While antibiotics have saved the lives of millions of people since the discovery of the first β-lactam, penicillin, their continued effectiveness is being increasingly threatened by resistant bacteria. Bacterial resistance to β-lactams is mainly achieved through the production of serine-β-lactamases (SBLs) and metallo-β-lactamases (MBLs). Although both types of β-lactamases are commonly isolated in clinical settings, MBLs represent the greatest threat to public health since they are resistant to SBL inhibitors and most β-lactams. However, aspergillomarasmine A (AMA), a fungal natural product synthesized by Aspergillus versicolor, was shown to be a rapid and potent inhibitor against two clinically relevant MBLs: NDM-1 and VIM-2. In bacteria possessing these enzymes, AMA could rescue the activity of meropenem, a broad-spectrum β-lactam that is usually reserved for the treatment of the most severe bacterial infections. However, many questions remain revolving around AMA's inhibitory potency and spectrum. Therefore, the activity of AMA in combination with six β-lactams from three subclasses (carbapenem, penam, cephem) was explored against 19 MBLs from three subclasses (B1, B2, B3). After determining that AMA activity was linked to MBL zinc affinity and that AMA was more potent when paired with a carbapenem, the efficacy of an AMA/meropenem combination was evaluated with and without avibactam, a potent SBL inhibitor. This study used ten Escherichia coli and ten Klebsiella pneumoniae laboratory strains as well as 30 clinical strains producing at least one MBL and one SBL. Once establishing that the AMA/avibactam/meropenem combination was effective against carbapenemase-producing Enterobacterales, new Acinetobacter and Pseudomonas shuttle vectors were created. With these shuttle vectors, it was determined that the AMA/avibactam/meropenem combination was effective against some of the bacteria topping the World Health Organization’s priority pathogen list. / Thesis / Doctor of Philosophy (PhD) / Bacteria are all around us. While some bacteria can promote human health, others can cause serious infections. These infections are typically treated with antibiotics. β-Lactam antibiotics, such as penicillins and cephalosporins, are especially important to medicine. Unfortunately, an increasing number of bacteria employ enzymes, known as β-lactamases, which negate the effects of β-lactam antibiotics. Previous studies demonstrated that a natural product, known as aspergillomarasmine A (AMA), could inhibit some β-lactamase enzymes. Consequently, the inhibitory power of AMA was further explored against a larger number of β-lactamase enzymes and in combination with different β-lactam antibiotics. After discovering that AMA had more inhibitory power when combined with a β-lactam antibiotic known as meropenem, the efficacy of the AMA/meropenem pairing was evaluated against resistant bacteria in the presence and absence of avibactam, another β-lactamase inhibitor. The AMA/avibactam/meropenem combination was shown to be effective against some of the world’s most antibiotic-resistant bacteria.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27972 |
| Date | 11 1900 |
| Creators | Rotondo, Caitlyn Michelle |
| Contributors | Wright, Gerard, Biochemistry and Biomedical Sciences |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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