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Comparative genotypic and phenotypic characterisation of methicillin-resistant Staphylococcus aureus ST398 isolated

Dorota M Jamrozy1, Mark D Fielder, Patrick Butaye

  • 1Department of Bacteriology, Animal Health and Veterinary Laboratories Agency, New Haw, United Kingdom. d.jamrozy@vla.defra.gsi.gov.uk

Plos One
|July 14, 2012
PubMed

Insights

Methicillin-resistant Staphylococcus aureus ST398 (MRSA ST398) has low virulence genes but high antimicrobial resistance. This successful lineage shows a unique genetic background, lacking specific virulence markers despite widespread prevalence in livestock.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Methicillin-resistant Staphylococcus aureus sequence type 398 (MRSA ST398) is prevalent in livestock, particularly pigs, raising questions about its success.
  • Understanding the molecular mechanisms behind MRSA ST398's prevalence requires investigating its genetic makeup, including virulence and antimicrobial resistance genes.

Purpose of the Study:

  • To compare the carriage of virulence and antimicrobial resistance genes across various Staphylococcus aureus sequence types (STs) and clonal complexes (CCs), with a focus on ST398.
  • To identify potential molecular mechanisms contributing to the success of the MRSA ST398 lineage.

Main Methods:

  • Screening of S. aureus strains from multiple STs/CCs (including ST398) using DNA microarray and PCR.
  • Analysis of virulence and antimicrobial resistance gene carriage within and between different ST/CC groups.

Main Results:

  • Isolates within the same ST/CC shared similar virulence gene profiles; ST398 had the lowest content of virulence genes, lacking accessory virulence factors found in other ST/CCs.
  • Antimicrobial resistance gene profiles varied within ST/CCs, with MRSA ST398 showing significant diversity and a high content of resistance genes, comparable to some MRSA ST8.
  • No ST398-specific virulence markers were identified, indicating a unique genetic background for this lineage.

Conclusions:

  • MRSA ST398 possesses a distinct genetic profile characterized by reduced virulence factors but significant antimicrobial resistance.
  • The success of MRSA ST398 is not attributed to specific virulence markers but rather a unique genetic background and high resistance gene content.

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