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Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
Use of Host Response to Refine the Diagnosis of Group A Streptococcal Pharyngitis
Jinsheng Yu1, Eric Tycksen1, Wei Yang1
1Department of Genetics, Genome Technology Access Center at the McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Insights
Host response markers can differentiate between symptomatic group A Streptococcus (GAS) infections and asymptomatic colonization. This may lead to improved diagnosis of GAS pharyngitis and reduced antibiotic overuse.
Area of Science:
- Infectious Diseases
- Molecular Diagnostics
- Pediatric Health
Background:
- Current pharyngitis diagnostics fail to distinguish between symptomatic group A Streptococcus (GAS) infection and asymptomatic colonization.
- This leads to over-diagnosis and unnecessary antibiotic prescriptions.
Purpose of the Study:
- To assess if host response measures can differentiate symptomatic GAS from asymptomatic colonization.
- To explore novel diagnostic markers for GAS pharyngitis.
Main Methods:
- Enrolled children with pharyngitis (Centor scores 4-5) and asymptomatic controls.
- Performed throat cultures, molecular tests for GAS and viruses, and Epstein-Barr virus serology.
- Evaluated host response using white blood cell count (WBC), C-reactive protein (CRP), procalcitonin (PCT), and leukocyte RNA sequencing.
Main Results:
- 11 of 18 children had GAS pharyngitis; 5 asymptomatic controls were positive for GAS.
- WBC, CRP, and PCT levels were higher in symptomatic pharyngitis cases compared to asymptomatic controls.
- Gene expression profiles (CD177, TLR5) clearly distinguished symptomatic GAS from other groups, with CRP and PCT also showing high diagnostic accuracy.
Conclusions:
- Host inflammation markers and gene expression patterns can distinguish symptomatic GAS from asymptomatic colonization.
- These findings suggest potential for rapid molecular diagnostic approaches to improve GAS pharyngitis diagnosis.
- This could significantly reduce unnecessary antibiotic use in pediatric cases.
Background:
Current diagnostic tests for pharyngitis do not distinguish between symptomatic group A Streptococcus (GAS) infection and asymptomatic colonization, resulting in over-diagnosis and unnecessary use of antibiotics. We assessed whether measures of host response could make this distinction.
Methods:
We enrolled 18 children with pharyngitis having Centor scores of 4 or 5 and 21 controls without pharyngitis or other acute infections. Both groups had throat cultures, molecular tests for GAS and respiratory viruses and IgM serology for Epstein-Barr virus. Host response was evaluated with white blood cell count (WBC), C-reactive protein (CRP), procalcitonin (PCT), and sequencing of RNA from peripheral blood leukocytes.
Results:
Of 18 cases, 11 had GAS pharyngitis, 3 had adenovirus pharyngitis and 4 had other pharyngitis. Among asymptomatic controls, 5 were positive for GAS. WBC, CRP, and PCT were higher in subjects with pharyngitis compared to asymptomatic controls including those with GAS. Transcriptional profiles from children with symptomatic GAS were clearly distinct from those of children in all other groups. The levels of two genes, CD177 and TLR5 each individually accurately distinguished between symptomatic and asymptomatic GAS. Optimal diagnostic sensitivity and specificity were achieved by the combination of CRP and PCT, and by each of the two gene markers.
Conclusion:
In this exploratory study, we showed that traditional measures of inflammation and markers of host gene expression distinguish between symptomatic and asymptomatic GAS. These results point to future rapid molecular approaches for improving the diagnosis of GAS pharyngitis, that may help reduce unnecessary antibiotic use.
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