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Published on: July 11, 2016
emm typing of invasive T28 group A streptococci, 1995-2004, Finland
Tuula Siljander1, Maija Toropainen1, Anna Muotiala1
1Hospital Bacteria Laboratory, Department of Bacterial and Inflammatory Diseases, National Public Health Institute, Mannerheimintie 166, FIN-00300, Helsinki, Finland.
Abstract:
A total of 985 group A streptococcus (GAS) bacteraemia isolates collected in Finland during 1995-2004 were T-serotyped, and of these, 336 isolates of serotype T28 were subjected to further emm typing. The total number of isolates referred per year showed an increase within the study period, from 43 in 1995 to 130 in 2004. The annual incidence of invasive GAS (iGAS) bacteraemia showed a general increase during the study period, from 1.1 to 2.5 per 100 000 population. Serotype T28 remained among the most common serotypes, in addition to serotypes TB3264 and T1. The serotype T28 isolates were found to be distributed across six distinct emm types: emm28, emm77, emm53 (including subtypes 53.2 and 53.4), emm87, emm2 and emm4. The serotype distribution and the emm type distribution of serotype T28 fluctuated over time. Within the study period, the proportion of T28/emm28 isolates became the most prominent. During periods of low emm28 incidence, emm types 77 and 53 seemed to show a resurgence. emm typing revealed T28 isolates to be a genetically heterogeneous group harbouring a variety of distinct M proteins. This study confirms that T serotyping alone is not a sufficient method for epidemiological surveillance of iGAS.
Insights
Group A Streptococcus (GAS) bacteraemia cases increased from 1995-2004. T serotyping alone is insufficient for tracking invasive GAS (iGAS) due to genetic diversity within serotypes like T28.
Area of Science:
- Microbiology
- Epidemiology
- Infectious Diseases
Background:
- Group A Streptococcus (GAS) is a significant human pathogen.
- Invasive GAS (iGAS) infections, such as bacteraemia, pose a public health concern.
- Accurate epidemiological surveillance is crucial for understanding and controlling iGAS outbreaks.
Purpose of the Study:
- To investigate the genetic diversity of Group A Streptococcus (GAS) serotype T28 isolates.
- To evaluate the effectiveness of T serotyping versus emm typing for epidemiological surveillance of iGAS.
- To analyze trends in GAS bacteraemia incidence and serotype distribution in Finland.
Main Methods:
- Collected 985 GAS bacteraemia isolates in Finland (1995-2004).
- Performed T-serotyping on all isolates.
- Conducted emm typing on 336 T28 serotype isolates.
- Analyzed temporal trends in incidence and serotype/emm type distribution.
Main Results:
- GAS bacteraemia incidence increased from 1.1 to 2.5 per 100,000 population.
- Serotype T28 isolates were genetically diverse, belonging to six distinct emm types (emm28, emm77, emm53, emm87, emm2, emm4).
- The proportion of T28/emm28 isolates increased over time, with emm77 and emm53 showing resurgence during low emm28 periods.
- T serotyping alone was insufficient for detailed epidemiological surveillance.
Conclusions:
- emm typing provides a more detailed genetic resolution than T serotyping for GAS surveillance.
- Serotype T28 represents a genetically heterogeneous group of GAS.
- Epidemiological surveillance of iGAS requires methods that capture genetic diversity, such as emm typing.
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