The molecular epidemiology and characteristics of methicillin resistant Staphylococcus aureus sequence type 22 in a local, national and international context.

Thomson, Calum Bryson (2017). The molecular epidemiology and characteristics of methicillin resistant Staphylococcus aureus sequence type 22 in a local, national and international context. University of Birmingham. Ph.D.

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Abstract

The globally distributed, ciprofloxacin resistant hospital associated methicillin resistant Staphylococcus aureus (MRSA) lineage epidemic (E)MRSA-15 (sequence type 22) continues to expand into new healthcare systems around the world. To further understand the evolution of EMRSA-15, which has been proposed to have emerged in the West Midlands, a large collection of contemporaneous and historical Birmingham isolates were studied alongside a collection of International genomes. Through generation of phylogentic trees this study has been able to determine that EMRSA-15 emerged in c1984 and that during this time a highly related healthcare associated ciprofloxacin sensitive ST22 population was present in Birmingham. A dominant, geographically restricted EMRSA-15 clone was also identified in Birmingham (designated the BHM clone). Analysis of the impact of fluoroquinolone use on the Birmingham EMRSA-15 phylogeny showed increasing use of fluoroquinolones (the introduction of ofloxacin) coincided with the emergence of the BHM clone. Further evidence of geographically restricted EMRSA-15 clones were found in Guernsey and Hong Kong; demonstrating localized evolution giving rise to distinct island populations. Comparison of the desiccation tolerance of geographically restricted and non-restricted EMRSA-15 clones indicated enhanced environmental survival as a possible reason for the spread and dominance of the restricted lineages.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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