Molecular Methods Enhance the Detection of Pyoderma-Related Streptococcus pyogenes and emm-Type Distribution in...

Area of Science:

• Microbiology
• Infectious Diseases
• Public Health

Background:

• Streptococcus pyogenes (S. pyogenes) skin infections are linked to rheumatic heart disease (RHD) in low-resource settings.
• These infections are often co-occurring with scabies.
• Bacterial culture may underestimate the true prevalence of S. pyogenes in pyoderma.

Purpose of the Study:

• To compare the diagnostic accuracy of bacterial culture and quantitative polymerase chain reaction (qPCR) for S. pyogenes in pyoderma.
• To assess the prevalence of S. pyogenes and Staphylococcus aureus coinfection in pediatric pyoderma.
• To evaluate direct PCR-based emm-typing for S. pyogenes strain characterization.

Main Methods:

• A multiplex qPCR assay was used to detect S. pyogenes, S. aureus, and Sarcoptes scabiei in 250 pyoderma swabs from children under 5 in The Gambia.
• Direct PCR-based emm-typing was performed on positive samples.
• Results were compared to previous bacterial culture and whole genome sequencing (WGS) data.

Main Results:

• qPCR detected S. pyogenes in 80% of lesions, significantly higher than the 51% detected by culture.
• Culture sensitivity for S. pyogenes was reduced in cases of S. aureus coinfection (59.9%) compared to S. pyogenes alone (95.4%).
• Direct PCR-based emm-typing identified 52 S. pyogenes emm-types, including 6 missed by WGS.

Conclusions:

• Bacterial culture significantly underestimates S. pyogenes burden in pyoderma, particularly when S. aureus is present.
• Molecular methods are essential for accurate S. pyogenes detection in RHD-endemic regions.
• Enhanced detection is vital for surveillance and evaluating interventions for RHD prevention.