Dissemination of Antibiotic Resistant Bacteria and Plasmids Encoding Antibiotic Resistance Genes in the Environment
Rahube, Teddie Onkabetse
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Multi-drug resistant (MDR) bacteria (also referred to as superbugs) are classified among the world’s leading cause of death in humans. The continued emergence and spread of antibiotic resistance genes (ARGs) among different bacteria in clinical and non-clinical environments is cause for concern. Identifying and studying important reservoirs could lead to understanding of persistence, transfer and dissemination of these bacteria and ARGs from environmental sources to humans. The specific objectives of this study are to; a) Investigate the role computer keyboards may play as an environmental reservoir for community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) using culture based and molecular tools. b) Isolate plasmids encoding multiple antibiotic resistance genes from swine manure, analyze the conjugative mobility, and detect plasmid-specific sequences in the soil following manure application using PCR method. c) Characterize antibiotic resistance plasmids and bacterial communities isolated from a municipal wastewater treatment plant environment using comparative genomics approach and denaturing gradient gel electrophoresis (DGGE) microbial profiling method. d) Analyze the functions of the plasmids replication, conjugative mobility and maintenance genes by in vitro techniques, detect and quantify the plasmid-associated resistance determinants in the environment upstream and downstream of the wastewater treatment plant (WWTP) using molecular methods. During the course of this research, I have isolated a CA-MRSA strain (Lum 1) from one of the computer keyboards surveyed from different high schools in and around Regina. Lum 1 is characterized by the presence of mecA gene, which codes for resistance to methicillin, and a spa type t128 found in the CA-MRSA strain lineage CMRSA 7/US400. I have also isolated and characterized five plasmids from swine manure and WWTP environments, these plasmids carry multiple resistance genes to clinically relevant antibiotics (macrolides, tetracyclines, beta-lactams, chloramphenicol, sulfonamides, aminoglycosides, trimethoprim), quaternary ammonium compounds and heavy metals (mercury, chromium and zinc). Analysis of the plasmids conjugative mobility and stability have provided insights about the possible persistence and transfer of ARGs to bacterial communities in the environments receiving waste effluent and livestock manure. Using molecular PCR tools, I have also detected and quantified the plasmid sequences and resistance determinants in manure-amended soil and effluent influenced water ecosystems.