Original Article
Increase of emm1 isolates among group A Streptococcus strains causing scarlet fever in Shanghai, China

https://doi.org/10.1016/j.ijid.2020.06.053Get rights and content
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Highlights

  • Remarkable increase of emm1 proportion in GAS population.

  • Continuous data of ongoing scarlet fever outbreaks in China.

  • Average GAS carriage rate of 7.6% in school-aged children.

  • Characteristic mobile genetic elements harboured by Chinese emm1 isolates.

Abstract

Objective

Scarlet fever epidemics caused by group A Streptococcus (GAS) have been ongoing in China since 2011. However, limited data are available on the dynamic molecular characterizations of the epidemic strains.

Method

Epidemiological data of scarlet fever in Shanghai were obtained from the National Notifiable Infectious Disease Surveillance System. Throat swabs of patients with scarlet fever and asymptomatic school-age children were cultured. Illumina sequencing was performed on 39emm1 isolates.

Results

The annual incidence of scarlet fever was 7.5–19.4/100,000 persons in Shanghai during 2011–2015, with an average GAS carriage rate being 7.6% in school-age children. The proportion ofemm1 GAS strains increased from 3.8% in 2011 to 48.6% in 2014; they harbored a superantigen profile similar to emm12 isolates, except for the speA gene. Two predominant clones, SH001-emm12, and SH002-emm1, circulated in 66.9% of scarlet fever cases and 44.8% of carriers. Genomic analysis showed emm1 isolates throughout China constituted distinct clades, enriched by the presence of mobile genetic elements carrying the multidrug-resistant determinants ermB and tetM and virulence genes speA, speC, and spd1.

Conclusion

A significant increase in the proportion ofemm1 strains occurred in the GAS population, causing scarlet fever in China. Ongoing surveillance is warranted to monitor the dynamic changes of GAS clones.

Keywords

Scarlet fever
emm1
Group A Streptococcus
Antibiotic resistance
Pulse-field gel electrophoresis (PFGE)
Whole-genome sequencing
Genomic epidemiology

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1

These authors contributed equally to this article.