title: Identification of genetic variation exclusive to specific lineages associated with Staphylococcus aureus bacteraemia.
abstract: BACKGROUND
  Meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia cases have declined since 2003, and have mostly been due to two epidemic (E) strains, E15 (multi-locus sequence type clonal complex CC22) and E16 (CC30). By contrast, the incidence of meticillin-susceptible S. aureus (MSSA) bacteraemia has remained largely unchanged and our understanding of these isolates has remained poor.
  
  
  OBJECTIVE
  To investigate the distribution and nucleotide sequence of heterogeneous regions between successful lineages using the 2009 British Society for Antimicrobial Chemotherapy (BSAC) Bacteraemia Resistance Surveillance Programme collection of S. aureus.
  
  
  METHODS
  S. aureus isolates (N = 202) comprised of 103 MRSA and 99 MSSA isolates were analysed using fluorescent amplified fragment length polymorphism (FAFLP) to detect nucleotide variations due to lineage-specific sequence motifs as well as differences in the distribution of mobile genetic elements between lineages.
  
  
  RESULTS
  E15 and E16 MRSA strains comprised 79% and 6% of the collection in 2009 respectively. Six lineages, including CC22 and CC30, were associated with MRSA bacteraemia in the UK and Ireland. MSSA isolates were more diverse with 19 different lineages detected. FAFLP revealed lineage-specific sequence variations in loci encoding factors such as proteases or factors involved in haem biosynthesis, both of which may affect the success of major S. aureus lineages. Proteins encoded on certain mobile genetic elements or involved in cobalamin biosynthesis were found to be exclusive to CC8, CC22, or CC30.
  
  
  CONCLUSIONS
  Overall, the genetic diversity among regions of the core genome and mobile genetic elements may alter antimicrobial resistance and the production of virulence or fitness factors that may be linked to strain success.
authors: Genomic Services and Development Unit, Microbiology Services Colindale, Public Health England, London, UK.
authors: D
authors: D
authors: Patel
authors: Microbiology Services Cambridge, Public Health England, Addenbrooke's Hospital, Cambridge, UK.
authors: M J
authors: MJ
authors: Ellington
authors: Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, Microbiology Services Colindale, Public Health England, London, UK.
authors: R
authors: R
authors: Hope
authors: Infection Sciences, North Bristol NHS Trust, Bristol, UK; British Society of Antimicrobial Chemotherapy, Birmingham, UK.
authors: R
authors: R
authors: Reynolds
authors: Genomic Services and Development Unit, Microbiology Services Colindale, Public Health England, London, UK.
authors: C
authors: C
authors: Arnold
authors: Genomic Services and Development Unit, Microbiology Services Colindale, Public Health England, London, UK. Electronic address: meeta.desai@phe.gov.uk.
authors: M
authors: M
authors: Desai
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D014644:Genetic Variation; D020071:Interspersed Repetitive Sequences; D007494:Ireland / Q000453:epidemiology; D017720:Molecular Epidemiology; D058889:Molecular Typing; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006113:United Kingdom / Q000453:epidemiology; D037521:Virulence Factors / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D037521:Virulence Factors
keywords: Bacteraemia; Genetic diversity; Lineage; Staphylococcus aureus