The Shr receptor from Streptococcus pyogenes uses a cap and release mechanism to acquire heme-iron from human hemoglobin.

Streptococcus pyogenes (group A Streptococcus) is a clinically important microbial pathogen that requires iron in order to proliferate. During infections, S. pyogenes uses the surface displayed Shr receptor to capture human hemoglobin (Hb) and acquires its iron-laden heme molecules. Through a poorly understood mechanism, Shr engages Hb via two structurally unique N-terminal Hb-interacting domains (HID1 and HID2) which facilitate heme transfer to proximal NEAr Transporter (NEAT) domains. Based on the results of X-ray crystallography, small angle X-ray scattering, NMR spectroscopy, native mass spectrometry, and heme transfer experiments, we propose that Shr utilizes a "cap and release" mechanism to gather heme from Hb. In the mechanism, Shr uses the HID1 and HID2 modules to preferentially recognize only heme-loaded forms of Hb by contacting the edges of its protoporphyrin rings. Heme transfer is enabled by significant receptor dynamics within the Shr-Hb complex which function to transiently uncap HID1 from the heme bound to Hb's ß subunit, enabling the gated release of its relatively weakly bound heme molecule and subsequent capture by Shr's NEAT domains. These dynamics may maximize the efficiency of heme scavenging by S. pyogenes, enabling it to preferentially recognize and remove heme from only heme-loaded forms of Hb that contain iron.

Molecular characterization of the interaction between human IgG and the M-related proteins from Streptococcus pyogenes.

Group A Streptococcal M-related proteins (Mrps) are dimeric α-helical-coiled-coil cell membrane-bound surface proteins. During infection, Mrp recruit the fragment crystallizable region of human immunoglobulin G via their A-repeat regions to the bacterial surface, conferring upon the bacteria enhanced phagocytosis resistance and augmented growth in human blood. However, Mrps show a high degree of sequence diversity, and it is currently not known whether this diversity affects the Mrp-IgG interaction. Herein, we report that diverse Mrps all bind human IgG subclasses with nanomolar affinity, with differences in affinity which ranged from 3.7 to 11.1 nM for mixed IgG. Using surface plasmon resonance, we confirmed Mrps display preferential IgG-subclass binding. All Mrps were found to have a significantly weaker affinity for IgG3 (p < 0.05) compared to all other IgG subclasses. Furthermore, plasma pulldown assays analyzed via Western blotting revealed that all Mrp were able to bind IgG in the presence of other serum proteins at both 25 °C and 37 °C. Finally, we report that dimeric Mrps bind to IgG with a 1:1 stoichiometry, enhancing our understanding of this important host-pathogen interaction.

Large Clusters of Invasive emm49 Group A Streptococcus Identified Within Arizona Health Care Facilities Through Statewide Genomic Surveillance System, 2019-2021.

A statewide genomic surveillance system for invasive Group A Streptococcus was implemented in Arizona in June 2019, resulting in 1046 isolates being submitted for genomic analysis to characterize emm types and identify transmission clusters. Eleven of the 32 identified distinct emm types comprised >80% of samples, with 29.7% of all isolates being typed as emm49 (and its genetic derivative emm151). Phylogenetic analysis initially identified an emm49 genomic cluster of 4 isolates that rapidly expanded over subsequent months (June 2019 to February 2020). Public health investigations identified epidemiologic links with 3 different long-term care facilities, resulting in specific interventions. Unbiased genomic surveillance allowed for identification and response to clusters that would have otherwise remained undetected.

Serological responses to target Streptococcus pyogenes vaccine antigens in patients with proven invasive beta-haemolytic streptococcal infections.

BACKGROUND: Rising incidence of invasive beta-haemolytic streptococcal (iBHS) infections has prompted consideration of vaccination as a preventative strategy for at-risk populations. The benefits of a vaccine targeting Lancefield group A (Streptococcus pyogenes; Strep A) would increase if cross-species immunity against Lancefield groups C/G (Streptococcus dysgalactiae subspecies equisimilis; SDSE) and B (Streptococcus agalactiae; GBS) was demonstrated. METHODS: A prospective, observational study of adult patients with iBHS infections due to Strep A, SDSE or GBS. Antibody responses to six Strep A candidate antigens were assayed on acute and convalescent sera. A serological response was defined as an increase of >0.2log10 arbitrary units/mL (AU/mL). RESULTS: Sixty-seven participants were enrolled. Thirty-three participants were included in the final analysis (12, 11 and 10 with Strep A, SDSE and GBS, respectively). The median serological response for participants with Strep A was significant for all tested antigens (median >0.2log10 difference between acute and convalescent samples; P<0.05 for all). Those with SDSE had comparable and significant median (IQR) responses to streptolysin-O (0.65 [0.36-1.67], P=0.004), S. pyogenes adhesion and division protein (0.68 [0.36-1.63], P=0.005) and C5a peptidase (ScpA; 0.30 [0.23-1.06]), P=0.004). GBS responses were limited to ScpA only (0.34 [0.08-0.52], P=0.05). CONCLUSION: Patients with invasive Strep A infection mount robust antibody responses to six non-M protein vaccine candidate antigens. Similar significant responses to C5a peptidase in those with invasive SDSE and GBS infection highlight the importance of further research into cross-species protection and immunological correlates of vaccine efficacy.

Group A Streptococcus induces lysosomal dysfunction in THP-1 macrophages.

The human-specific bacterial pathogen group A Streptococcus (GAS) is a significant cause of morbidity and mortality. Macrophages are important to control GAS infection, but previous data indicate that GAS can persist in macrophages. In this study, we detail the molecular mechanisms by which GAS survives in THP-1 macrophages. Our fluorescence microscopy studies demonstrate that GAS is readily phagocytosed by macrophages, but persists within phagolysosomes. These phagolysosomes are not acidified, which is in agreement with our findings that GAS cannot survive in low pH environments. We find that the secreted pore-forming toxin Streptolysin O (SLO) perforates the phagolysosomal membrane, allowing leakage of not only protons but also large proteins including the lysosomal protease cathepsin B. Additionally, GAS recruits CD63/LAMP-3, which may contribute to lysosomal permeabilization, especially in the absence of SLO. Thus, although GAS does not inhibit fusion of the lysosome with the phagosome, it has multiple mechanisms to prevent proper phagolysosome function, allowing for persistence of the bacteria within the macrophage. This has important implications for not only the initial response but also the overall functionality of the macrophages, which may lead to the resulting pathologies in GAS infection. Our data suggest that therapies aimed at improving macrophage function may positively impact patient outcomes in GAS infection.

The Streptococcus pyogenes stand-alone regulator RofA exhibits characteristics of a PRD-containing virulence regulator.

Streptococcus pyogenes [group A streptococcus (GAS)] is a human pathogen capable of infecting diverse tissues. To successfully infect these sites, GAS must detect available nutrients and adapt accordingly. The phosphoenolpyruvate transferase system (PTS) mediates carbohydrate uptake and metabolic gene regulation to adapt to the nutritional environment. Regulation by the PTS can occur through phosphorylation of transcriptional regulators at conserved PTS-regulatory domains (PRDs). GAS has several PRD-containing stand-alone regulators with regulons encoding both metabolic genes and virulence factors [PRD-containing virulence regulators (PCVRs)]. One is RofA, which regulates the expression of virulence genes in multiple GAS serotypes. It was hypothesized that RofA is phosphorylated by the PTS in response to carbohydrate levels to coordinate virulence gene expression. In this study, the RofA regulon of M1T1 strain 5448 was determined using RNA sequencing. Two operons were consistently differentially expressed across growth in the absence of RofA; the pilus operon was downregulated, and the capsule operon was upregulated. This correlated with increased capsule production and decreased adherence to keratinocytes. Purified RofA-His was phosphorylated in vitro by PTS proteins EI and HPr, and phosphorylated RofA-FLAG was detected in vivo when GAS was grown in low-glucose C medium. Phosphorylated RofA was not observed when C medium was supplemented 10-fold with glucose. Mutations of select histidine residues within the putative PRDs contributed to the in vivo phosphorylation of RofA, although phosphorylation of RofA was still observed, suggesting other phosphorylation sites exist in the protein. Together, these findings support the hypothesis that RofA is a PCVR that may couple sugar metabolism with virulence regulation.

Spatiotemporal Trends in Group A Streptococcal Pharyngitis in the United States.

BACKGROUND: Group A Streptococcus (GAS) causes an estimated 5.2 million outpatient visits for pharyngitis annually in the United States, with incidence peaking in winter, but the annual spatiotemporal pattern of GAS pharyngitis across the United States is poorly characterized. METHODS: We used outpatient claims data from individuals with private medical insurance between 2010 and 2018 to quantify GAS pharyngitis visit rates across U.S. census regions, subregions, and states. We evaluated seasonal and age-based patterns of geographic spread and the association between school start dates and the summertime upward inflection in GAS visits. RESULTS: The South had the most visits per person (yearly average, 39.11 visits per 1000 people; 95% confidence interval, 36.21-42.01) and the West had the fewest (yearly average, 17.63 visits per 1000 people; 95% confidence interval, 16.76-18.49). Visits increased earliest in the South and in school-age children. Differences in visits between the South and other regions were most pronounced in the late summer through early winter. Visits peaked earliest in central southern states, in December to January, and latest on the coasts, in March. The onset of the rise in GAS pharyngitis visits correlated with, but preceded, average school start times. CONCLUSIONS: The burden and timing of GAS pharyngitis varied across the continental United States, with the South experiencing the highest overall rates and earliest onset and peak in outpatient visits. Understanding the drivers of these regional differences in GAS pharyngitis will help in identifying and targeting prevention measures.

Invasive Group A Streptococcus Hypervirulent M1UK Clone, Canada, 2018-2023.

To determine invasive group A Streptococcus trends in Canada, we characterized emm1 isolates collected during 2018-2023. The percentage of hypervirulent M1UK lineage isolates increased significantly, from 22.1% in 2018 to 60.2% in 2023. Genomic analysis identified geographically and temporally associated clusters and genes associated with virulent bacteriophage acquisition.

Computerized Decision Support Systems Informing Community-Acquired Pneumonia Surveillance, France, 2017-2023.

We show the value of real-time data generated by a computerized decision support system in primary care in strengthening pneumonia surveillance. The system showed a 66% (95% CI 64%-67%) increase in community-acquired pneumonia from 2018 to 2023 for the population of France, 1 month before a national alert was issued.

Epidemiology of Streptococcus pyogenes Disease before, during, and after COVID-19 Pandemic, Germany, 2005-2023.

We analyzed 3,081 invasive and noninvasive Streptococcus pyogenes cases (January 2005-December 2023) at a tertiary care hospital in southwest Germany. Absolute numbers of case-patients increased each year from 2005 until the COVID-19 pandemic. Odds ratios for invasive streptococcal disease were significantly influenced by year, male sex, and older age.

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.

Different Group A Streptococcus pili lead to varying proinflammatory cytokine responses and virulence.

The human pathogen Streptococcus pyogenes, or Group A Streptococcus (GAS), is associated with a variety of diseases ranging from mild skin and soft tissue infections to invasive diseases and immune sequelae such as rheumatic heart disease. We have recently reported that one of the virulence factors of this pathogen, the pilus, has inflammatory properties and strongly stimulates the innate immune system. Here we used a range of nonpathogenic Lactococcus lactis gain-of-function mutants, each expressing one of the major pilus types of GAS, to compare the immune responses generated by various types of fully assembled pili. In vitro assays indicated variability in the inflammatory response induced by different pili, with the fibronectin-binding, collagen-binding, T antigen (FCT)-1-type pilus from GAS serotype M6/T6 inducing significantly stronger cytokine secretion than other pili. Furthermore, we established that the same trend of pili-mediated immune response could be modeled in Galleria mellonella larvae, which possess a similar innate immune system to vertebrates. Counterintuitively, across the panel of pili types examined in this study, we observed a negative correlation between the intensity of the immune response demonstrated in our experiments and the disease severity observed clinically in the GAS strains associated with each pilus type. This observation suggests that pili-mediated inflammation is more likely to promote bacterial clearance instead of causing disruptive damages that intensify pathogenesis. This also indicates that pili may not be the main contributor to the inflammatory symptoms seen in GAS diseases. Rather, the immune-potentiating properties of the pilus components could potentially be exploited as a vaccine adjuvant.

Divergent effects of emm types 1 and 12 on invasive group A streptococcal infections-results of a retrospective cohort study, Germany 2023.

As a potential side effect of the severe acute respiratory syndrome coronavirus type 2 pandemic, invasive group A Streptococcus (iGAS) infections in Europe have increased dramatically in both children and adults in the end of 2022. This epidemiological and molecular study describes the distributions of streptococcal genes encoding the M antigen (emm types) and superantigens in patients with invasive and non-invasive GAS infections. From December 2022 to December 2023, a total of 163 GAS isolates were collected from sterile and non-sterile sites of patients at five hospitals in Germany including two tertiary care centers. Genes encoding M protein and superantigens were determined following the guidelines of CDC Streptococcus laboratory. Patients' characteristics were reviewed retrospectively. Correlations of clinical factors, emm types, and superantigens with rates of invasive infections were analyzed. Of the 163 included GAS cases, 112 (69%) were considered as invasive. In total, 33 different emm types were observed, of which emm1.0 (n = 49; 30%), emm89.0 (n = 15; 9%), and emm12.0 (n = 14; 9%) were most prevalent. In total, 70% of emm1.0 isolates belonged to M1UK lineage. No difference in invasive infections was observed for the M1UK lineage compared with other emm1.0 isolates. However, the emm1.0 type, presence of speA1-3, speG, or speJ, as well as adulthood were significantly associated with invasive infections. In contrast, emm12.0 isolates were significantly less associated with invasive infections. Multivariable analysis confirmed a significant influence of speJ and adulthood on iGAS infections. This study underlines the importance of continuous monitoring of genomic trends and identification of emerging GAS variants. This may aid in delineating pathogenicity factors of Streptococcus pyogenes that propel invasive infections.

Nationwide upsurge in invasive disease in the context of longitudinal surveillance of carriage and invasive Streptococcus pyogenes 2009-2023, the Netherlands: a molecular epidemiological study.

Since 2022, many countries have reported an upsurge in invasive group A streptococcal (iGAS) infections. We explored whether changes in Streptococcus pyogenes carriage rates or emergence of strains with potentially altered virulence, such as emm1 variants M1UK and M1DK, contributed to the 2022/2023 surge in the Netherlands. We determined emm (sub)type distribution for 2,698 invasive and 351 S. pyogenes carriage isolates collected between January 2009 and March 2023. Genetic evolution of emm1 was analyzed by whole-genome sequencing of 497 emm1 isolates. The nationwide iGAS upsurge coincided with a sharp increase of emm1.0 from 18% (18/100) of invasive isolates in Q1 2022 to 58% (388/670) in Q1 2023 (Fisher's exact test, P < 0.0001). M1UK became dominant among invasive emm1 isolates in 2016 and further expanded from 72% in Q1 2022 to 96% in Q1 2023. Phylogenetic comparison revealed evolution and clonal expansion of four new M1UK clades in 2022/2023. DNase Spd1 and superantigen SpeC were acquired in 9% (46/497) of emm1 isolates. S. pyogenes carriage rates and emm1 proportions in carriage isolates remained stable during this surge, and the expansion of M1UK in iGAS was not reflected in carriage isolates. During the 2022/2023 iGAS surge in the Netherlands, expansion of four new M1UK clades was observed among invasive isolates, but not carriage isolates, suggesting increased virulence and fitness of M1UK compared to contemporary M1 strains. The emergence of more virulent clades has important implications for public health strategies such as antibiotic prophylaxis for close contacts of iGAS patients.IMPORTANCEThis study describes the molecular epidemiology of invasive group A streptococcal (iGAS) infections in the Netherlands based on >3,000 Streptococcus pyogenes isolates from both asymptomatic carriers and iGAS patients collected before, during, and after the COVID-19 pandemic period (2009-2023) and is the first to assess whether changes in carriage rates or carried emm types contributed to the alarming post-COVID-19 upsurge in iGAS infections. We show that the 2022/2023 iGAS surge coincided with a sharp increase of emm1, particularly the toxicogenic M1UK variant, in invasive isolates, but not in carriage isolates. These findings suggest that increased virulence and fitness of M1UK likely contributes to an increased dissemination between hosts. The emergence of a more virulent and fit lineage has important implications for iGAS control interventions such as antibiotic prophylaxis for close contacts of iGAS patients and calls for a reappraisal of iGAS control interventions and guidelines.

Treatment outcomes and their predictors in children hospitalized with varicella complicated by bacterial superinfections after pandemic of COVID-19 - a retrospective multicenter analysis of real-life data in Poland.

PURPOSE: The aim of this study was to analyze treatment outcomes and their predictors in children hospitalized due to varicella complicated by bacterial superinfections after pandemic of COVID-19. METHODS: This retrospective study analyzed data collected in a multicenter, nationwide, observational database dedicated for children aged 0-17 years hospitalized due to bacterial complications of varicella in 9 Polish tertiary healthcare inpatient centers. The primary endpoint of this study was the treatment outcome established after the end of hospital management assessed at a 4-point scale. The secondary endpoint was defined as the necessity of surgical intervention. RESULTS: There were 458 patients with a median age of 4 (IQR 2-6) years. After the completed treatment, 319 (69%) participants were found fully recovered; 132 (29%) had transient complications; 2 (0.5%) had persistent complications; and 1 child (0.5%) died. Multivariate analysis revealed that implementation of ibuprofen in pre-treatment management of a child with varicella was associated with a 4.07-fold (2.50-6.60) increase in risk of complications after the treatment and it was associated with 2.87 times (1.39-5.89) higher risk of surgical intervention necessity. For other pre-hospital interventions (implementation of acyclovir, antibiotics or antihistaminics) no significant impact was observed. GAS infection increased the necessity of surgical intervention by 7.51 (3.64-15.49) times. CONCLUSIONS: One-third of patients treated for bacterial complications of varicella have post-treatment complications, most of them transient. GAS infection increases the need for surgical intervention. The use of ibuprofen in the treatment of varicella significantly increases the risk of complications and the need for surgical intervention.

Epidemiology and emm types among group A streptococcal pharyngitis in Finland: a prospective laboratory-based study.

PURPOSE: Streptococcus pyogenes (mostly termed group A Streptococcus - GAS) is the most important bacterial causative of pharyngitis. However, epidemiology of GAS pharyngitis is not widely established. This study describes GAS pharyngitis cases and emm-type distribution in a prospective study covering over 2 years in two Hospital Districts in Finland. METHODS: A prospective, systematic collection of GAS pharyngitis isolates was conducted between March 2018 and December 2020 in two large Hospital Districts in Finland. Patient characteristics (age, gender) were included if available. All GAS isolates collected were emm typed. RESULTS: Altogether 1320 GAS pharyngitis strains were collected, 904 in the Hospital District 1 (HD1) and 416 in Hospital District 2 (HD2). In HD1, age and gender data were available. Females were overrepresented (58% of all cases). In addition, the age and gender distributions were noted to be significantly different (p < 0.0001) with females having a more uniform distribution until age of 40. emm28 was common among the age group of 20-29-year-olds and emm89 in children under 10 years of age, respectively. In HD1, most of the isolates were collected during winter and autumn months. Significant differences by season in the frequency of emm12, emm89, emm75 and group of "others" were observed. CONCLUSION: Age distribution among GAS pharyngitis cases was significantly different between genders (p < 0.0001). In addition, age group specific and seasonal variations in emm GAS types causing the disease were observed. These findings warrant further investigation, especially for understanding population-based spread of GAS even in more detail.

Group A Streptococcal meningitis in children: a short case series and systematic review.

BACKGROUND: Group A streptococcal(GAS) meningitis is a severe disease with a high case fatality rate. In the era of increasing GAS meningitis, our understanding about this disease is limited. PURPOSE: To gain a better understanding about GAS meningitis. METHODS: Five new cases with GAS meningitis were reported. GAS meningitis related literatures were searched for systematic review in PUBMED and EMBASE. Case reports and case series on paediatric cases were included. Information on demographics, risk factors, symptoms, treatments, outcomes, and emm types of GAS was summarized. RESULTS: Totally 263 cases were included. Among 100 individuals, 9.9% (8/81) had prior varicella, 11.1% (9/81) had anatomical factors, and 53.2% (42/79) had extracranial infections. Soft tissue infections were common among infants (10/29, 34.5%), while ear/sinus infections were more prevalent in children ≥ 3 years (21/42, 50.0%). The overall case fatality rate (CFR) was 16.2% (12/74). High risk of death was found in patients with shock or systemic complications, young children(< 3 years) and cases related to hematogenic spread. The predominate cause of death was shock(6/8). Among the 163 patients included in case series studies, ear/sinus infections ranged from 21.4 to 62.5%, while STSS/shock ranged from 12.5 to 35.7%, and the CFR ranged from 5.9 to 42.9%. CONCLUSIONS: A history of varicella, soft tissue infections, parameningeal infections and CSF leaks are important clinical clues to GAS in children with meningitis. Young children and hematogenic spread related cases need to be closely monitored for shock due to the high risk of death.

Preadmission course and management of severe pediatric group A streptococcal infections during the 2022-2023 outbreak: a single-center experience.

PURPOSE: The massive increase of infections with Group A Streptococcus (GAS) in 2022-2023 coincided in Switzerland with a change of the recommendations for the management of GAS pharyngitis. Therefore, the objective of the present study was to investigate whether the clinical manifestations and management before hospitalization for GAS infection differed in 2022-2023 compared with 2013-2022. METHODS: Retrospective study of GAS infections requiring hospitalization in patients below 16 years. Preadmission illness (modified McIsaac score), oral antibiotic use, and outcome in 2022-2023 were compared with 2013-2022. Time series were compared with surveillance data for respiratory viruses. RESULTS: In 2022-2023, the median modified McIsaac score was lower (2 [IQR 2-3] vs. 3 [IQR 2-4], p = < 0.0001) and the duration of preadmission illness was longer (4 days [3-7] vs. 3 [2-6], p = 0.004) than in 2013-2022. In both periods, withholding of preadmission oral antibiotics despite a modified McIsaac score ≥ 3 (12% vs. 18%, n.s.) or ≥ 4 (2.4% vs. 10.0%, p = 0.027) was rare. Respiratory disease, skeletal/muscle infection, and invasive GAS disease were significantly more frequent in 2022-2023, but there were no differences in clinical outcome. The time course of GAS cases in 2022-2023 coincided with the activity of influenza A/B. CONCLUSION: We found no evidence supporting the hypothesis that the 2022-2023 GAS outbreak was associated with a change in preadmission management possibly induced by the new recommendation for GAS pharyngitis. However, clinical manifestations before admission and comparative examination of time-series strongly suggest that viral co-circulation played an important role in this outbreak.

Epidemiology of scarlet fever in Victoria, Australia, 2007-2017.

In the last 10-15 years, there has been a global resurgence of scarlet fever, an infection historically associated with significant morbidity and mortality. It is unknown whether scarlet fever incidence has increased in Australia. We aimed to examine the incidence, predictors and severity of scarlet fever in the state of Victoria, Australia from 2007 to 2017, analyzing scarlet fever emergency department (ED) presentations, hospitalizations and deaths. Of the 1 578 scarlet fever cases during the study period, most occurred in children aged <10 years (1 344, 85%), in males (882, 56%), and during winter and spring months (918, 57%). There were no deaths with scarlet fever, however, 374 cases (24%) were admitted to hospital. The annual incidence of scarlet fever was stable during the study period (mean, 2.5; range, 1.9-3.1 cases per 100 000). Annual incidence was highest in children aged <5 years (19.3 per 100 000), and was 21% higher in males than females, adjusting for age and year (incidence rate ratio, 1.21, 95%CI 1.09-1.34). Whilst scarlet fever ED presentations and hospitalizations were stable in Victoria from 2007 to 2017, the recent identification of a Streptococcus pyogenes variant in Australia associated with epidemic scarlet fever overseas highlights the risk of future outbreaks.

State transitions across the Strep A disease spectrum: scoping review and evidence gaps.

The spectrum of diseases caused by Streptococcus pyogenes (Strep A) ranges from superficial to serious life-threatening invasive infections. We conducted a scoping review of published articles between 1980 and 2021 to synthesize evidence of state transitions across the Strep A disease spectrum. We identified 175 articles reporting 262 distinct observations of Strep A disease state transitions. Among the included articles, the transition from an invasive or toxin-mediated disease state to another disease state (i.e., to recurrent ARF, RHD or death) was described 115 times (43.9% of all included transition pairs) while the transition to and from locally invasive category was the lowest (n = 7; 0.02%). Transitions from well to any other state was most frequently reported (49%) whereas a relatively higher number of studies (n = 71) reported transition from invasive disease to death. Transitions from any disease state to locally invasive, Strep A pharyngitis to invasive disease, and chronic kidney disease to death were lacking. Transitions related to severe invasive diseases were more frequently reported than superficial ones. Most evidence originated from high-income countries and there is a critical need for new studies in low- and middle-income countries to infer the state transitions across the Strep A disease spectrum in these high-burden settings.