title: Current views of haemolytic streptococcal pathogenesis.
abstract: OBJECTIVE
  Increasing disease caused by beta-haemolytic streptococci indicates the need for improved understanding of pathogenesis.
  
  
  RESULTS
  Streptococcus pyogenes, or group A Streptococcus (GAS), causes significant disease worldwide. The closely related Streptococcus dysgalactiae subspecies equisimilis (SDSE) is increasingly recognized as causing a similar disease spectrum. Whole-genome sequencing applied to the study of outbreaks may reveal factors that contribute to pathogenesis and changes in epidemiology. The role of quorum sensing in biofilm formation, and interspecies communication with other streptococci, is discussed. GAS has evolved multiple mechanisms to evade the humoral arm of innate immunity, including complement, which is well known in protecting the host from bacteria, and the coagulation-fibrinolytic system, which is increasingly recognized as an innate immune effector.
  
  
  CONCLUSIONS
  Molecular biology has enhanced our understanding of the intricate balance of host-pathogen interactions that result in clearance or establishment of invasive streptococcal infection. Although the skin and oropharynx remain the usual ecological niche of GAS and SDSE, occasionally the bacteria find themselves within deeper tissues and blood. Recent research has armed us with better knowledge of bacterial adaptations to this alternative environment. However, the challenge is to translate this knowledge into clinical practice, through the development of novel therapeutic options and ultimately a vaccine against GAS.
authors.affiliation: aSection of Infectious Diseases and Immunity, Imperial College London, Hammersmith Campus bDepartment of Haematology, Imperial College Healthcare NHS Trust, Hammersmith Hospital, London, UK.
authors.forename: Lionel K K
authors.initials: LK
authors.lastname: Tan
authors.forename: Lydia R J
authors.initials: LR
authors.lastname: Eccersley
authors.forename: Shiranee
authors.initials: S
authors.lastname: Sriskandan
mesh_terms: D016680:Genome, Bacterial / Q000502:physiology; D054884:Host-Pathogen Interactions; D006801:Humans; D057131:Immune Evasion / Q000502:physiology; D008967:Molecular Biology; D012307:Risk Factors; D013290:Streptococcal Infections / Q000175:diagnosis / Q000382:microbiology / Q000503:physiopathology*; D013291:Streptococcus / Q000472:pathogenicity*