Mycobacterium ulcerans challenge strain selection for a Buruli ulcer controlled human infection model

Critical scientific questions remain regarding infection with Mycobacterium ulcerans, the organism responsible for the neglected tropical disease, Buruli ulcer (BU). A controlled human infection model has the potential to accelerate our knowledge of the immunological correlates of disease, to test prophylactic interventions and novel therapeutics. Here we present microbiological evidence supporting M. ulcerans JKD8049 as a suitable human challenge strain. This non-genetically modified Australian isolate is susceptible to clinically relevant antibiotics, can be cultured in animal-free and surfactant-free media, can be enumerated for precise dosing, and has stable viability following cryopreservation. Infectious challenge of humans with JKD8049 is anticipated to imitate natural infection, as M. ulcerans JKD8049 is genetically stable following in vitro passage and produces the key virulence factor, mycolactone. Also reported are considerations for the manufacture, storage, and administration of M. ulcerans JKD8049 for controlled human infection.

Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review

The high strain diversity of Streptococcus pyogenes serves as a major obstacle to vaccine development against this leading global pathogen. We did a systematic review of studies in PubMed, MEDLINE, and Embase that reported the global distribution of S pyogenes emm-types and emm-clusters from Jan 1, 1990, to Feb 23, 2023. 212 datasets were included from 55 countries, encompassing 74 468 bacterial isolates belonging to 211 emm-types. Globally, an inverse correlation was observed between strain diversity and the UNDP Human Development Index (HDI; r=-0·72; p<0·0001), which remained consistent upon subanalysis by global region and site of infection. Greater strain diversity was associated with a lower HDI, suggesting the role of social determinants in diseases caused by S pyogenes. We used a population-weighted analysis to adjust for the disproportionate number of epidemiological studies from high-income countries and identified 15 key representative isolates as vaccine targets. Strong strain type associations were observed between the site of infection (invasive, skin, and throat) and several streptococcal lineages. In conclusion, the development of a truly global vaccine to reduce the immense burden of diseases caused by S pyogenes should consider the multidimensional diversity of the pathogen, including its social and environmental context, and not merely its geographical distribution.

Pre-extensively Drug-Resistant Congenital Tuberculosis in an Extremely Premature Baby

We describe a case of congenital tuberculosis in an extremely premature baby, with rapid molecular detection of a pre-extensively drug-resistant (XDR) pattern of drug resistance. The baby was treated successfully with a regimen including bedaquline and delamanid, drugs not previously described in the treatment of congenital tuberculosis (TB).

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

Background

Increases in invasive group A streptococcal disease (iGAS) have recently been reported in multiple countries in the northern hemisphere, occurring during, and outside of, typical spring peaks. We report the epidemiology of iGAS among children in Australia from 1 July 2018 to 31 December 2022.

Methods

The Paediatric Active Enhanced Disease Surveillance (PAEDS) Network prospectively collected iGAS patient notifications for children and young people aged less than 18 years admitted to five major Australian paediatric hospitals in Victoria, Queensland, Western Australia and the Northern Territory. Patients were eligible for inclusion if they had GAS isolated from a normally sterile body site, or met clinical criteria for streptococcal toxic shock syndrome or necrotising fasciitis with GAS isolated from a non-sterile site. We report patients' clinical and demographic characteristics, and estimate minimum incidence rates.

Findings

We identified 280 paediatric iGAS patients, median age 4.5 years (interquartile range 1.4-6.4). We observed a pre-pandemic peak annualised incidence of 3.7 per 100,000 (95% CI 3.1-4.4) in the 3rd quarter of 2018, followed by a decline to less than 1.0 per 100,000 per quarter from 2020 to mid-2021. The annualised incidence increased sharply from mid-2022, peaking at 5.2 per 100,000 (95% CI 4.4-6.0) in the 3rd quarter and persisting into the 4th quarter (4.9 per 100,000, 95% CI 4.2-5.7). There were 3 attributable deaths and 84 (32%) patients had severe disease (overall case fatality rate 1%, 95% CI 0.2-3.3). Respiratory virus co-infection, positive in 57 of 119 patients tested, was associated with severe disease (RR 1.9, 95% CI 1.2-3.0). The most common emm-type was emm-1 (60 of 163 isolates that underwent emm-typing, 37%), followed by emm-12 (18%).

Interpretation

Australia experienced an increase in the incidence of iGAS among children and young people in 2022 compared to pandemic years 2020-2021. This is similar to northern hemisphere observations, despite differences in seasons and circulating respiratory viruses. Outbreaks of iGAS continue to occur widely. This emphasises the unmet need for a vaccine to prevent significant morbidity associated with iGAS disease.

Funding

Murdoch Children's Research Institute funded open access publishing of this manuscript.

Strategic and scientific contributions of human challenge trials for vaccine development: facts versus fantasy

The unprecedented speed of delivery of SARS-CoV-2 pandemic vaccines has redefined the limits for all vaccine development. Beyond the aspirational 100-day timeline for tomorrow's hypothetical pandemic vaccines, there is a sense of optimism that development of other high priority vaccines can be accelerated. Early in the COVID-19 pandemic, an intense and polarised academic and public discourse arose concerning the role of human challenge trials for vaccine development. A case was made for human challenge trials as a powerful tool to establish early proof-of-concept of vaccine efficacy in humans, inform vaccine down selection, and address crucial knowledge gaps regarding transmission, pathogenesis, and immune protection. We review the track record of human challenge trials contributing to the development of vaccines for 19 different pathogens and discuss relevant limitations, barriers, and pitfalls. This Review also highlights opportunities for efforts to broaden the scope and boost the effects of human challenge trials, to accelerate all vaccine development.

Naturally acquired functional antibody responses to group A Streptococcus differ between major strain types

Group A Streptococcus (GAS) is a leading human pathogen for which there is no licensed vaccine. Infections are most common in young children and the elderly suggesting immunity accumulates with exposure until immune senescence in older age. Though protection has been postulated to be strain type specific, based on the M-protein (emm-type), the antigenic basis of population-level immunity remains poorly understood. Naturally acquired GAS antibody responses were investigated using intravenous immunoglobulin (IVIG), which contains pooled immunoglobulins from thousands of healthy human donors, as a surrogate for population immunity. Functional opsonophagocytic killing assays were conducted with GAS strains (n = 6) representing the three major emm-pattern types (emm12, A-C pattern; emm53, D-pattern; and emm75, E-pattern). While IVIG induced opsonophagocytic killing of all GAS strains tested, specificity assays showed the profile of protective antibodies differed considerably between emm-types. Antibodies targeting the M-protein were a major component of the functional IVIG antibody response for emm12 and emm53 strains but not for emm75 strains. The striking differences in the contribution of M-protein specific antibodies to killing suggest naturally acquired immunity differs between strains from the major emm-patterns. This challenges the dogma that M-protein is the primary protective antigen across all GAS straintypes. IMPORTANCE Group A Streptococcus (GAS) is a globally important pathogen. With the surge of invasive GAS infections that have occurred in multiple countries, contemporaneous with the relaxation of COVID-19 pandemic restrictions, there is increased interest in the mechanisms underpinning GAS immunity. We utilized intravenous immunoglobulin (IVIG), pooled immunoglobulins from thousands of healthy donors, as a surrogate for population-level immunity to GAS, and explored the contribution of strain-specific (M-type specific) antibodies to GAS immunity using functional killing assays. This revealed striking differences between major strain types as to the contribution of strain specific antibodies to killing. For GAS strains belonging to the E pattern group, M-type specific antibodies do not mediate killing and immunity, which contrasts with strains belonging to pattern A-C and D groups. This challenges the historical dogma, originally proposed by Rebecca Lancefield in the 1950-1960s, that the M-protein is the major protective antigen across all GAS strain types.

A qualitative investigation of paediatric intensive care staff attitudes towards the diagnosis of lower respiratory tract infection in the molecular diagnostics era

Background

In the past decade, molecular diagnostic syndromic arrays incorporating a range of bacterial and viral pathogens have been described. It is unclear how paediatric intensive care unit (PICU) staff diagnose lower respiratory tract infection (LRTI) and integrate diagnostic array results into antimicrobial decision-making.

Methods

An online survey with eleven questions was distributed throughout paediatric intensive care societies in the UK, continental Europe and Australasia with a total of 755 members. Participants were asked to rate the clinical factors and investigations they used when prescribing for LRTI. Semi-structured interviews were undertaken with staff who participated in a single-centre observational study of a 52-pathogen diagnostic array.

Results

Seventy-two survey responses were received; most responses were from senior doctors. Whilst diagnostic arrays were used less frequently than routine investigations (i.e. microbiological culture), they were of comparable perceived utility when making antimicrobial decisions. Prescribers reported that for arrays to be clinically impactful, they would need to deliver results within 6 h for stable patients and within 1 h for unstable patients to inform their immediate decision to prescribe antimicrobials. From 16 staff interviews, we identified that arrays were helpful for the diagnosis and screening of bacterial LRTI. Staff reported it could be challenging to interpret results in some cases due to the high sensitivity of the test. Therefore, results were considered within the context of the patient and discussed within the multidisciplinary team.

Conclusions

Diagnostic arrays were considered of comparable value to microbiological investigations by PICU prescribers. Our findings support the need for further clinical and economic evaluation of diagnostic arrays in a randomised control trial.

Trial registration

Clinicaltrials.gov, NCT04233268. Registered on 18 January 2020.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44253-023-00008-z.

A human model of Buruli ulcer: The case for controlled human infection and considerations for selecting a Mycobacterium ulcerans challenge strain

Critical knowledge gaps regarding infection with Mycobacterium ulcerans, the cause of Buruli ulcer (BU), have impeded development of new therapeutic approaches and vaccines for prevention of this neglected tropical disease. Here, we review the current understanding of host-pathogen interactions and correlates of immune protection to explore the case for establishing a controlled human infection model of M. ulcerans infection. We also summarise the overarching safety considerations and present a rationale for selecting a suitable challenge strain.

Geographic Expansion of Japanese Encephalitis Virus to Australia: Neuroinflammatory Sequelae and Consideration of Immunomodulation

We report a child from Southern Australia (New South Wales) who presented during a La Niña event with encephalopathy and acute flaccid paralysis. Magnetic resonance imaging suggested Japanese encephalitis (JE). Steroids and intravenous immunoglobulin did not improve symptoms. Therapeutic plasma exchange (TPE) resulted in rapid improvement and tracheostomy decannulation. Our case illustrates the complex pathophysiology of JE, its' geographic expansion into Southern Australia and potential use of TPE for neuroinflammatory sequelae.

Pediatric Hepatitis and Respiratory Viruses: A Spatiotemporal Ecologic Analysis

INTRODUCTION

Beginning in early 2022, clusters of severe pediatric hepatitis were reported in Europe and the United States. To date, no cause has been identified although human adenovirus 41 has been proposed in a proportion of cases. We examined population data >11 years for hepatitis clusters in Victoria, Australia, and whether any were spatiotemporally associated with community transmission of common respiratory viruses.

METHODS

We used SaTScan to analyze for clusters of pediatric hepatitis and respiratory adenoviruses in Victoria. Negative binomial regression analysis was performed to determine any associations between hepatitis and respiratory viruses across Victoria between July 1, 2011, and June 30, 2022.

RESULTS

A number of positive associations were observed in Victoria between pediatric hepatitis clusters and respiratory viruses in our spatiotemporal analysis. A positive association was not found with respiratory adenoviruses or SARS-CoV-2. Increased hepatitis clusters were observed in 2021 and 2022 as noted internationally.

CONCLUSION

The current hepatitis outbreak is novel and, although respiratory viruses are broadly associated with hepatitis, SARS-CoV-2 and respiratory adenoviruses are unlikely to be related.

A Systematic Review of Human Challenge Trials, Designs, and Safety

BACKGROUND

Few studies have assessed participant safety in human challenge trials (HCTs). Key questions regarding HCTs include how risky such trials have been, how often adverse events (AEs) and serious adverse events (SAEs) occur, and whether risk mitigation measures have been effective.

METHODS

A systematic search of PubMed and PubMed Central for articles reporting on results of HCTs published between 1980 and 2021 was performed and completed by 7 October 2021.

RESULTS

Of 2838 articles screened, 276 were reviewed in full. A total of 15 046 challenged participants were described in 308 studies that met inclusion criteria; 286 (92.9%) of these studies reported mitigation measures used to minimize risk to the challenge population. Among 187 studies that reported on SAEs, 0.2% of participants experienced at least 1 challenge-related SAE. Among 94 studies that graded AEs by severity, challenge-related AEs graded "severe" were reported by between 5.6% and 15.8% of participants. AE data were provided as a range to account for unclear reporting. Eighty percent of studies published after 2010 were registered in a trials database.

CONCLUSIONS

HCTs are increasingly common and used for an expanding list of diseases. Although AEs occur, severe AEs and SAEs are rare. Reporting has improved over time, though not all papers provide a comprehensive report of relevant health impacts. We found very few severe symptoms or SAEs in studies that reported them, but many HCTs did not report relevant safety data. This study was preregistered on PROSPERO as CRD42021247218.

Acute rheumatic fever and rheumatic heart disease in children and adolescents in Victoria, Australia

AIM

To describe the epidemiology and clinical profile of children and adolescents with acute rheumatic fever (ARF) and rheumatic heart disease (RHD) in Victoria, Australia.

METHODS

A retrospective audit was undertaken of children and adolescents with ARF and RHD attending the Royal Children's and Monash Children's Hospitals in Victoria, Australia between 2010 and 2019. Potential cases were identified by searching multiple sources for relevant ICD-10-AM codes and keywords, then reviewed manually. For confirmed cases, we collected data on patient demographics, clinical features, comorbidities and management.

RESULTS

Of 179 participants included, there were 108 Victorian residents and 71 non-Victorian residents. 126 had at least one episode of ARF during the study period and 128 were diagnosed with RHD. In the Victorian resident group, the overall incidence of ARF was 0.8 per 100 000 5-14 year olds. This incidence was higher in Victorian Aboriginal and/or Torres Strait Islander (3.8 per 100 000) and Pacific Islander (32.1 per 100 000) sub-populations. Of 83 Victorian residents who had an ARF episode, 11 (13%) had a recurrence. Most Victorian residents with RHD had mixed aortic and mitral valve pathology (69.4%) and moderate to severe disease (61.9%). Most non-Victorian residents were Aboriginal and/or Torres Strait Islander people (80.3%) and were commonly transferred for tertiary or surgical management of RHD (83.1%).

CONCLUSIONS

ARF and RHD continue to affect the health of significant numbers of children and adolescents living in Victoria, including severe and recurrent disease. Specialised services and a register-based control program may help to prevent complications and premature death.

Using a bedside test to detect genetic susceptibility to aminoglycoside-induced hearing loss: Has the future arrived?

Aminoglycosides are among the most commonly prescribed antibiotics in hospitalised Australian adults and children. A proportion of individuals with an underlying genetic predisposition to aminoglycoside-induced hearing loss (AIHL) can develop bilateral sensorineural hearing loss that is immediate and profound after just a single standard dose of an aminoglycoside. A recent publication described the use of a rapid point-of-care test (POCT) in a neonatal nursery in the United Kingdom for real-time detection of infants at risk of AIHL, in whom exposure to aminoglycosides could then be avoided. This proof of concept study should provide a catalyst for further development of similar assays that would be suitable for Australia's genetically diverse population. The barriers to mitigating the impact of AIHL on Australian children are not primarily technical, but involve a lack of data on the prevalence of the MT-RNR1 mutations in our current neonatal and paediatric populations and intensive care nurseries.

Guillain-Barré syndrome temporally associated with COVID-19 vaccines in Victoria, Australia

Guillain-Barré syndrome (GBS) is an adverse event of special interest (AESI) for surveillance systems monitoring adverse events following immunisation (AEFI) with COVID-19 vaccines. Emerging data support a temporal association between GBS and adenovirus-vector COVID-19 vaccines. We present a case series of GBS reports submitted between February and November 2021 to our enhanced spontaneous surveillance system (SAEFVIC) in Victoria, Australia, following vaccination with either the adenovirus-vector vaccine Vaxzevria ChadOx1-S (AstraZeneca) or an mRNA vaccine (Comirnaty BNT162b2 [Pfizer-BioNTech] or Spikevax mRNA-1273 [Moderna]). For each report, Brighton Collaboration case definitions were used to describe diagnostic certainty. Severity was graded using the GBS Disability Score. The observed incidence of GBS following immunisation against COVID-19 was compared to expected background ICD10-AM G61.0 coded hospitalisations. There were 41 total cases of GBS reported to SAEFVIC following Vaxzevria (n = 38), Comirnaty (n = 3), or Spikevax (n = 0) vaccines. The observed GBS incidence rate exceeded the expected background rate for Vaxzevria only, with 1.85 reports per 100,000 doses following dose 1, higher than the expected rate of 0.39 hospital admissions per 100,000 adults within 42 days of vaccination. Of 38 GBS reports following Vaxzevria, the median age at vaccination was 66 years and median onset of symptoms was 14 days following immunisation. There was one death. Four cases initially categorised as GBS were later reclassified as acute-onset chronic inflammatory demyelinating polyneuropathy. Fatigue was the predominant persisting symptom reported at follow up. Additional global studies are required to characterise risk factors, clinical variability, and to provide precision and generalizability regarding AEFI risks such as GBS associated with different vaccine platforms, which will help inform communication of the potential benefits and risks of COVID19 vaccination.

Study protocol for controlled human infection for penicillin G against Streptococcus pyogenes: a double-blinded, placebo-controlled, randomised trial to determine the minimum concentration required to prevent experimental pharyngitis (the CHIPS trial)

INTRODUCTION

Regular intramuscular benzathine penicillin G injections have been the cornerstone of rheumatic heart disease (RHD) secondary prophylaxis since the 1950s. As the pharmacological correlate of protection remains unknown, it is difficult to recommend changes to this established regimen. Determining the minimum effective penicillin exposure required to prevent Streptococcus pyogenes infection will accelerate development of new long-acting penicillins for RHD prevention as well as inform opportunities to improve existing regimens. The CHIPS trial will address this knowledge gap by directly testing protection afforded by different steady state plasma concentrations of penicillin in an established model of experimental human S. pyogenes pharyngitis.

METHODS AND ANALYSIS

This is a double-blinded, placebo-controlled, randomised experimental human infection study. Sixty healthy adult volunteers aged 18-40 years will be recruited and randomised 1:1:1:1:1 to continuous intravenous penicillin infusions targeting five different steady state plasma concentrations of 0 (placebo), 3, 6, 12 and 20 ng/mL via a midline catheter. Each participant's penicillin pharmacokinetic parameters will be established prior to the challenge, to ensure accurate dosing for the continuous infusion. Following the challenge with a well-characterised strain of S. pyogenes, participants will be observed for up to 6 days for the development of pharyngitis and treated with antibiotics prior to discharge. The primary objective is to determine the minimum effective steady-state plasma penicillin concentration required to prevent experimental pharyngitis. Secondary objectives will explore systemic and mucosal immunoinflammatory responses during pharyngitis, bacterial colonisation dynamics, environmental contamination and qualitative evaluation of the participant experience.

ETHICS AND DISSEMINATION

Ethical approval has been obtained (Bellberry Human Research Ethics Committee). Findings will be reported in peer-reviewed publications and presented at national/international stakeholder forums.

TRIAL REGISTRATION NUMBER

ACTRN12621000751875.

Characteristics, management and changing incidence of children with empyema in a paediatric intensive care unit

AIM

Paediatric intensive care unit (PICU) admissions for empyema increased following the 13-valent pneumococcal conjugate vaccine (PCV13). We describe the clinical characteristics, management and outcomes for children with empyema and compare incidence before and after PCV13.

METHODS

Retrospective study of patients <18 years admitted to The Royal Children's Hospital Melbourne PICU with empyema between January 2016 and July 2019. We investigated the incidence of empyema during two time periods: 2007-2010 (pre-PCV13) and 2016-2019 (post-PCV13).

RESULTS

Seventy-one children (1.9% of all PICU admissions) were admitted to PICU with empyema between 2016 and 2019. Sixty-one (86%) had unilateral disease, 11 (16%) presented with shock and 44 (62%) were ventilated. Streptococcus pneumoniae and group A Streptococcus were the most commonly identified pathogens. Forty-five (63%) were managed with video-assisted thoracoscopic surgery (VATS). There was a 31% reduction in empyema hospitalisations as a proportion of all hospitalisations (IRR 0.69, 95% CI 0.59-0.8), but a 2.8-fold increase in empyema PICU admissions as a proportion of all PICU admissions (95% CI 2.2-3.5, P < 0.001). For the PICU cohort, this was accompanied by reduction in PIM2 probability of death (median 1% vs. 1.9%, P = 0.02) and duration of intubation (median 69 h vs. 126.5 h, P = 0.045).

CONCLUSIONS

In children with empyema in PICU 62% required ventilation, 16% had features of shock and 63% received VATS. Empyema admissions, as a proportion of all PICU admissions, increased in the era post-PCV13 compared to pre-PCV13 despite no increase in illness severity at admission.

Immune signature of acute pharyngitis in a Streptococcus pyogenes human challenge trial

Streptococcus pyogenes causes at least 750 million infections and more than 500,000 deaths each year. No vaccine is currently available for S. pyogenes and the use of human challenge models offer unique and exciting opportunities to interrogate the immune response to infectious diseases. Here, we use high-dimensional flow cytometric analysis and multiplex cytokine and chemokine assays to study serial blood and saliva samples collected during the early immune response in human participants following challenge with S. pyogenes. We find an immune signature of experimental human pharyngitis characterised by: 1) elevation of serum IL-1Ra, IL-6, IFN-γ, IP-10 and IL-18; 2) increases in peripheral blood innate dendritic cell and monocyte populations; 3) reduced circulation of B cells and CD4+ T cell subsets (Th1, Th17, Treg, TFH) during the acute phase; and 4) activation of unconventional T cell subsets, γδTCR + Vδ2+ T cells and MAIT cells. These findings demonstrate that S. pyogenes infection generates a robust early immune response, which may be important for host protection. Together, these data will help advance research to establish correlates of immune protection and focus the evaluation of vaccines.

Infliximab for Paradoxical Reactions in Pediatric Central Nervous System Tuberculosis

Paradoxical reactions in central nervous system tuberculosis (CNS-TB) are associated with significant morbidity and mortality. We describe 4 HIV-uninfected children treated for CNS-TB with severe paradoxical reactions unresponsive to corticosteroids. All made recovery after treatment with infliximab, highlighting the safety and effectiveness of infliximab for this complication, and need for prospective trials.

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

BACKGROUND

Streptococcus pyogenes is a leading cause of infection-related morbidity and mortality. A reinvigorated vaccine development effort calls for new clinically relevant human S pyogenes experimental infection models to support proof of concept evaluation of candidate vaccines. We describe the initial Controlled Human Infection for Vaccination Against S pyogenes (CHIVAS-M75) study, in which we aimed to identify a dose of emm75 S pyogenes that causes acute pharyngitis in at least 60% of volunteers when applied to the pharynx by swab.

METHODS

This observational, dose-finding study was done in a clinical trials facility in Melbourne (VIC, Australia). Groups of healthy volunteers aged 18-40 years, at low risk of complicated S pyogenes disease, and without high type-specific anti-emm75 IgG antibodies against the challenge strain were challenged and closely monitored as inpatients for up to 6 days, and then as outpatients for 6 months. Antibiotics were started upon diagnosis (clinical signs and symptoms of pharyngitis and a positive rapid molecular test) or after 5 days in those without pharyngitis. Rapid test results were confirmed by standard bacterial culture. After a sentinel participant, cohorts of five and then ten participants were challenged, with protocol-directed dose-escalation or de-escalation for subsequent cohorts. The primary outcome was the proportion of participants at each dose level with pharyngitis by day 5 after challenge. The study is registered with ClinicalTrials.gov, NCT03361163.

FINDINGS

Between July 10, 2018, and Sept 23, 2019, 25 healthy adults were challenged with emm75 S pyogenes and included in analyses. Pharyngitis was diagnosed in 17 (85%; 95% CI 62-97) of 20 participants at the starting dose level (1-3 × 10⁵ colony-forming units [CFU]/mL). This high proportion prompted dose de-escalation. At the lower dose level (1-3 × 10⁴ CFU/mL), pharyngitis was diagnosed in one of five participants. Immunological, biochemical, and microbiological results supported the clinical picture, with acute symptomatic pharyngitis characterised by pharyngeal colonisation by S pyogenes accompanied by significantly elevated C-reactive protein and inflammatory cytokines (eg, interferon-γ and interleukin-6), and modest serological responses to streptolysin O and deoxyribonuclease B. There were no severe (grade 3) or serious adverse events related to challenge.

INTERPRETATION

We have established a reliable pharyngitis human infection model with reassuring early safety findings to accelerate development of vaccines and other interventions to control disease due to S pyogenes.

FUNDING

Australian National Health and Medical Research Council.

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

BACKGROUND

Streptococcus pyogenes causes a profound global burden of morbidity and mortality across its diverse clinical spectrum. To support a new controlled human infection ('challenge') model seeking to accelerate S. pyogenes vaccine development, we aimed to develop an accurate and reliable molecular method for quantifying bacterial load from pharyngeal swabs collected during experimental human pharyngitis.

METHODS

Combined sequential RNA + DNA extraction from throat swabs was compared to traditional separate RNA-only and DNA-only extractions. An emm-type specific qPCR was developed to detect the emm75 challenge strain. Results from the qPCR were compared to culture, using throat swab samples collected in a human challenge study.

RESULTS

The qPCR was 100% specific for the emm75 challenge strain when tested against a panel of S. pyogenes emm-types and other respiratory pathogens. Combined RNA + DNA extraction had similar yield to traditional separate extractions. The combined extraction method and emm75 qPCR had 98.8% sensitivity compared to culture for throat swabs collected from challenge study participants.

CONCLUSIONS

We have developed a reliable molecular method for measuring S. pyogenes bacterial load from throat swabs collected in a controlled human infection model of S. pyogenes pharyngitis.

TRIAL REGISTRATION

NCT03361163 on 4th December 2017.

COVID-19 and complicated bacterial pneumonia in children

We read with great interest the recent publication by Steinfortet al. [1] outlining the profound reduction in influenza infections in Australia as a result of social distancing during the COVID-19 pandemic. Similar dramatic effects of social distancing on paediatric hospital activity have been reported, with reduced hospital admissions, presentations for respiratory conditions and detection of other viruses [2–6]. However, the impact of the pandemic on bacterial respiratory infections has not been well characterised. The Australian state of Victoria (population 6.7 million) has experienced a prolonged period of social restrictions (“lockdown”) since March 2020. This period spanned the southern hemisphere autumn to spring, the usual peak period for bacterial respiratory infections.

Social distancing measures instituted due to #SARSCoV2 have dramatically reduced paediatric thoracic empyema cases in Australiahttps://bit.ly/3akG98M

Payment in challenge studies: ethics, attitudes and a new payment for risk model

Controlled Human Infection Model (CHIM) research involves the infection of otherwise healthy participants with disease often for the sake of vaccine development. The COVID-19 pandemic has emphasised the urgency of enhancing CHIM research capability and the importance of having clear ethical guidance for their conduct. The payment of CHIM participants is a controversial issue involving stakeholders across ethics, medicine and policymaking with allegations circulating suggesting exploitation, coercion and other violations of ethical principles. There are multiple approaches to payment: reimbursement, wage payment and unlimited payment. We introduce a new Payment for Risk Model, which involves paying for time, pain and inconvenience and for risk associated with participation. We give philosophical arguments based on utility, fairness and avoidance of exploitation to support this. We also examine a cross-section of the UK public and CHIM experts. We found that CHIM participants are currently paid variable amounts. A representative sample of the UK public believes CHIM participants should be paid approximately triple the UK minimum wage and should be paid for the risk they endure throughout participation. CHIM experts believe CHIM participants should be paid more than double the UK minimum wage but are divided on the payment for risk. The Payment for Risk Model allows risk and pain to be accounted for in payment and could be used to determine ethically justifiable payment for CHIM participants.Although many research guidelines warn against paying large amounts or paying for risk, our empirical findings provide empirical support to the growing number of ethical arguments challenging this status quo. We close by suggesting two ways (value of statistical life or consistency with risk in other employment) by which payment for risk could be calculated.

Incidence of acute rheumatic fever and rheumatic heart disease in Melbourne, Australia from 1937 to 2013

AIM

Acute rheumatic fever (ARF) most commonly presents in children aged 5-14 years old. Lifelong rheumatic heart disease (RHD) can result. This study investigated time trends in ARF and RHD using inpatient data from the Royal Children's Hospital, Melbourne (RCH).

METHODS

A retrospective cohort study covering the period 1937-2013 was conducted using records from RCH, a quaternary paediatric hospital in Melbourne, Victoria, Australia. Patient data were identified using RCH classification of diseases coding for ARF or RHD for years <1952. For the period 1952-1987, this system was used in addition to identifying International Classification of Disease (ICD) discharge codes that corresponded to ARF or RHD. From 1988-2013, only ICD codes were used to identify patient data. Descriptive epidemiological analyses were performed, including incidence rate calculations using historical census population denominator data. Analyses focussed on children in the peak age group.

RESULTS

Among children aged five to 14 years, a total of 4337 RCH admissions with ARF/RHD occurred for 3015 patients. A sharp decline in first ARF/RHD hospitalisations at RCH occurred from 1959, following a peak mean annual incidence rate during 1944-1947 of 40.1/100 000 children (95% confidence interval (CI): 36.6-43.9; P < 0.05). Over 1996-2013, the mean annual incidence rate was 1.6/100 000 (95% CI: 1.3-1.8) and reached 2.3/100 000 (95% CI: 1.3-3.7) in 2005.

CONCLUSION

The burden of ARF and RHD treated at RCH declined following the 1940s, mirroring changes seen in North America and Europe. Despite this, inpatient treatment for these conditions continued to be provided right up until the end of the study period.

Controlled human infection for vaccination against Streptococcus pyogenes (CHIVAS): Establishing a group A Streptococcus pharyngitis human infection study

Group A Streptococcus (GAS) is a highly-adapted and human-restricted pathogen responsible for a high global burden of disease across a diverse clinical spectrum. Vaccine development has been impeded by scientific, regulatory, and commercial obstacles. Human infection studies (HIS) are increasingly contributing to drug, diagnostics, and vaccine development, reducing uncertainty at early stages, especially for pathogens with animal models that incompletely reproduce key elements of human disease. We review the small number of historical GAS HIS and present the study protocol for a dose-ranging inpatient study in healthy adults. The primary objective of the study is to establish a new GAS pharyngitis HIS with an attack rate of at least 60% as a safe and reliable platform for vaccine evaluation and pathogenesis research. According to an adaptive dose-ranging study design, emm75 GAS doses manufactured in keeping with principles of Good Manufacturing Practice will be directly applied by swab to the pharynx of carefully screened healthy adult volunteers at low risk of severe complicated GAS disease. Participants will remain as closely monitored inpatients for up to six days, observed for development of the primary outcome of acute symptomatic pharyngitis, as defined by clinical and microbiological criteria. All participants will be treated with antibiotics and followed as outpatients for six months. An intensive sampling schedule will facilitate extensive studies of host and organism dynamics during experimental pharyngitis. Ethics approval has been obtained and the study has been registered at ClinicalTrials.gov (NCT03361163).

Potential for Molecular Testing for Group A Streptococcus to Improve Diagnosis and Management in a High-Risk Population: A Prospective Study

Background

In high-burden settings, guidelines recommend antibiotic treatment for all suspected group A Streptococcus (GAS) infections to prevent rheumatic fever and poststreptococcal glomerulonephritis. Highly sensitive rapid GAS tests could reduce unnecessary antibiotic use in these settings.

Methods

This was a prospective study of the Xpert Xpress Strep A (Cepheid) molecular test compared with culture of throat swab samples collected at a referral hospital in northern Australia. Demographic and clinical data and results of streptococcal serology and culture were collected.

Results

Of 164 throat swab samples, 145 (88%) were eligible for inclusion; 49 (34%) were molecular test positive and 24 (17%) were culture positive for GAS. The sensitivity, specificity, and positive and negative predictive values for the molecular test versus culture were 100.0%, 79.3%, 48.8%, and 100.0%, respectively. Among 25 samples testing positive with the molecular test and negative with culture, group C or G streptococci were cultured in 2, and a plausible clinical explanation, such as pharyngotonsillitis, or rheumatic fever with positive results of streptococcal serology, was apparent in 19 instances. In 25 patients with rheumatic fever or poststreptococcal glomerulonephritis diagnoses, molecular testing nearly trebled the detection of GAS in throat swab samples, from 3 (12%) detected with culture to 8 (32%) detected with molecular testing. Reasons for “false-positive” molecular test results could include the presence of GAS below the threshold of culture detection or persistence of nonviable organisms after infection.

Conclusion

Implementation of molecular testing could improve antibiotic use in this high-burden setting. The incremental yield in poststreptococcal syndromes, by which time cultures are negative, has high potential in the diagnostic workup of autoimmune poststreptococcal syndromes and warrants further investigation.

A Controlled Human Infection Model of Group A Streptococcus Pharyngitis: Which Strain and Why?

Group A Streptococcus (GAS) is a major cause of global infection-related morbidity and mortality. A modern controlled human infection model (CHIM) of GAS pharyngitis can accelerate vaccine development and pathogenesis research. A robust rationale for strain selection is central to meeting ethical, scientific, and regulatory requirements. Multifaceted characterization studies were done to compare a preferred candidate emm75 (M75) GAS strain to three other strains: an alternative candidate emm12 (M12) strain, an M1 strain used in 1970s pharyngitis CHIM studies (SS-496), and a representative (5448) of the globally disseminated M1T1 clone. A range of approaches were used to explore strain growth, adherence, invasion, delivery characteristics, short- and long-term viability, phylogeny, virulence factors, vaccine antigens, resistance to killing by human neutrophils, and lethality in a murine invasive model. The strains grew reliably in a medium without animal-derived components, were consistently transferred using a swab method simulating the CHIM protocol, remained viable at -80°C, and carried genes for most candidate vaccine antigens. Considering GAS molecular epidemiology, virulence factors, in vitro assays, and results from the murine model, the contemporary strains show a spectrum of virulence, with M75 appearing the least virulent and 5448 the most. The virulence profile of SS-496, used safely in 1970s CHIM studies, was similar to that of 5448 in the animal model and virulence gene carriage. The results of this multifaceted characterization confirm the M75 strain as an appropriate choice for initial deployment in the CHIM, with the aim of safely and successfully causing pharyngitis in healthy adult volunteers.IMPORTANCE GAS (Streptococcus pyogenes) is a leading global cause of infection-related morbidity and mortality. A modern CHIM of GAS pharyngitis could help to accelerate vaccine development and drive pathogenesis research. Challenge strain selection is critical to the safety and success of any CHIM and especially so for an organism such as GAS, with its wide strain diversity and potential to cause severe life-threatening acute infections (e.g., toxic shock syndrome and necrotizing fasciitis) and postinfectious complications (e.g., acute rheumatic fever, rheumatic heart disease, and acute poststreptococcal glomerulonephritis). In this paper, we outline the rationale for selecting an emm75 strain for initial use in a GAS pharyngitis CHIM in healthy adult volunteers, drawing on the findings of a broad characterization effort spanning molecular epidemiology, in vitro assays, whole-genome sequencing, and animal model studies.

International survey of paediatric infectious diseases consultants on the management of community-acquired pneumonia complicated by pleural empyema

AIM

Community-acquired pneumonia (CAP) complicated by pleural empyema is an important paediatric problem. Antibiotic management decisions are made on the basis of little available data and without strong specific recommendations in guidelines.

METHODS

This was an online survey of paediatric infectious diseases (PID) physicians disseminated by major international professional organisations, examining empiric and targeted antibiotic choice, switch to oral antibiotics and duration of treatment for two hypothetical cases of contrasting severity.

RESULTS

This study included 183 responses, mostly from North America, Western Europe and Australia/New Zealand. Increased disease severity was significantly associated with broader-spectrum and combination empiric and targeted antibiotic treatment, empiric methicillin-resistant Staphylococcus aureus (MRSA) coverage and both longer intravenous (IV) and total duration of antibiotic treatment. Empirical MRSA coverage was also associated with local prevalence. Clinical progress was most important for determining the timing of the switch from IV to oral antibiotics. Few respondents chose antibiotics with activity against organisms associated with atypical pneumonia (e.g. Mycoplasma, Chlamydia), and most did not choose agents that inhibit protein synthesis (e.g. clindamycin), even in the case of a severe invasive group A streptococcal infection. Some variation in targeted treatment choices reflected areas of uncertainty, such as Streptococcus pneumoniae susceptibility breakpoints, comparative effectiveness of anti-staphylococcal penicillins and first-generation cephalosporins for serious S. aureus infections and linezolid and vancomycin for MRSA pneumonia.

CONCLUSIONS

This international survey of PID physicians highlights the priority targets for clinical research to improve antibiotic treatment of CAP complicated by empyema. Interventions that might be studied include empirical antibiotic guidelines stratified by case severity, adjunctive empirical use of agents that inhibit protein synthesis (e.g. clindamycin) and approaches to encourage rapid IV-to-oral switch and shorter total antibiotic treatment.

Antibiotic duration and timing of the switch from intravenous to oral route for bacterial infections in children: systematic review and guidelines

Few studies are available to inform duration of intravenous antibiotics for children and when it is safe and appropriate to switch to oral antibiotics. We have systematically reviewed antibiotic duration and timing of intravenous to oral switch for 36 paediatric infectious diseases and developed evidence-graded recommendations on the basis of the review, guidelines, and expert consensus. We searched databases and obtained information from references identified and relevant guidelines. All eligible studies were assessed for quality. 4090 articles were identified and 170 studies were included. Evidence relating antibiotic duration to outcomes in children for some infections was supported by meta-analyses or randomised controlled trials; in other infections data were from retrospective series only. Criteria for intravenous to oral switch commonly included defervescence and clinical improvement with or without improvement in laboratory markers. Evidence suggests that intravenous to oral switch can occur earlier than previously recommended for some infections. We have synthesised recommendations for antibiotic duration and intravenous to oral switch to support clinical decision making and prospective research.