The Effect of Intracellular Zinc Levels in Escherichia coli on Metallo-β-Lactamase Activity

Author(s)

Jill Thompson

Date Approved

6-2019

Document Type

Thesis

Degree Name

MS, Molecular Pathology and Immunology

Department

Molecular Biology

College

Graduate School of Biomedical Sciences

First Advisor

Salvatore Caradonna, PhD

Committee Member 1

Scott Gygax, PhD

Committee Member 2

David Hilbert, PhD

Subject(s)

beta-Lactamases; beta-Lactam Resistance; Drug Resistance; Escherichia coli; Multiple Antibacterial Drug Resistance; Antibacterial Drug Resistance; Zinc

Disciplines

Bacteriology | Cell Biology | Immunopathology | Molecular Biology | Molecular Genetics | Pathogenic Microbiology

Abstract

Antibiotic resistance is a consequence of evolution via natural selection and poses a serious threat to the world's population. Escherichia coli, and other bacterial species, have acquired genes encoding Metallo-β-Lactamases (MBLs). MBLs are zinc-dependent enzymes that degrade most β-lactam antibiotics, and have emerged as important antibacterial resistance determinants in multidrug resistant pathogens. There are several different families of MBLs, and the major clinically relevant ones are Verona Integrated-encoded Metallo-β-Lactamases (VIMs), Imipenemases (IMPs), and New Delhi Metallo-β-Lactamases (NDMs). These enzymes confer high level resistance to penicillins, cephalosporins, and carbapenems, and are not inhibited by FDA-approved β-lactamase inhibitors. Variants of NDM have been identified that exhibit varying degrees of zinc-dependency. The first NDM discovered, NDM-1, has decreased β-lactamase activity when zinc levels are reduced. However, newly emerged NDM alleles (e.g. NDM-4 and NMD-12) have mutations such as the M154L substitution that enable the enzyme to function better at reduced zinc levels compared to the NDM-1 allele. This project looks at genes that have an effect on the intracellular zinc levels in E. coli, and how knocking them out, and therefore altering intracellular zinc levels, can affect the activity of NDM-1 and its M154L variant. It also looks at what effect altering zinc levels has on the other clinically relevant MBLs (VIM and IMP), along with MCR-1 which is another zinc-dependent enzyme that confers resistance to colistin, a different non- β -lactam antibiotic. Lastly, this project evaluated KPC-2, a non-zinc-dependent carbapenemase, as a control enzyme. As MBLs confer resistance to an important class of antibiotic, it's important to look at what interventions can be used to counteract their β-lactamase activity, as they could eventually be used as targets for inhibition that restore the activity of β-lactam antibiotics against pathogens expressing these enzymes.

Recommended Citation

Thompson, Jill, "The Effect of Intracellular Zinc Levels in Escherichia coli on Metallo-β-Lactamase Activity" (2019). Graduate School of Biomedical Sciences Theses and Dissertations. 66.
https://rdw.rowan.edu/gsbs_etd/66