Use this URL to cite or link to this record in EThOS:
Title: Surface colonisation and survival of Staphylococcus aureus
Author: Salgado, B. A.
ISNI:       0000 0004 7970 4835
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
Availability of Full Text:
Access from EThOS:
Access from Institution:
Staphylococcus aureus nasal persistently colonises the nasal cavity of 20% of the human global population and a further proportion is frequently transiently colonised. Prevention of S. aureus colonisation reduces transmission and minimizes infections caused by this microorganism, which range from minor skin infections to life-threatening diseases. In this study, a murine nasopharyngeal colonisation model was established and then used for three serial passages of seven days with S. aureus. During the evolutionary timescale, a pronounced genetic variation was identified among the surviving colonising isolates, demonstrating that S. aureus mutations are naturally selected against the selective pressures in the nasopharynx niche. DNA Sequence variants were mainly found in genes that encode proteins with roles in DNA and RNA activity and those involved in carbohydrate and amino acid metabolism and stress responses. S. aureus nasopharyngeal evolved clones revealed a trend for increased fitness as evidenced by some weak statistical support for increased frequency of colonisation in the murine nasopharynx. This observation provides some support for the selection of sequence variants resulting in adaptive responses to the niche. Over the course of this study, intra-species competition for the nasopharynx niche was observed, whereby a S. aureus strain already colonising mice (named SA_MOU) prevented invasion by the experimental S. aureus strain after its inoculation. Although the competitor strains are closely related to USA300 (both belong to ST8), the SA_MOU genome sequence did not reveal strong evidence for similar genetic adaptation to the nasopharynx as that identified via the SNPs of USA300 LAC JE2 after serial passages of the murine nasopharynx. This study has increased our understanding of S. aureus adaptive responses to selective pressures in the nasopharynx, which could contribute to future novel strategies aimed at inhibiting human nasal carriage of S. aureus.
Supervisor: Horsburgh, Malcolm ; Kadioglu, Aras Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral