Adaptive change inferred from genomic population analysis of the ST93 epidemic clone of community-associated methicillin-resistant Staphylococcus aureus

T.P. Stinear; K.E. Holt; K. Chua; J. Stepnell; K.L. Tuck; G. Coombs; P.F. Harrison; T. Seemann; B.P. Howden

doi:10.1093/gbe/evu022

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Adaptive change inferred from genomic population analysis of the ST93 epidemic clone of community-associated methicillin-resistant Staphylococcus aureus

Journal article

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Adaptive change inferred from genomic population analysis of the ST93 epidemic clone of community-associated methicillin-resistant Staphylococcus aureus

T.P. Stinear, K.E. Holt, K. Chua, J. Stepnell, K.L. Tuck, G. Coombs, P.F. Harrison, T. Seemann and B.P. Howden

Genome Biology and Evolution, Vol.6(2), pp.366-378

2014

DOI: https://doi.org/10.1093/gbe/evu022

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Abstract

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a major public health problem around the world. In Australia, ST93-IV[2B] is the dominant CA-MRSA clone and displays significantly greater virulence than other S. aureus. Here, we have examined the evolution of ST93 via genomic analysis of 12MSSA and 44MRSAST93 isolates, collected from around Australia over a 17-year period. Comparative analysis revealed a core genome of 2.6Mb, sharing greater than 99.7% nucleotide identity. The accessory genome was 0.45Mb and comprised additional mobile DNA elements, harboring resistance to erythromycin, trimethoprim, and tetracycline. Phylogenetic inference revealed amolecular clock and suggested that a single clone of methicillin susceptible, Panton-Valentine leukocidin (PVL) positive, ST93 S. aureus likely spread from North Western Australia in the early 1970s, acquiring methicillin resistance at least twice in the mid 1990s. We also explored associations between genotype and important MRSA phenotypes including oxacillin MIC and production of exotoxins (a-hemolysin [Hla], d-hemolysin [Hld], PSMa3, and PVL). High-level expression of Hla is a signature feature of ST93 and reduced expression in eight isolates was readily explained by mutations in the agr locus. However, subtle but significant decreases in Hldwere also noted over time that coincided with decreasing oxacillin resistance and were independent of agr mutations. The evolutionof ST93 S. aureus is thus associated with a reductionin both exotoxin expression and oxacillin MIC, suggesting MRSA ST93 isolates are under pressure for adaptive change.

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Title: Adaptive change inferred from genomic population analysis of the ST93 epidemic clone of community-associated methicillin-resistant Staphylococcus aureus
Authors/Creators: T.P. Stinear (Author/Creator)
K.E. Holt (Author/Creator)
K. Chua (Author/Creator)
J. Stepnell (Author/Creator)
K.L. Tuck (Author/Creator)
G. Coombs (Author/Creator)
P.F. Harrison (Author/Creator)
T. Seemann (Author/Creator)
B.P. Howden (Author/Creator)
Publication Details: Genome Biology and Evolution, Vol.6(2), pp.366-378
Publisher: Oxford University Press
Identifiers: 991005541018107891
Copyright: © The Author(s) 2014.
Murdoch Affiliation: Murdoch University
Language: English
Resource Type: Journal article

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Collaboration types: Domestic collaboration
Citation topics: 1 Clinical & Life Sciences; 1.23 Antibiotics & Antimicrobials; 1.23.173 MRSA and VRE
Web Of Science research areas: Evolutionary Biology; Genetics & Heredity
ESI research areas: Molecular Biology & Genetics