Detection of group a streptococcal pharyngitis by quantitative PCR

Area of Science:

• Microbiology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Group A Streptococcus (GAS) is a common cause of bacterial pharyngitis, particularly in school-aged children.
• Current diagnostic methods, including culture, are time-consuming (24-48 hours) and can be complicated by asymptomatic GAS carriage.
• Developing rapid and accurate diagnostic tools for GAS pharyngitis is crucial for timely treatment and infection control.

Purpose of the Study:

• To develop and evaluate a quantitative polymerase chain reaction (qPCR) assay for the detection of GAS in pharyngeal swabs.
• To assess the suitability of the developed qPCR assay for clinical diagnosis of GAS pharyngitis.

Main Methods:

• Pharyngeal swabs were collected from children and adults presenting with sore throat.
• Two candidate PCR assays targeting speB and spy1258 genes were developed into qPCR assays.
• qPCR results were compared against standard culture-based methods for GAS detection; emm-typing and McIsaac scores were also utilized.

Main Results:

• The speB qPCR assay demonstrated 100% sensitivity and 100% specificity compared to culture.
• The spy1258 qPCR assay showed 87% sensitivity and 100% specificity.
• GAS was identified in 18.9% of samples, exclusively in children (26%); nine emm types were identified, with emm 89, 3, and 28 being most prevalent.

Conclusions:

• The speB qPCR assay is a highly sensitive and specific tool for diagnosing GAS pharyngitis.
• This qPCR method shows promise for improving the clinical diagnosis and research of GAS infections.