arena. We present these opportunities as a reference point for research organisations and sponsors who aim to contribute to the increasing momentum towards the global control and prevention of RHD.

Searching for Strep A in the clinical environment during a human challenge trial: a sub-study protocol

Streptococcus pyogenes (also known as group A Streptococcus , Strep A) is an obligate human pathogen with significant global morbidity and mortality. Transmission is believed to occur primarily between individuals via respiratory droplets, but knowledge about other potential sources of transmission via aerosols or the environment is limited. Such knowledge is required to design optimal interventions to control transmission, particularly in endemic settings. We aim to detail an experimental methodology to assess the transmission potential of Strep A in a clinical environment. We will examine potential sources of transmission in up to 20 participants recruited to the Controlled human infection for penicillin against Streptococcus pyogenes (CHIPS) Trial. Three approaches to understanding transmission will be used: the use of selective agar settle plates to capture possible droplet or airborne spread of Strep A; measurement of the possible distance of Strep A droplet spread during conversation; and environmental swabbing of personal and common high-touch items to detect the presence of Strep A on hard and soft surfaces. All methods are designed to allow for an assessment of transmission potential by symptomatic, asymptomatic and non-cases. Ethical approval has been obtained through Bellberry Human Research Ethics Committee (approval 2021-03-295). Trial registration number: ACTRN12621000751875. Any results elicited from these experiments will be of benefit to the scientific literature in improving our knowledge of opportunities to prevent Strep A transmission as a direct component of the primordial prevention of rheumatic fever. Findings will be reported at local, national and international conferences and in peer-reviewed journals.

Evaluating the role of asymptomatic throat carriage of Streptococcus pyogenes in impetigo transmission in remote Aboriginal communities in Northern Territory, Australia: a retrospective genomic analysis

BACKGROUND

Streptococcus pyogenes, or group A Streptococcus (GAS), infections contribute to a high burden of disease in Aboriginal Australians, causing skin infections and immune sequelae such as rheumatic heart disease. Controlling skin infections in these populations has proven difficult, with transmission dynamics being poorly understood. We aimed to identify the relative contributions of impetigo and asymptomatic throat carriage to GAS transmission.

METHODS

In this genomic analysis, we retrospectively applied whole genome sequencing to GAS isolates that were collected as part of an impetigo surveillance longitudinal household survey conducted in three remote Aboriginal communities in the Northern Territory of Australia between Aug 6, 2003, and June 22, 2005. We included GAS isolates from all throats and impetigo lesions of people living in two of the previously studied communities. We classified isolates into genomic lineages based on pairwise shared core genomes of more than 99% with five or fewer single nucleotide polymorphisms. We used a household network analysis of epidemiologically and genomically linked lineages to quantify the transmission of GAS within and between households.

FINDINGS

We included 320 GAS isolates in our analysis: 203 (63%) from asymptomatic throat swabs and 117 (37%) from impetigo lesions. Among 64 genomic lineages (encompassing 39 emm types) we identified 264 transmission links (involving 93% of isolates), for which the probable source was asymptomatic throat carriage in 166 (63%) and impetigo lesions in 98 (37%). Links originating from impetigo cases were more frequent between households than within households. Households were infected with GAS for a mean of 57 days (SD 39 days), and once cleared, reinfected 62 days (SD 40 days) later. Increased household size and community presence of GAS and scabies were associated with slower clearance of GAS.

INTERPRETATION

In communities with high prevalence of endemic GAS-associated skin infection, asymptomatic throat carriage is a GAS reservoir. Public health interventions such as vaccination or community infection control programmes aimed at interrupting transmission of GAS might need to include consideration of asymptomatic throat carriage.

FUNDING

Australian National Health and Medical Research Council.

Pathogenesis, epidemiology and control of Group A Streptococcus infection

Streptococcus pyogenes (Group A Streptococcus; GAS) is exquisitely adapted to the human host, resulting in asymptomatic infection, pharyngitis, pyoderma, scarlet fever or invasive diseases, with potential for triggering post-infection immune sequelae. GAS deploys a range of virulence determinants to allow colonization, dissemination within the host and transmission, disrupting both innate and adaptive immune responses to infection. Fluctuating global GAS epidemiology is characterized by the emergence of new GAS clones, often associated with the acquisition of new virulence or antimicrobial determinants that are better adapted to the infection niche or averting host immunity. The recent identification of clinical GAS isolates with reduced penicillin sensitivity and increasing macrolide resistance threatens both frontline and penicillin-adjunctive antibiotic treatment. The World Health Organization (WHO) has developed a GAS research and technology road map and has outlined preferred vaccine characteristics, stimulating renewed interest in the development of safe and effective GAS vaccines.

[Paying attention to the epidemic of group A Streptococcus infections in multiple European and American countries]

At the end of 2022, the World Health Organization reported an increase in group A Streptococcus (GAS) infections, such as scarlet fever, in multiple countries. The outbreak primarily affected children under 10 years old, and the number of deaths was higher than anticipated, causing international concern. This paper reviews the current state of the GAS disease outbreak, its causes, and response measures. The authors aim to draw attention from clinical workers in China and increase their awareness and vigilance regarding this epidemic. Healthcare workers should be aware of the potential epidemiological changes in infectious diseases that may arise after the optimization of control measures for coronavirus disease 2019 to ensure children's health.

Changes in the Incidence of Invasive Bacterial Disease During the COVID-19 Pandemic in the United States, 2014-2020

BACKGROUND

Descriptions of changes in invasive bacterial disease (IBD) epidemiology during the coronavirus disease 2019 (COVID-19) pandemic in the United States are limited.

METHODS

We investigated changes in the incidence of IBD due to Streptococcus pneumoniae, Haemophilus influenzae, group A Streptococcus (GAS), and group B Streptococcus (GBS). We defined the COVID-19 pandemic period as 1 March to 31 December 2020. We compared observed IBD incidences during the pandemic to expected incidences, consistent with January 2014 to February 2020 trends. We conducted secondary analysis of a health care database to assess changes in testing by blood and cerebrospinal fluid (CSF) culture during the pandemic.

RESULTS

Compared with expected incidences, the observed incidences of IBD due to S. pneumoniae, H. influenzae, GAS, and GBS were 58%, 60%, 28%, and 12% lower during the pandemic period of 2020, respectively. Declines from expected incidences corresponded closely with implementation of COVID-19-associated nonpharmaceutical interventions (NPIs). Significant declines were observed across all age and race groups, and surveillance sites for S. pneumoniae and H. influenzae. Blood and CSF culture testing rates during the pandemic were comparable to previous years.

CONCLUSIONS

NPIs likely contributed to the decline in IBD incidence in the United States in 2020; observed declines were unlikely to be driven by reductions in testing.

Group A Streptococcus Is Still at Large

Group A Streptococcus (GAS) is a major human pathogen that can cause diseases, ranging from mild to severe systemic and invasive diseases [...].

Characterization of emergent toxigenic M1UK Streptococcus pyogenes and associated sublineages

Streptococcus pyogenes genotype emm1 is a successful, globally distributed epidemic clone that is regarded as inherently virulent. An emm1 sublineage, M1UK, that produces increased levels of SpeA toxin was associated with increased scarlet fever and invasive infections in England in 2015/2016. Defined by 27 SNPs in the core genome, M1UK is now dominant in England. To more fully characterize M1UK, we undertook comparative transcriptomic and proteomic analyses of M1UK and contemporary non-M1UK emm1 strains (M1global). Just seven genes were differentially expressed by M1UK compared with contemporary M1global strains. In addition to speA, five genes in the operon that includes glycerol dehydrogenase were upregulated in M1UK (gldA, mipB/talC, pflD, and phosphotransferase system IIC and IIB components), while aquaporin (glpF2) was downregulated. M1UK strains have a stop codon in gldA. Deletion of gldA in M1global abrogated glycerol dehydrogenase activity, and recapitulated upregulation of gene expression within the operon that includes gldA, consistent with a feedback effect. Phylogenetic analysis identified two intermediate emm1 sublineages in England comprising 13/27 (M113SNPs) and 23/27 SNPs (M123SNPs), respectively, that had failed to expand in the population. Proteomic analysis of invasive strains from the four phylogenetic emm1 groups highlighted sublineage-specific changes in carbohydrate metabolism, protein synthesis and protein processing; upregulation of SpeA was not observed in chemically defined medium. In rich broth, however, expression of SpeA was upregulated ~10-fold in both M123SNPs and M1UK sublineages, compared with M113SNPs and M1global. We conclude that stepwise accumulation of SNPs led to the emergence of M1UK. While increased expression of SpeA is a key indicator of M1UK and undoubtedly important, M1UK strains have outcompeted M123SNPs and other emm types that produce similar or more superantigen toxin. We speculate that an accumulation of adaptive SNPs has contributed to a wider fitness advantage in M1UK on an inherently successful emm1 streptococcal background.

Detection of Streptococcus pyogenes M1UK in Australia and characterization of the mutation driving enhanced expression of superantigen SpeA

A new variant of Streptococcus pyogenes serotype M1 (designated 'M1_UK') has been reported in the United Kingdom, linked with seasonal scarlet fever surges, marked increase in invasive infections, and exhibiting enhanced expression of the superantigen SpeA. The progenitor S. pyogenes 'M1_global' and M1_UK clones can be differentiated by 27 SNPs and 4 indels, yet the mechanism for speA upregulation is unknown. Here we investigate the previously unappreciated expansion of M1_UK in Australia, now isolated from the majority of serious infections caused by serotype M1 S. pyogenes. M1_UK sub-lineages circulating in Australia also contain a novel toxin repertoire associated with epidemic scarlet fever causing S. pyogenes in Asia. A single SNP in the 5' transcriptional leader sequence of the transfer-messenger RNA gene ssrA drives enhanced SpeA superantigen expression as a result of ssrA terminator read-through in the M1_UK lineage. This represents a previously unappreciated mechanism of toxin expression and urges enhanced international surveillance.

Correlates of immunity to Group A Streptococcus: a pathway to vaccine development

Understanding immunity in humans to Group A Streptococcus (Strep A) is critical for the development of successful vaccines to prevent the morbidity and mortality attributed to Strep A infections. Despite decades of effort, no licensed vaccine against Strep A exists and immune correlates of protection are lacking; a major impediment to vaccine development. In the absence of a vaccine, we can take cues from the development of natural immunity to Strep A in humans to identify immune correlates of protection. The age stratification of incidence of acute Strep A infections, peaking in young children and waning in early adulthood, coincides with the development of specific immune responses. Therefore, understanding the immune mechanisms involved in natural protection from acute Strep A infection is critical to identifying immune correlates to inform vaccine development. This perspective summarises the findings from natural infection studies, existing assays of immunity to Strep A, and highlights the gaps in knowledge to guide the development of Strep A vaccines and associated correlates of protection.

Transmission of SARS-CoV-2 by children to contacts in schools and households: a prospective cohort and environmental sampling study in London

BACKGROUND

Assessing transmission of SARS-CoV-2 by children in schools is of crucial importance to inform public health action. We assessed frequency of acquisition of SARS-CoV-2 by contacts of pupils with COVID-19 in schools and households, and quantified SARS-CoV-2 shedding into air and onto fomites in both settings.

METHODS

We did a prospective cohort and environmental sampling study in London, UK in eight schools. Schools reporting new cases of SARS-CoV-2 infection to local health protection teams were invited to take part if a child index case had been attending school in the 48 h before a positive SARS-CoV-2 PCR test. At the time of the study, PCR testing was available to symptomatic individuals only. Children aged 2-14 years (extended to <18 years in November, 2020) with a new nose or throat swab SARS-CoV-2 positive PCR from an accredited laboratory were included. Incidents involving exposure to at least one index pupil with COVID-19 were identified (the prevailing variants were original, α, and δ). Weekly PCR testing for SARS-CoV-2 was done on immediate classroom contacts (the so-called bubble), non-bubble school contacts, and household contacts of index pupils. Testing was supported by genome sequencing and on-surface and air samples from school and home environments.

FINDINGS

Between October, 2020, and July, 2021 from the eight schools included, secondary transmission of SARS-CoV-2 was not detected in 28 bubble contacts, representing ten bubble classes (participation rate 8·8% [IQR 4·6-15·3]). Across eight non-bubble classes, 3 (2%) of 62 pupils tested positive, but these were unrelated to the original index case (participation rate 22·5% [9·7-32·3]). All three were asymptomatic and tested positive in one setting on the same day. In contrast, secondary transmission to previously negative household contacts from infected index pupils was found in six (17%) of 35 household contacts rising to 13 (28%) of 47 household contacts when considering all potential infections in household contacts. Environmental contamination with SARS-CoV-2 was rare in schools: fomite SARS-CoV-2 was identified in four (2%) of 189 samples in bubble classrooms, two (2%) of 127 samples in non-bubble classrooms, and five (4%) of 130 samples in washrooms. This contrasted with fomites in households, where SARS-CoV-2 was identified in 60 (24%) of 248 bedroom samples, 66 (27%) of 241 communal room samples, and 21 (11%) 188 bathroom samples. Air sampling identified SARS-CoV-2 RNA in just one (2%) of 68 of school air samples, compared with 21 (25%) of 85 air samples taken in homes.

INTERPRETATION

There was no evidence of large-scale SARS-CoV-2 transmission in schools with precautions in place. Low levels of environmental contamination in schools are consistent with low transmission frequency and suggest adequate cleaning and ventilation in schools during the period of study. The high frequency of secondary transmission in households associated with evident viral shedding throughout the home suggests a need to improve advice to households with infection in children to prevent onward community spread. The data suggest that SARS-CoV-2 transmission from children in any setting is very likely to occur when precautions are reduced.

FUNDING

UK Research and Innovation and UK Department of Health and Social Care, National Institute for Health and Care Research.

The effects of sugar in drinking water on Streptococcus pyogenes colonisation in a murine nasopharyngeal infection model

The number of sugar-sweetened beverages consumed per day has been associated with an increased risk of acute rheumatic fever, an autoimmune disease triggered by superficial Streptococcus pyogenes infection. To explore if there could be a biological basis for this association, we used a mouse model of S. pyogenes nasopharyngeal colonisation combined with a dietary intervention. We observed an increased bacterial load in the nasopharynx of mice receiving sucrose drinking water post-infection, suggesting that high sucrose intake promotes S. pyogenes growth and/or survival. This provides new insight into the potential biological basis behind the association seen in humans.

Decreased Antibiotic Consumption Coincided with Reduction in Bacteremia Caused by Bacterial Species with Respiratory Transmission Potential during the COVID-19 Pandemic

Nonpharmaceutical interventions implemented during the COVID-19 pandemic (2020−2021) have provided a unique opportunity to understand their impact on the wholesale supply of antibiotics and incidences of infections represented by bacteremia due to common bacterial species in Hong Kong. The wholesale antibiotic supply data (surrogate indicator of antibiotic consumption) and notifications of scarlet fever, chickenpox, and tuberculosis collected by the Centre for Health Protection, and the data of blood cultures of patients admitted to public hospitals in Hong Kong collected by the Hospital Authority for the last 10 years, were tabulated and analyzed. A reduction in the wholesale supply of antibiotics was observed. This decrease coincided with a significant reduction in the incidence of community-onset bacteremia due to Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, which are encapsulated bacteria with respiratory transmission potential. This reduction was sustained during two pandemic years (period 2: 2020−2021), compared with eight pre-pandemic years (period 1: 2012−2019). Although the mean number of patient admissions per year (1,704,079 vs. 1,702,484, p = 0.985) and blood culture requests per 1000 patient admissions (149.0 vs. 158.3, p = 0.132) were not significantly different between periods 1 and 2, a significant reduction in community-onset bacteremia due to encapsulated bacteria was observed in terms of the mean number of episodes per year (257 vs. 58, p < 0.001), episodes per 100,000 admissions (15.1 vs. 3.4, p < 0.001), and per 10,000 blood culture requests (10.1 vs. 2.1, p < 0.001), out of 17,037,598 episodes of patient admissions with 2,570,164 blood culture requests. Consistent with the findings of bacteremia, a reduction in case notification of scarlet fever and airborne infections, including tuberculosis and chickenpox, was also observed; however, there was no reduction in the incidence of hospital-onset bacteremia due to Staphylococcus aureus or Escherichia coli. Sustained implementation of non-pharmaceutical interventions against respiratory microbes may reduce the overall consumption of antibiotics, which may have a consequential impact on antimicrobial resistance. Rebound of conventional respiratory microbial infections is likely with the relaxation of these interventions.