Whole-genome sequencing reveals clonal expansion of multiresistant Staphylococcus haemolyticus in European hospitals

Jorunn Pauline Cavanagh, Erik Hjerde, Matthew T G Holden, Tim Kahlke, Claus Klingenberg, Trond Flægstad, Julian Parkhill, Stephen D Bentley, Johanna U Ericson Sollid

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31 Citations (Scopus)


Objectives Staphylococcus haemolyticus is an emerging cause of nosocomial infections, primarily affecting immunocompromised patients. A comparative genomic analysis was performed on clinical S. haemolyticus isolates to investigate their genetic relationship and explore the coding sequences with respect to antimicrobial resistance determinants and putative hospital adaptation.

Methods Whole-genome sequencing was performed on 134 isolates of S. haemolyticus from geographically diverse origins (Belgium, 2; Germany, 10; Japan, 13; Norway, 54; Spain, 2; Switzerland, 43; UK, 9; USA, 1). Each genome was individually assembled. Protein coding sequences (CDSs) were predicted and homologous genes were categorized into three types: Type I, core genes, homologues present in all strains; Type II, unique core genes, homologues shared by only a subgroup of strains; and Type III, unique genes, strain-specific CDSs. The phylogenetic relationship between the isolates was built from variable sites in the form of single nucleotide polymorphisms (SNPs) in the core genome and used to construct a maximum likelihood phylogeny.

Results SNPs in the genome core regions divided the isolates into one major group of 126 isolates and one minor group of isolates with highly diverse genomes. The major group was further subdivided into seven clades (A–G), of which four (A–D) encompassed isolates only from Europe. Antimicrobial multiresistance was observed in 77.7% of the collection. High levels of homologous recombination were detected in genes involved in adherence, staphylococcal host adaptation and bacterial cell communication.

Conclusions The presence of several successful and highly resistant clones underlines the adaptive potential of this opportunistic pathogen.
Original languageEnglish
Pages (from-to)2920-2927
JournalJournal of Antimicrobial Chemotherapy
Issue number11
Early online date17 Jul 2014
Publication statusPublished - 11 Nov 2014


  • Staphylococci
  • SCCmec
  • Molecular epidemiology
  • Multidrug resistance
  • Bacterial genomics


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