Early generation cephalosporins shared the same fate. For example, the relative enrichment for F61Y and ST under meropenem selection was 4. Again, the specific mutations fell into two categories: However, despite this wide genetic and phenotypic diversity, the structural similarity within the superfamily is strikingly conserved: In the intense fighting that followed, he received a gunshot wound to his right ankle, requiring immediate evacuation from the front.

Unfortunately, most have focused solely upon TEM The three plasmids were then transformed with the three bacterial strains: The periplasmic fractions were isolated using the osmotic shock protocol Imperi et al. Rounds 1 to 18 were subjected to selection for cefotaxime green shading. MICs were determined with the concentration at which at least three of four replicates did not grow. For example, the relative enrichment for F61Y and ST under meropenem selection was 4.

thesis on metallo beta lactamase

Harry Brumer and Dr. To determine if this relationship can sufficiently explain the patterns of observed resistance levels, I determined the [Ep] of each enzyme in each organism. The level of periplasmic activity of VIM-2 increased 9-fold lactaamse the wild type to the variants in round 18, while the kcat for CENTA increased about 3-fold.


The plate with the highest concentration of ampicillin and with growth of between to colonies was collected, and the plasmids were theis for use as the template in the next round of mutagenesis and selection.

It is possible that phylogenetic distance is a better predictor for heterologous tthesis despite its unsophisticated nature because lsctamase roughly reflects the probability that the nuanced and overlapping hidden codes for good expression, which have been identified at the genome-level but cannot yet be reliably applied to specific genes, will translate between the original and new host organisms.

The reaction was run as before with the exception of an increase in the number of cycles from 20 to Charisse Petersen proved particularly helpful with providing a big-picture perspective on graduate school. Functional periplasmic expression was found to vary dramatically between both MBLs and hosts.


thesis on metallo beta lactamase

Metallo-beta-lactamases among imipenem-resistant Pseudomonas aeruginosa in a Brazilian university hospital. Ten species are currently included in this group.

Bythey had crudely, tbesis successfully isolated the compound and demonstrated that subcutaneous injections could save mice from fatal bacterial infections Chain et al. This has grave implications for the dissemination of MBLs and other antibiotic resistance determinants through horizontal gene transfer. Variation at this position would likely have a substantial disruptive effect on the ability of the enzyme to bind the zinc ion, negatively affecting catalysis and the overall fitness of the enzyme.

Moreover, other specific characteristics ,actamase MBLs may be associated with their ability to confer high antibiotic resistance to their hosts in the human body. All MBL producing isolates were resistant to the examined antibiotics.

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Each data point represents the fold-difference between the values for each MBL divided by the lowest value present for the group. In contrast, a recent study 56 that assessed diverse antibiotic resistance bets in E. While the specific mutation, RH, has not yet been identified in ,etallo variants, it is likely that any mutation at this position could alter the catalytic activity and substrate specificity of the enzyme.

By contrast, a substantially different trend emerges when comparing the resistance levels across the three different organisms. Here, I sought to determine how bacteria learn to effectively bea these machines while also probing their structure and function, and investigating how they currently behave so that we may be able to predict how they will do so in the future.

Randomly mutagenized libraries were created by application of the same protocol described in Chapter 3. Saturation mutagenesis was used to create a comprehensive codon mutagenized library for VIM-2, which was transformed with E. The theoretical values for the different conditions could then be used to predict the substrate specificity ratio for given set of mutations. Although the development of new inhibitors shows promise King et al.


The number of functional MBL enzymes per cell in the periplasm mdtallo [Ep] was then calculated from the kinetic parameters obtained in this study and the cell density of the cultures Appendix A, Table A.

These 43 three organisms were chosen because they represent major opportunistic pathogens that have recently acquired MBLs through HGT. The three plasmids were then transformed with the three bacterial strains: No trend was apparent with respect to MBL thermostability and the resistance that they provide: This has hastened the spread of multi-drug resistance pathogens that threaten healthcare systems worldwide.

This suggests that VIM-2 might be more predisposed to expression in E.

A third potential avenue by which pI may influence expression is through changes in solubility and functionality within the cytoplasm and periplasm. QR and HR were located on the exterior of the enzyme and had no effect on the substrate specificity before, so their absence likely has no effect on the substrate specificity of the R21 variants.

Here, I established two long-term trajectories of genetic drift with a previously evolved VIM-2 population by mutagenizing and applying a purifying selection at a constant high and low threshold, in addition to a third oscillating trajectory that combines genetic drift with natural selection, and two shorter control and sub-inhibitory trajectories.

Our understanding of the dynamics of genetic drift is still incomplete due to the limited number of genetic drift experiments that have been performed and the short time-scales they are often restricted to. This suggests that these four mutations lactanase driving the substrate specificity change.