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Molecular Methods Enhance the Detection of Pyoderma-Related Streptococcus pyogenes and emm-Type Distribution in
Jennifer N Hall1,2,3, Edwin P Armitage4,5, Elina Senghore4
1Division of Clinical Medicine and National Institute for Health and Care Research Sheffield Biomedical Research Centre, School of Medicine and Population Health, University of Sheffield, Sheffield, United Kingdom.
Insights
Bacterial culture underestimates Streptococcus pyogenes in skin infections, especially with Staphylococcus aureus. Molecular methods like qPCR are crucial for accurate detection in rheumatic heart disease-endemic areas.
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.
Background:
Streptococcus pyogenes-related skin infections are increasingly implicated in the development of rheumatic heart disease (RHD) in lower-resource settings, where they are often associated with scabies. The true prevalence of S pyogenes-related pyoderma may be underestimated by bacterial culture.
Methods:
A multiplex quantitative polymerase chain reaction (qPCR) assay for S pyogenes, Staphylococcus aureus, and Sarcoptes scabiei was applied to 250 pyoderma swabs from a cross-sectional study of children aged <5 years in The Gambia. Direct PCR-based emm-typing was used to supplement previous whole genome sequencing (WGS) of cultured isolates.
Results:
Pyoderma lesions with S pyogenes increased from 51% (127/250) using culture to 80% (199/250) with qPCR. Compared to qPCR, the sensitivity of culture was 95.4% for S pyogenes (95% confidence interval {CI}, 77.2%-99.9%) in samples with S pyogenes alone (22/250 [9%]), but 59.9% (95% CI, 52.3%-67.2%) for samples with S aureus coinfection (177/250 [71%]). Direct PCR-based emm-typing was successful in 50% (46/92) of cases, identifying 27 emm-types, including 6 not identified by WGS (total 52 emm-types).
Conclusions:
Bacterial culture significantly underestimates the burden of S pyogenes in pyoderma, particularly with S aureus coinfection. Molecular methods should be used to enhance the detection of S pyogenes in surveillance studies and clinical trials of preventive measures in RHD-endemic settings.
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