Liljebjelke, Karen A.Guardado Servellón, Fernando Joaquín2020-09-252020-09-252020-09-21Guardado Servellón, F. J. (2020). Investigation of the Co-occurrence of Zinc and Copper Resistance and Antimicrobial Resistance in Escherichia coli from Beef Cattle Production Systems (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/112573The present set of studies was directed towards determining the relationship between zinc (Zn) and copper (Cu) resistance and antimicrobial resistance in Escherichia coli from beef cattle production systems. First, a spectrophotometric assay was developed to properly assess the resistance levels of both Zn and Cu in Escherichia coli. The method was standardized for E. coli and it displayed a good linear dynamic range (R2>0.95), and precision (RSD< 35% in all but three Zn concentrations). The MIC for the E. coli reference strain (ATCC 25922) were 2.78 mol/ml and 8.41 mol/ml for Zn and Cu respectively. In the second study, we determined antimicrobial phenotypes and the Zn and Cu resistance levels for E. coli isolates from environmental samples obtained from W.A Ranches. The samples analyzed had a low prevalence of antimicrobial resistance as 31/39 isolates were susceptible to all the antimicrobials tested using the disc diffusion method. The most common resistance was ampicillin (4/39) and amoxicillin-clavulanic acid (4/39), with one isolate being resistant to doxycycline. All the isolates resistant to ampicillin were also resistant to amoxicillin-clavulanic acid. The isolates were then tested for Zn and Cu resistance using the assay developed. Seven of the eight isolates with resistant or intermediate antimicrobial resistance patterns showed higher optical density (OD) in the Zn and Cu resistance spectrophotometric assay when compared to the reference strain. Fisher’s exact test was conducted to compare antimicrobial-resistant (all antimicrobials) and susceptible isolates in their resistance to Zn and Cu, with the results showing that the antimicrobial-resistant isolates are also more likely to have a higher resistance to Zn (p value<0.001) and Cu (p value=0.013) as indicated by higher absorbance units (AU). A Principal Component Analysis showed the clustering of 6/8 antimicrobial-resistant isolates based on the Zn and Cu resistance meaning that resistance to these metals might be an indicator of antimicrobial resistance.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.MicrobiologyVeterinary Sciencemaster thesis10.11575/PRISM/38233