Group A Streptococcal Carriage and Seroepidemiology in Children up to 10 Years of Age in Australia

Nasopharyngeal carriage, antimicrobial susceptibility patterns, and associated factors of Gram-positive bacteria among children attending the outpatient department at the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia

BACKGROUND

Gram-positive bacteria residing in the nasopharynx can lead to severe illnesses in children, such as otitis media, pneumonia, and meningitis. Despite the potential threat, there is a lack of comprehensive data regarding the carriage rates of these bacteria among children in outpatient departments in the study area.

OBJECTIVE

This study aimed to assess the nasopharyngeal carriage, antimicrobial resistance patterns, and associated factors of Gram-positive bacteria among children attending the outpatient department at the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia.

METHODS

A hospital-based cross-sectional study was conducted from May 1, 2023, to August 30, 2023. A total of 424 nasopharyngeal swab samples were collected using sterile nasopharyngeal swabs, inoculated on Blood Agar and Mannitol Salt Agar plates, and identified through colony morphology, Gram stain, and biochemical tests. Antimicrobial susceptibility of the identified bacterial isolates was determined employing both the Kirby-Bauer and modified Kirby-Bauer methods. D-tests were conducted using clindamycin and erythromycin discs to detect inducible clindamycin resistance, while cefoxitin disc tests were utilized to ascertain methicillin resistance. Data entry was executed using Epi-Data version 4.6, and subsequent analysis was performed utilizing SPSS version 25. Bivariable and multivariable logistic regression analyses were employed to identify associated factors. An adjusted odds ratio at a 95% confidence interval with a P-value of < 0.05 was considered statistically significant.

RESULTS

The overall nasopharyngeal carriage rate of Gram-positive bacteria was 296/424 (69.8%, 95% CI: 65.3-74.0). Staphylococcus aureus was the most prevalent 122/424 (28.8%), followed by Streptococcus pneumoniae 92/424 (21.7%). Methicillin resistance was observed in 19/122 (15.6%) of S. aureus and 3/60 (5%) of coagulase-negative staphylococcus (CoNS) species. Inducible clindamycin resistance was 10/122 (8.2%) in S. aureus and 4/53 (7.5%) in coagulase-negative staphylococcus species. Multidrug resistance was found in 146/296 (49.3%, 95% CI: 43.6-55.0) of the isolates. Associated factors with a bacterial carriage were large family size (AOR = 3.061, 95% CI: 1.595-5.874, P = 0.001), having siblings under five years old (AOR = 1.991, 95% CI: 1.196-3.313, P = 0.008), indoor cooking (AOR = 2.195, 95% CI: 1.275-3.778, P = 0.005), an illiterate mother (AOR = 3.639, 95% CI: 1.691-7.829, P = 0.001), and hospital visits (AOR = 2.690, 95% CI: 1.405-5.151, P = 0.003).

CONCLUSION

The study found a high nasopharyngeal carriage of Gram-positive bacteria in outpatient children, including notable levels of methicillin-resistant S. aureus and multi-drug-resistant isolates. Clindamycin, rifampin, and erythromycin were the most effective antimicrobials for the tested isolates. Factors contributing to bacterial carriage include visits to healthcare facilities, larger family sizes, having younger siblings, maternal illiteracy, and indoor cooking. This emphasizes the need for methicillin-resistant S. aureus surveillance in pediatric outpatient settings and community health education, especially for children's guardians. Additionally, improving household ventilation by separating kitchens from sleeping areas and regular screening of younger siblings in healthcare environments were recommended to reduce bacterial transmission within family members. The study also called for studies with advanced procedures like minimum inhibitory concentration testing and molecular characterization to better comprehend the resistance patterns and genes in circulating bacteria.

Application of Transthoracic Echocardiography for Cardiac Safety Evaluation in the Clinical Development Process of Vaccines Against Streptococcus pyogenes

Superficial infections with Streptococcus pyogenes (Strep A), pharyngitis and impetigo can induce acute rheumatic fever, an autoimmune sequela manifesting mostly with arthritis and rheumatic carditis. Valvular heart damage can persist or advance following repeated episodes of acute rheumatic fever, causing rheumatic heart disease. Acute rheumatic fever and rheumatic heart disease disproportionately affect children and young adults in developing countries and disadvantaged communities in developed countries. People living with rheumatic heart disease are at risk of experiencing potentially fatal complications such as heart failure, bacterial endocarditis or stroke. Transthoracic echocardiography plays a central role in diagnosing both rheumatic carditis and rheumatic heart disease. Despite the obvious medical need, no licensed Strep A vaccines are currently available, as their clinical development process faces several challenges, including concerns for cardiac safety. However, the development of Strep A vaccines has been recently relaunched by many vaccine developers. In this context, a reliable and consistent safety evaluation of Strep A vaccine candidates, including the use of transthoracic echocardiography for detecting cardiac adverse events, could greatly contribute to developing a safe and efficacious product in the near future. Here, we propose a framework for the consistent use of transthoracic echocardiography to proactively detect cardiac safety events in clinical trials of Strep A vaccine candidates.

A Longitudinal Study of Group A Streptococcal Colonization and Pharyngitis in US Children

BACKGROUND

Group A streptococci (GAS) are a major cause of pharyngitis in children. Recently, there were severe GAS outbreaks. The aims of this study were to assess pharyngeal colonization prevalence in healthy children, to assess different diagnostic definitions for GAS pharyngitis and to estimate incidence rates for these infections.

METHODS

A 2-year longitudinal study was conducted in healthy children in the United States. Pharyngeal swabs were cultured every 3 months for GAS colonization. Serum antistreptolysin O, antideoxyribonuclease B (DNaseB) and antistreptococcal C5a peptidase (SCP) antibody titers were assessed at baseline. When participants developed a sore throat, pharyngeal swabs were collected for rapid antigen detection test (RADT) and culture, and antibody titers were determined in serum samples. A range of case definitions were used for GAS pharyngitis.

RESULTS

A total of 422 children 3-12 years old were enrolled (140, 141 and 141 were 3-5, 6-9 and 10-12 years of age, respectively). The overall prevalence of GAS colonization during the study was 48%. Baseline antistreptolysin O, anti-DNaseB and anti-SCP antibody titers were higher for children older than 5 years. The incidence of GAS pharyngitis per 100 person-years was 15.9 for RADT/culture-proven and 4.6 for serologically confirmed pharyngitis.

CONCLUSIONS

GAS throat colonization and pharyngitis were frequent in children 3-12 years old. The case definition employed impacted the measured incidence of GAS pharyngitis, with higher rates detected using RADT/culture-based definitions. These data suggest that case definition is important and that young children are exposed to GAS, which may inform plans for vaccine development and implementation.

Role of serotype and virulence determinants of Streptococcus pyogenes biofilm bacteria in internalization and persistence in epithelial cells in vitro

Streptococcus pyogenes causes a multitude of local and systemic infections, the most common being pharyngitis in children. Recurrent pharyngeal infections are common and are thought to be due to the re-emergence of intracellular GAS upon completion of antibiotic treatment. The role of colonizing biofilm bacteria in this process is not fully clear. Here, live respiratory epithelial cells were inoculated with broth-grown or biofilm bacteria of different M-types, as well as with isogenic mutants lacking common virulence factors. All M-types tested adhered to and were internalized into epithelial cells. Interestingly, internalization and persistence of planktonic bacteria varied significantly between strains, whereas biofilm bacteria were internalized in similar and higher numbers, and all strains persisted beyond 44 hours, showing a more homogenous phenotype. The M3 protein, but not the M1 or M5 proteins, was required for optimal uptake and persistence of both planktonic and biofilm bacteria inside cells. Moreover, the high expression of capsule and SLO inhibited cellular uptake and capsule expression was required for intracellular survival. Streptolysin S was required for optimal uptake and persistence of M3 planktonic bacteria, whereas SpeB improved intracellular survival of biofilm bacteria. Microscopy of internalized bacteria showed that planktonic bacteria were internalized in lower numbers as individual or small clumps of bacteria in the cytoplasm, whereas GAS biofilm bacteria displayed a pattern of perinuclear localization of bacterial aggregates that affected actin structure. Using inhibitors targeting cellular uptake pathways, we confirmed that planktonic GAS mainly uses a clathrin-mediated uptake pathway that also required actin and dynamin. Clathrin was not involved in biofilm internalization, but internalization required actin rearrangement and PI3 kinase activity, possibly suggesting macropinocytosis. Together these results provide a better understanding of the potential mechanisms of uptake and survival of various phenotypes of GAS bacteria relevant for colonization and recurrent infection.

The effects of air pollutants exposure on the transmission and severity of invasive infection caused by an opportunistic pathogen Streptococcus pyogenes

Currently, urbanization is associated with an increase in air pollutants that contribute to invasive pathogen infections by altering the host's innate immunity and antimicrobial resistance capability. Streptococcus pyogenes, also known as Group A Streptococcus (GAS), is a gram-positive opportunistic pathogen that causes a wide range of diseases, especially in children and immunosuppressed individuals. Diesel exhaust particle (DEP), a significant constituent of particulate matter (PM), are considered a prominent risk factor for respiratory illness and circulatory diseases worldwide. Several clinical and epidemiological studies have identified a close association between PM and the prevalence of viral and bacterial infections. This study investigated the role of DEP exposure in increasing pulmonary and blood bacterial counts and mortality during GAS M1 strain infection in mice. Thus, we characterized the upregulation of reactive oxygen species production and disruption of tight junctions in the A549 lung epithelial cell line due to DEP exposure, leading to the upregulation of GAS adhesion and invasion. Furthermore, DEP exposure altered the leukocyte components of infiltrated cells in bronchoalveolar lavage fluid, as determined by Diff-Quik staining. The results highlighted the DEP-related macrophage dysfunction, neutrophil impairment, and imbalance in pro-inflammatory cytokine production via the toll-like receptor 4/mitogen-activated protein kinase signaling axis. Notably, the tolerance of the GAS biofilms toward potent antibiotics and bacterial resistance against environmental stresses was also significantly enhanced by DEP. This study aimed to provide a better understanding of the physiological and molecular interactions between exposure to invasive air pollutants and susceptibility to invasive GAS infections.

A Review of Streptococcus pyogenes: Public Health Risk Factors, Prevention and Control

Streptococcus pyogenes, (colloquially named "group A streptococcus" (GAS)), is a pathogen of public health significance, infecting 18.1 million people worldwide and resulting in 500,000 deaths each year. This review identified published articles on the risk factors and public health prevention and control strategies for mitigating GAS diseases. The pathogen causing GAS diseases is commonly transmitted via respiratory droplets, touching skin sores caused by GAS or through contact with contaminated material or equipment. Foodborne transmission is also possible, although there is need for further research to quantify this route of infection. It was found that GAS diseases are highly prevalent in developing countries, and among indigenous populations and low socioeconomic areas in developed countries. Children, the immunocompromised and the elderly are at the greatest risk of S. pyogenes infections and the associated sequelae, with transmission rates being higher in schools, kindergartens, hospitals and residential care homes. This was attributed to overcrowding and the higher level of social contact in these settings. Prevention and control measures should target the improvement of living conditions, and personal and hand hygiene. Adherence to infection prevention and control practices should be emphasized in high-risk settings. Resource distribution by governments, especially in developed countries, should also be considered.

Streptococcus pyogenes Is Associated with Idiopathic Cutaneous Ulcers in Children on a Yaws-Endemic Island

Exudative cutaneous ulcers (CU) in yaws-endemic areas are associated with Treponema pallidum subsp. pertenue (TP) and Haemophilus ducreyi (HD), but one-third of CU cases are idiopathic (IU). Using mass drug administration (MDA) of azithromycin, a yaws eradication campaign on Lihir Island in Papua New Guinea reduced but failed to eradicate yaws; IU rates remained constant throughout the campaign. To identify potential etiologies of IU, we obtained swabs of CU lesions (n = 279) and of the skin of asymptomatic controls (AC; n = 233) from the Lihir Island cohort and characterized their microbiomes using a metagenomics approach. CU bacterial communities were less diverse than those of the AC. Using real-time multiplex PCR with pathogen-specific primers, we separated CU specimens into HD-positive (HD+), TP+, HD+TP+, and IU groups. Each CU subgroup formed a distinct bacterial community, defined by the species detected and/or the relative abundances of species within each group. Streptococcus pyogenes was the most abundant organism in IU (22.65%) and was enriched in IU compared to other ulcer groups. Follow-up samples (n = 31) were obtained from nonhealed ulcers; the average relative abundance of S. pyogenes was 30.11% in not improved ulcers and 0.88% in improved ulcers, suggesting that S. pyogenes in the not improved ulcers may be azithromycin resistant. Catonella morbi was enriched in IU that lacked S. pyogenes As some S. pyogenes and TP strains are macrolide resistant, penicillin may be the drug of choice for CU azithromycin treatment failures. Our study will aid in the design of diagnostic tests and selective therapies for CU.IMPORTANCE Cutaneous ulcers (CU) affect approximately 100,000 children in the tropics each year. While two-thirds of CU are caused by Treponema pallidum subspecies pertenue and Haemophilus ducreyi, the cause(s) of the remaining one-third is unknown. Given the failure of mass drug administration of azithromycin to eradicate CU, the World Health Organization recently proposed an integrated disease management strategy to control CU. Success of this strategy requires determining the unknown cause(s) of CU. By using 16S rRNA gene sequencing of swabs obtained from CU and the skin of asymptomatic children, we identified another possible cause of skin ulcers, Streptococcus pyogenes Although S. pyogenes is known to cause impetigo and cellulitis, this is the first report implicating the organism as a causal agent of CU. Inclusion of S. pyogenes into the integrated disease management plan will improve diagnostic testing and treatment of this painful and debilitating disease of children and strengthen elimination efforts.

Survival of Group A Streptococcus (GAS) is Enhanced Under Desiccated Culture Conditions

Streptococcus pyogenes or Group A Streptococcus (GAS) infections are the leading cause of bacterial tonsillopharyngitis. The bacterium can survive and persist within the human host for a long time as it is observed in up to 40% of the population who are considered as carriers. Recurrent tonsillopharyngitis is a particular problem in children which is caused either by relapses due to failed bacterial clearance or by reinfection. A prolonged survival in tonsillar crypts or on inanimate surfaces might be sources for reinfection. We therefore examined 64 clinical GAS isolates from children with tonsillopharyngitis for their long-term survival under either liquid or desiccated culture conditions. After 6 weeks, the overall GAS survival rate was 400-fold increased under desiccated culture conditions compared to liquid culture conditions, but varied depending on the emm-type between 20-fold (emm4) and 14000-fold (emm3). The survival rates of isolates from emm75 were significantly lower which is probably due to their production of hydrogen peroxide up to fatal doses. No hydrogen peroxide production could be detected for other emm-types. Furthermore, 11 isolates from patients with recurrent tonsillopharyngitis were compared to isolates of the same emm-type from patients with single episodes of tonsillopharyngitis. A significant elevated pH value and an increased survival rate for isolates from patients with recurrent infections were observed. In conclusion, significant differences in long-term survival of different GAS isolates as well as survival under desiccated culture conditions might contribute to both failed bacterial clearance and reinfection in patients with recurrent tonsillopharyngitis.

Group A Streptococcus infections in children: from virulence to clinical management

PURPOSE OF REVIEW

Recent findings have open new perspectives on group A Streptococcus (GAS) virulence understanding with special focus on the carrier stage and new hopes for an efficient vaccine against this important pathogen.

RECENT FINDINGS

Understanding of carriage state, transmission and role of virulence factors in invasive infections have been recently active research fields questioning the link between carriage and infections and highlighting the potential to prevent invasive diseases. New roles for already well known virulence factors, such as Streptolysin O, M protein or NAD(+)-glycohydrolase have been discovered. Immunological studies have also shown diversity in both clinical and immunological responses toward various GAS antigens raising questions, and hopes, for the development of an efficient global vaccine candidate.

SUMMARY

A greater understanding of GAS virulence strategies, and their associated clinical manifestations, may be obtained by shifting our research scope toward virulence determinant interactions and cooperation rather than focusing on individual virulence factor or specific strain characterization only.

Streptococcal pharyngitis and rheumatic heart disease: the superantigen hypothesis revisited

Streptococcus pyogenes is a human-specific and globally prominent bacterial pathogen that despite causing numerous human infections, this bacterium is normally found in an asymptomatic carrier state. This review provides an overview of both bacterial and human factors that likely play an important role in nasopharyngeal colonization and pharyngitis, as well as the development of acute rheumatic fever and rheumatic heart disease. Here we highlight a recently described role for bacterial superantigens in promoting acute nasopharyngeal infection, and discuss how these immune system activating toxins could be crucial to initiate the autoimmune process in rheumatic heart disease.

Management of children with persistent group A streptococcal carriage

INTRODUCTION

Chronic GAS carrier state is best defined as the prolonged presence of group A β-haemolytic Streptococcus (GAS) in the pharynx without evidence of infection or inflammation. Chronic GAS carriers have a low risk of immune mediated complications. Persistent pharyngeal carriage often raises management issues. In this study, we review the evidence on the management of persistent GAS carriage in children and propose a management algorithm. Areas covered: Chronic GAS pharyngeal carriage is quite common affecting 10-20% of school-aged children. Pathogenesis of carriage has been related to the pharynx microflora and to special properties of GAS, but several aspects are yet to be elucidated. Management greatly depends on whether the individual child belongs to a 'high-risk' group and might benefit from eradication regimens or not, when observation-only and reassurance are enough. Penicillin plus rifampin and clindamycin monotherapy have been recommended for eradication; limited evidence of effectiveness of azithromycin has been reported. Surgical intervention is not indicated. Expert commentary: GAS infection is a common reason for antibiotic use and abuse in children and asymptomatic carriers constitute the major reservoir of GAS in the community. Several aspects are yet to be elucidated and well-designed studies are needed for firm conclusions to be drawn.

Local Th17/IgA immunity correlate with protection against intranasal infection with Streptococcus pyogenes

Streptococcus pyogenes (group A streptococcus, GAS) is responsible for a wide array of infections. Respiratory transmission via droplets is the most common mode of transmission but it may also infect the host via other routes such as lesions in the skin. To advance the development of a future vaccine against GAS, it is therefore important to investigate how protective immunity is related to the route of vaccine administration. To explore this, we examined whether a parenterally administered anti-GAS vaccine could protect against an intranasal GAS infection or if this would require locally primed immunity. We foundd that a parenteral CAF01 adjuvanted GAS vaccine offered no protection against intranasal infection despite inducing strong systemic Th1/Th17/IgG immunity that efficiently protected against an intraperitoneal GAS infection. However, the same vaccine administered via the intranasal route was able to induce protection against repeated intranasal GAS infections in a murine challenge model. The lack of intranasal protection induced by the parenteral vaccine correlated with a reduced mucosal recall response at the site of infection. Taken together, our results demonstrate that locally primed immunity is important for the defense against intranasal infection with Streptococcus pyogenes.