A Population-Based Approach to the Study of Virulence Determinants in Methicillin-Resistant Staphylococcus Aureus

Abstract

This study aims to provide insights into the application of next generation sequencing for the study of hospital-acquired staphylococcal infections. Staphylococcus aureus is a gram positive, commensal species of bacteria that are a common constituent of the human microbiome. However, many of the strains of this opportunistic pathogen, the causative agent of a wide range of infections, have now acquired resistance to many frequently used antibiotics. At its worst, the threat of antimicrobial resistance could result in increased rates of post-surgical mortality for even routine surgical procedures and, generally, make clinical facilities potential epicentres for infection outbreaks.

With that in mind, this body of work will focus largely on methicillin resistant S. aureus (MRSA), given its relevance in clinical environments currently. A metagenomic approach was used in an attempt to monitor the transmission of microbial pathogens upon the relocation of a paediatric burns unit from one site to another, however an unfortunate technical oversight prevented with project from being completed.

In the study of an epidemic strain ST228, an attempt was also made at establishing any causal relationships between bacterial phenotypes and their ability to disseminate to the scale of an outbreak, however no inferences could be gleaned from the study of biofilm formation, toxin production and phage susceptibility in select isolates from the ST228 cohort, warranting further study.

Finally, a GWAS was carried out on a cohort of ST239 isolates for biofilm formation and protease activity. The protease GWAS identified potential associations with certain loci in the TW20 reference genome, however either the lack of sensitivity of the assay used or inherent differences between the proteolytic potential of ST239 and the USA300_FPR3757 strain that made up the available transposon mutant library meant that the dataset was ultimately inconclusive. Five genes (mecA, sgaT, ccrB, aap and hyp) were identified as potentially being associated to biofilm formation in ST239. Verification of these associations through complementation was unsuccessful. Ultimately, despite some technical issues, the analysis of whole genomic sequence data combined with the screening of a large collection of ST239 isolates identified a handful of potentially novel effectors of biofilm formation that warrant additional characterization in the future.

Date of Award	13 Feb 2019
Original language	English
Awarding Institution	University of Bath
Supervisor	Ruth Massey (Supervisor) & Toby Jenkins (Supervisor)