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Updated: May 19, 2026
04:25
Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
Superantigen gene complement of Streptococcus pyogenes--relationship with other typing methods and short-term
A Friães1, F R Pinto, C Silva-Costa
1Instituto de Microbiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av Prof Egas Moniz, 1649-028 Lisboa, Portugal.
Summary
Superantigen (SAg) gene profiling offers a valuable tool for Group A Streptococcus (GAS) typing. This study developed a robust polymerase chain reaction (PCR) method to accurately identify SAg genes, aiding molecular epidemiology.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Superantigen (SAg) gene profiling is a common typing method for Group A Streptococcus (GAS).
- Inconsistent nomenclature and primer diversity have caused conflicting results in previous studies.
- A need exists for a standardized and efficient method for SAg gene profiling in GAS.
Purpose of the Study:
- To develop a polymerase chain reaction (PCR) method for efficient amplification of all known superantigen (SAg) gene allelic variants in Group A Streptococcus (GAS).
- To evaluate the congruence of the developed PCR methodology with other standard molecular typing techniques.
- To investigate the distribution and associations of SAg genes within a large collection of clinical GAS isolates.
Main Methods:
- Developed and utilized two multiplex PCR reactions to screen 480 clinical GAS isolates for 11 known SAg genes and two additional exotoxin genes (speB, speF).
- Compared the SAg gene profiles with other molecular typing methods, including emm typing and pulsed-field gel electrophoresis (PFGE).
- Employed Southern blot hybridization to confirm the absence of specific chromosomally encoded genes (speG, smeZ).
Main Results:
- Successfully amplified all known allelic variants of SAg genes using the developed multiplex PCR assays.
- Characterized four naturally occurring deletions in speB, speF, and rgg genes, with two found in invasive isolates.
- Observed positive associations between SAg genes, SAg profiles, emm types, and PFGE clusters, indicating SAg profile diversification.
Conclusions:
- The developed PCR method provides an efficient and accurate way to profile SAg genes in GAS.
- SAg gene profiles diversify more rapidly than emm types or MLST sequence types, making them a useful complement for GAS molecular epidemiology.
- The observed associations suggest short-term stability of SAg gene profiles within prevalent GAS genetic lineages.
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