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Detection of group A streptococcus in children with confirmed viral pharyngitis and antiviral host response
Lauri Ivaska1,2, Jussi Niemelä3,4, Kirsi Gröndahl-Yli-Hannuksela5
1Departments of Paediatrics and Adolescent Medicine, Turku University Hospital and University of Turku, Turku, Finland. lauri.ivaska@utu.fi.
Insights
Group A Streptococcus (GAS) was often found in children with viral pharyngitis, suggesting incidental throat carriage. Sensitive diagnostic methods increased GAS detection, highlighting the risk of overtreatment in pediatric cases.
Area of Science:
- Pediatric Infectious Diseases
- Microbiology
- Diagnostic Medicine
Background:
- The co-detection and clinical significance of Group A Streptococcus (GAS) and viral infections in pediatric pharyngitis are not well understood.
- Identifying a viral infection alongside an antiviral host response typically indicates a symptomatic viral illness.
Purpose of the Study:
- To investigate the detection rates of GAS using various diagnostic methods in children with pharyngitis, comparing those with and without confirmed viral infections.
- To assess the implications of GAS detection in the context of viral pharyngitis in pediatric patients.
Main Methods:
- A prospective observational study involving children aged 1-16 years presenting with febrile pharyngitis.
- Throat swabs and blood samples were collected for GAS testing (throat culture, rapid antigen detection tests, NAATs) and viral diagnostics (NAAT, serology).
- Confirmed viral infection was defined by positive viral tests and elevated MxA protein levels, indicating an antiviral host response.
Main Results:
- Of 48 children with available GAS testing, 30 (63%) had a confirmed viral infection, most commonly enteroviruses, adenoviruses, and rhinoviruses.
- GAS was detected in 17-43% of children with viral pharyngitis, depending on the diagnostic method used.
- Higher GAS detection rates were observed in children without confirmed viral infections (33-56%) compared to those with viral infections (13-43%).
Conclusions:
- Group A Streptococcus (GAS) is frequently detected in pediatric pharyngitis patients even when a viral infection is confirmed.
- The high detection rates of GAS, particularly with sensitive methods, in the presence of a viral host response suggest incidental throat carriage.
- These findings underscore the risk of misinterpreting incidental GAS pharyngeal carriage as a true infection in children with viral pharyngitis, potentially leading to unnecessary antibiotic treatment.
Abstract:
Our aim was to study the detection of group A streptococcus (GAS) with different diagnostic methods in paediatric pharyngitis patients with and without a confirmed viral infection. In this prospective observational study, throat swabs and blood samples were collected from children (age 1-16 years) presenting to the emergency department with febrile pharyngitis. A confirmed viral infection was defined as a positive virus diagnostic test (nucleic acid amplification test [NAAT] and/or serology) together with an antiviral immune response of the host demonstrated by elevated (≥ 175 µg/L) myxovirus resistance protein A (MxA) blood concentration. Testing for GAS was performed by a throat culture, by 2 rapid antigen detection tests (StrepTop and mariPOC) and by 2 NAATs (Simplexa and Illumigene). Altogether, 83 children were recruited of whom 48 had samples available for GAS testing. Confirmed viral infection was diagnosed in 30/48 (63%) children with febrile pharyngitis. Enteroviruses 11/30 (37%), adenoviruses 9/30 (30%) and rhinoviruses 9/30 (30%) were the most common viruses detected. GAS was detected by throat culture in 5/30 (17%) with and in 6/18 (33%) patients without a confirmed viral infection. Respectively, GAS was detected in 4/30 (13%) and 6/18 (33%) by StrepTop, 13/30 (43%) and 10/18 (56%) by mariPOC, 6/30 (20%) and 9/18 (50%) by Simplexa, and 5/30 (17%) and 6/18 (30%) patients by Illumigene.
Conclusion:
GAS was frequently detected also in paediatric pharyngitis patients with a confirmed viral infection. The presence of antiviral host response and increased GAS detection by sensitive methods suggest incidental throat carriage of GAS in viral pharyngitis.
What Is Known:
•The frequency and significance of GAS-virus co-detection are poorly characterised in children with pharyngitis. •Detection of a virus and the antiviral host response likely indicates symptomatic infection.
What Is New:
•Group A streptococcus (GAS) was detected in 17-43% of the children with confirmed viral pharyngitis depending on the GAS diagnostic method. •Our results emphasize the risk of detecting and treating incidental pharyngeal carriage of GAS in children with viral pharyngitis.
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