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Change during an 8-Year Period in Streptococcus Pyogenes emm Types in Pharyngeal Isolates from Children with
Toshinari Okabe1, Yoshihiko Norose2, Masatoshi Hida1
1Department of Pediatrics, Nippon Medical School Tama Nagayama Hospital.
Insights
The predominant Streptococcus pyogenes (group A streptococcus) emm type shifted from emm12 to emm1 over eight years. This study also identified three group G streptococcus strains with M-like protein genes.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Streptococcus pyogenes (group A streptococcus, GAS) is a common pediatric bacterial pathogen causing diverse infections.
- GAS pathogenicity is linked to its surface M protein, crucial for emm typing.
- Previous studies characterized GAS emm types in local pediatric noninvasive infections.
Purpose of the Study:
- To compare emm types of GAS strains isolated from children eight years after a prior study.
- To identify changes in predominant emm types and characterize co-circulating streptococcal species.
Main Methods:
- Pharyngeal swab specimens were collected from 23 pediatric patients (inpatients and outpatients) in 2016-2017.
- Polymerase chain reaction (PCR) was used to amplify genes encoding M proteins for emm typing.
Main Results:
- emm type analysis revealed emm1 as the predominant type (11/23 strains), a shift from the previous study's emm12.
- emm12 was identified in 4 of the 23 GAS strains.
- Three group G streptococcus (GGS) strains were detected, carrying M-like protein genes (stg245, stg6795, or stg840).
Conclusions:
- The dominant emm type among pediatric GAS isolates has changed from emm12 to emm1 over an eight-year period.
- The study identified GGS strains carrying specific M-like protein genes, highlighting potential cross-reactivity or co-infection.
- One GAS strain harbored stg485, a gene typically associated with GGS, indicating genetic exchange or misclassification.
Background:
Streptococcus pyogenes, or group A streptococcus (GAS), is one of the most common bacterial pathogens in children. GAS can cause such nonserious and noninvasive diseases as pharyngitis and skin infection, as well as serious, invasive diseases like streptococcal toxic shock syndrome. One factor that makes GAS pathogenic is the type-specific M protein on its cell surface. To identify emm types and their characteristics, we previously examined GAS strains isolated from children with noninvasive infections at our hospital. The present study was conducted 8 years later, for comparison.
Methods:
The 23 participants were inpatients and outpatients at Nippon Medical School Tama Nagayama Hospital during 2016 and 2017. A pharyngeal swab specimen was obtained from each child, and genes encoding M proteins were amplified by polymerase chain reaction.
Results:
emm type analysis identified emm1 in 11 of the 23 strains and emm12 in 4. Three group G streptococcus (GGS) strains carried M-like protein genes.
Conclusions:
The predominant emm type was emm12 in our previous report and emm1 in this study. This study also identified 3 GGS strains among the isolates, which carried either the stg245, stg6795, or stg840 M-like protein gene. One GAS strain carried stg485, a gene associated with GGS rather than GAS.
