DOI
https://doi.org/10.25772/FW3R-Q346
Defense Date
2015
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Microbiology & Immunology
First Advisor
Dr. Gordon L. Archer
Abstract
The gene encoding methicillin resistance in Staphylococcus aureus (MRSA) is carried in the chromosome on a large genomic island called SCCmec and is always inserted at the att site within orfX. SCCmec has been designated a mobile genetic element but a mechanism by which it moves among different strains and species of staphylococci has never been demonstrated. This work shows that bacteriophage 80α is capable of transducing SCCmec into a recipient cell, after which it can integrate into the bacterial chromosome via homologous recombination. More importantly, this work characterizes a conjugative mechanism of SCCmec transfer. Results demonstrate the capture of a 30.8 kb SCCmec element on a conjugative plasmid for the first time, its transfer into both S. aureus and S. epidermidis recipients, and its excision from the plasmid with insertion in the orfX att site in recipients. The element was integrated into the plasmid by recombination between IS elements invariably present on all SCCmec types and pGO1/pSK41-like conjugative plasmids. These data explain the movement of SCCmec from reservoirs in commensal coagulase-negative staphylococci into different Staphylococcus aureus lineages using a ubiquitous conjugative plasmid that can transfer among staphylococci of different species and, thus, describes a mechanism for the environmental dissemination of methicillin resistance in nature.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
7-27-2015