{"id":{"repo_id":"creighton","oai_identifier":"oai:cdr.creighton.edu:10504/47482"},"canonical_url":"https://search.dev.ndltd.org/etd/creighton/oai:cdr.creighton.edu:10504/47482","repository":{"repo_id":"creighton","name":"Creighton University","base_url":"https://cdr.creighton.edu/server/oai/request"},"display":{"title":"Mechanisms Involved in the Expression of the AmpC Beta-lactamase Gene blaCMY-2 in Escherichia coli","abstract":"Enterobacteriaceae that express plasmid-encoded AmpC β-lactamases can be resistant to third generation cephalosporins and β-lactam/β-lactamase inhibitor combinations. Infections by these bacteria are associated with increased patient morbidity and mortality. Little is known about how plasmid-encoded AmpC genes are regulated or expressed. The experiments described in this dissertation sought to determine mechanisms that influence the transcription of blaCMY-2; the most common plasmid-encoded AmpC β-lactamase gene found in E. coli worldwide. Four clinical piperacillin/tazobactam-susceptible E. coli parent strains carrying blaCMY-2 and twelve piperacillin/tazobactam-resistant mutants selected from the parent strains were the focus of study. It was hypothesized that sequence changes upstream of blaCMY-2 were driving increased blaCMY-2 expression and enabling resistance to piperacillin/tazobactam in the mutants. It was also hypothesized that transcription factors binding to sequence upstream of blaCMY-2 promoter regions were influencing expression. Three important findings were made testing these hypotheses. 1) It was found that only 33% of the piperacillin/tazobactam-resistant mutants were overexpressing blaCMY-2. No upstream sequence changes were found in blaCMY-2 overexpressing mutant strains. For all overexpression mutants, changes in blaCMY-2 transcript level were associated with increased copy number of their blaCMY-2 encoded plasmid. Two mutants with blaCMY-2 on a 100 kb IncI1 plasmid had point mutations in the inc antisense RNA gene that controls IncI1 copy number. 2) Examination of upstream sequence for two parent strains identified a novel divergent tandem blaCMY-2 arrangement flanking an IS5 insertion element. Strains with this feature had 2-fold higher blaCMY-2 expression than a single arrangement strain. 3) The transcriptional activator Rob was identified binding sequence upstream of the distal blaCMY-2 promoter sequence within the insertion element ISEcp1. Additional studies indicated Rob was activated by β-lactam exposure and therefore may enhance blaCMY-2 expression when β-lactams are present. Further work will be needed to determine how gene copy number and Rob play a role in β-lactam resistance among clinical E. coli strains carrying blaCMY-2 .","abstract_html":"Enterobacteriaceae that express plasmid-encoded AmpC β-lactamases can be resistant to third generation cephalosporins and β-lactam/β-lactamase inhibitor combinations. Infections by these bacteria are associated with increased patient morbidity and mortality. Little is known about how plasmid-encoded AmpC genes are regulated or expressed. The experiments described in this dissertation sought to determine mechanisms that influence the transcription of blaCMY-2; the most common plasmid-encoded AmpC β-lactamase gene found in E. coli worldwide. Four clinical piperacillin/tazobactam-susceptible E. coli parent strains carrying blaCMY-2 and twelve piperacillin/tazobactam-resistant mutants selected from the parent strains were the focus of study. It was hypothesized that sequence changes upstream of blaCMY-2 were driving increased blaCMY-2 expression and enabling resistance to piperacillin/tazobactam in the mutants. It was also hypothesized that transcription factors binding to sequence upstream of blaCMY-2 promoter regions were influencing expression. Three important findings were made testing these hypotheses. 1) It was found that only 33% of the piperacillin/tazobactam-resistant mutants were overexpressing blaCMY-2. No upstream sequence changes were found in blaCMY-2 overexpressing mutant strains. For all overexpression mutants, changes in blaCMY-2 transcript level were associated with increased copy number of their blaCMY-2 encoded plasmid. Two mutants with blaCMY-2 on a 100 kb IncI1 plasmid had point mutations in the inc antisense RNA gene that controls IncI1 copy number. 2) Examination of upstream sequence for two parent strains identified a novel divergent tandem blaCMY-2 arrangement flanking an IS5 insertion element. Strains with this feature had 2-fold higher blaCMY-2 expression than a single arrangement strain. 3) The transcriptional activator Rob was identified binding sequence upstream of the distal blaCMY-2 promoter sequence within the insertion element ISEcp1. Additional studies indicated Rob was activated by β-lactam exposure and therefore may enhance blaCMY-2 expression when β-lactams are present. Further work will be needed to determine how gene copy number and Rob play a role in β-lactam resistance among clinical E. coli strains carrying blaCMY-2 .","abstract_has_math":false,"creators":["Kurpiel, Philip Marion"],"institution":"Creighton University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Hanson, Nancy D."],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013-12-09","date_published":"2013-12-09","updated_at":"2026-07-24T01:51:19Z","subjects":[],"languages":["en_US"],"rights":["Copyright is retained by the Author. A non-exclusive distribution right is granted to Creighton University and to ProQuest following the publishing model selected above."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10504/47482","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Hanson, Nancy D."]},{"key":"dc:creator","label":"Author","values":["Kurpiel, Philip Marion"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-01-06T15:25:34Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2015-12-31T09:40:18Z"]},{"key":"dc:date.issued","label":"Date","values":["2013-12-09"]},{"key":"dc:publisher","label":"Institution","values":["Creighton University"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright is retained by the Author. A non-exclusive distribution right is granted to Creighton University and to ProQuest following the publishing model selected above."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10504/47482"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Enterobacteriaceae that express plasmid-encoded AmpC β-lactamases can be resistant to third generation cephalosporins and β-lactam/β-lactamase inhibitor combinations. Infections by these bacteria are associated with increased patient morbidity and mortality. Little is known about how plasmid-encoded AmpC genes are regulated or expressed. The experiments described in this dissertation sought to determine mechanisms that influence the transcription of blaCMY-2; the most common plasmid-encoded AmpC β-lactamase gene found in E. coli worldwide. Four clinical piperacillin/tazobactam-susceptible E. coli parent strains carrying blaCMY-2 and twelve piperacillin/tazobactam-resistant mutants selected from the parent strains were the focus of study. It was hypothesized that sequence changes upstream of blaCMY-2 were driving increased blaCMY-2 expression and enabling resistance to piperacillin/tazobactam in the mutants. It was also hypothesized that transcription factors binding to sequence upstream of blaCMY-2 promoter regions were influencing expression. Three important findings were made testing these hypotheses. 1) It was found that only 33% of the piperacillin/tazobactam-resistant mutants were overexpressing blaCMY-2. No upstream sequence changes were found in blaCMY-2 overexpressing mutant strains. For all overexpression mutants, changes in blaCMY-2 transcript level were associated with increased copy number of their blaCMY-2 encoded plasmid. Two mutants with blaCMY-2 on a 100 kb IncI1 plasmid had point mutations in the inc antisense RNA gene that controls IncI1 copy number. 2) Examination of upstream sequence for two parent strains identified a novel divergent tandem blaCMY-2 arrangement flanking an IS5 insertion element. Strains with this feature had 2-fold higher blaCMY-2 expression than a single arrangement strain. 3) The transcriptional activator Rob was identified binding sequence upstream of the distal blaCMY-2 promoter sequence within the insertion element ISEcp1. Additional studies indicated Rob was activated by β-lactam exposure and therefore may enhance blaCMY-2 expression when β-lactams are present. Further work will be needed to determine how gene copy number and Rob play a role in β-lactam resistance among clinical E. coli strains carrying blaCMY-2 ."]},{"key":"dc:title","label":"Title","values":["Mechanisms Involved in the Expression of the AmpC Beta-lactamase Gene blaCMY-2 in Escherichia coli"]}]}],"canonical_facts":{"dc:contributor.advisor":["Hanson, Nancy D."],"dc:creator":["Kurpiel, Philip Marion"],"dc:date.accessioned":["2014-01-06T15:25:34Z"],"dc:date.available":["2015-12-31T09:40:18Z"],"dc:date.issued":["2013-12-09"],"dc:description.abstract":["Enterobacteriaceae that express plasmid-encoded AmpC β-lactamases can be resistant to third generation cephalosporins and β-lactam/β-lactamase inhibitor combinations. Infections by these bacteria are associated with increased patient morbidity and mortality. Little is known about how plasmid-encoded AmpC genes are regulated or expressed. The experiments described in this dissertation sought to determine mechanisms that influence the transcription of blaCMY-2; the most common plasmid-encoded AmpC β-lactamase gene found in E. coli worldwide. Four clinical piperacillin/tazobactam-susceptible E. coli parent strains carrying blaCMY-2 and twelve piperacillin/tazobactam-resistant mutants selected from the parent strains were the focus of study. It was hypothesized that sequence changes upstream of blaCMY-2 were driving increased blaCMY-2 expression and enabling resistance to piperacillin/tazobactam in the mutants. It was also hypothesized that transcription factors binding to sequence upstream of blaCMY-2 promoter regions were influencing expression. Three important findings were made testing these hypotheses. 1) It was found that only 33% of the piperacillin/tazobactam-resistant mutants were overexpressing blaCMY-2. No upstream sequence changes were found in blaCMY-2 overexpressing mutant strains. For all overexpression mutants, changes in blaCMY-2 transcript level were associated with increased copy number of their blaCMY-2 encoded plasmid. Two mutants with blaCMY-2 on a 100 kb IncI1 plasmid had point mutations in the inc antisense RNA gene that controls IncI1 copy number. 2) Examination of upstream sequence for two parent strains identified a novel divergent tandem blaCMY-2 arrangement flanking an IS5 insertion element. Strains with this feature had 2-fold higher blaCMY-2 expression than a single arrangement strain. 3) The transcriptional activator Rob was identified binding sequence upstream of the distal blaCMY-2 promoter sequence within the insertion element ISEcp1. Additional studies indicated Rob was activated by β-lactam exposure and therefore may enhance blaCMY-2 expression when β-lactams are present. Further work will be needed to determine how gene copy number and Rob play a role in β-lactam resistance among clinical E. coli strains carrying blaCMY-2 ."],"dc:identifier.uri":["http://hdl.handle.net/10504/47482"],"dc:language.iso":["en_US"],"dc:publisher":["Creighton University"],"dc:rights":["Copyright is retained by the Author. A non-exclusive distribution right is granted to Creighton University and to ProQuest following the publishing model selected above."],"dc:title":["Mechanisms Involved in the Expression of the AmpC Beta-lactamase Gene blaCMY-2 in Escherichia coli"],"dc:type":["Dissertation"]},"updated_at":"2026-07-24T01:51:19Z"}