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Published on: August 6, 2011

Molecular characterization of the 2011 Hong Kong scarlet fever outbreak

Herman Tse1, Jessie Y J Bao, Mark R Davies

  • 1Department of Microbiology, The University of Hong Kong, Hong Kong Special Administrative Region, China. htse@hkucc.hku.hk

The Journal of Infectious Diseases
|May 23, 2012
PubMed

Insights

The 2011 Hong Kong scarlet fever outbreak involved multidrug-resistant Streptococcus pyogenes emm12 strains. Mobile genetic elements, not covRS mutations, likely contributed to virulence, suggesting complex outbreak drivers.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Scarlet fever outbreaks pose public health challenges.
  • Streptococcus pyogenes emm12 strains were implicated in a 2011 Hong Kong outbreak.
  • Multiple antibiotic resistances were observed in outbreak isolates.

Purpose of the Study:

  • To investigate the genetic basis and contributing factors of the 2011 emm12 scarlet fever outbreak in Hong Kong.
  • To analyze the phylogenetic relationships of outbreak and non-outbreak strains.
  • To identify mobile genetic elements associated with virulence and resistance.

Main Methods:

  • Phylogenetic analysis of emm12 Streptococcus pyogenes isolates.
  • Whole-genome sequencing of representative isolates.
  • Diagnostic polymerase chain reaction assays.
  • Phenotypic characterization including adherence, neutrophil resistance, and murine models.

Main Results:

  • The 2011 outbreak was multiclonal, involving multiple emm12 lineages.
  • Two mobile genetic elements were identified: a conjugative element conferring antibiotic resistance and a prophage encoding virulence factors.
  • Virulence in outbreak strains was not linked to covRS mutations, unlike the M1T1 strain.
  • Increased adherence was observed in one isolate (HKU16).

Conclusions:

  • The multiclonal nature of the outbreak suggests diverse contributing factors.
  • Mobile genetic elements play a significant role in the emergence and virulence of Streptococcus pyogenes.
  • Environmental and host factors may also influence scarlet fever outbreaks.

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