Identification of a chimeric emm gene and novel emm pattern in currently circulating strains of emm4 Group A Streptococcus

Microb Genom. 2018 Nov;4(11):e000235. doi: 10.1099/mgen.0.000235. Epub 2018 Nov 9.


Group A Streptococcus (GAS) is classified on the basis of the sequence of the gene encoding the M protein (emm) and the patterns into which emm types are grouped. We discovered a novel emm pattern in emm4 GAS, historically considered pattern E, arising from a fusion event between emm and the adjacent enn gene. We identified the emm-enn fusion event in 51 out of 52 emm4 GAS strains isolated by national surveillance in 2015. GAS isolates with an emm-enn fusion event completely replaced pattern E emm4 strains over a 4-year span in Houston (2013-2017). The novel emm-enn gene fusion and new emm pattern has potential vaccine implications.

Keywords: chimeric M protein; emm pattern; emm/enn gene fusion event; group A Streptococcus.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Antigens, Bacterial / genetics*
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Proteins / genetics
  • Carrier Proteins / genetics*
  • Gene Fusion*
  • Humans
  • Streptococcus pyogenes / genetics*
  • Streptococcus pyogenes / isolation & purification


  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • Enn protein, Streptococcus pyogenes
  • streptococcal M protein