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Factors influencing gene expression and resistance for Gram-negative organisms expressing plasmid-encoded ampC genes of Enterobacter origin
High-level expression of AmpC β-lactamases results in organisms resistant to multiple β-lactam antibiotics. The mechanism of chromosomally mediated AmpC resistance has been elucidated, however the mechanism(s) driving plasmid-encoded AmpC resistance are unknown. Studies were designed to identify fac...
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Published in: | Journal of antimicrobial chemotherapy 2003-05, Vol.51 (5), p.1141-1151 |
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description | High-level expression of AmpC β-lactamases results in organisms resistant to multiple β-lactam antibiotics. The mechanism of chromosomally mediated AmpC resistance has been elucidated, however the mechanism(s) driving plasmid-encoded AmpC resistance are unknown. Studies were designed to identify factors which influence expression of plasmid-encoded ampC genes and correlate these factors with resistance. As the model system, ampC genes of Enterobacter origin were used to determine how gene copy number, genetic background and genetic organization influenced resistance phenotypes. To this end, gene expression from the plasmid-encoded inducible blaACT-1 and non-inducible blaMIR-1 were compared with chromosomal ampC gene expression from both wild-type (WT) and derepressed Enterobacter cloacae isolates. RNA levels within the original clinical isolates were examined using primer extension analysis, whereas a new PCR strategy was developed to examine gene copy number. These data revealed that blaACT-1 and blaMIR-1 constitutive expression was 33- and 95-fold higher than WT expression, whereas copy numbers of the plasmid-encoded genes were 2 and 12, respectively. Differences in promoters and transcriptional starts for the respective plasmid-encoded genes were noted and contribute to increases observed in overall expression. Finally, β-lactam MICs were increased two- to 16-fold when blaACT-1 was expressed in Escherichia coli AmpD– strains compared with E. coli AmpD+ strains. In conclusion, high-level expression of plasmid-encoded ampC genes requires interplay between multiple factors including genetic organization, promoter modifications, genetic background, and to some extent gene copy number. In addition, clinical laboratories need to be aware that genetic backgrounds of inducible plasmid-encoded genes can dramatically influence MICs for organisms not normally associated with derepressed phenotypes. |
doi_str_mv | 10.1093/jac/dkg204 |
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The mechanism of chromosomally mediated AmpC resistance has been elucidated, however the mechanism(s) driving plasmid-encoded AmpC resistance are unknown. Studies were designed to identify factors which influence expression of plasmid-encoded ampC genes and correlate these factors with resistance. As the model system, ampC genes of Enterobacter origin were used to determine how gene copy number, genetic background and genetic organization influenced resistance phenotypes. To this end, gene expression from the plasmid-encoded inducible blaACT-1 and non-inducible blaMIR-1 were compared with chromosomal ampC gene expression from both wild-type (WT) and derepressed Enterobacter cloacae isolates. RNA levels within the original clinical isolates were examined using primer extension analysis, whereas a new PCR strategy was developed to examine gene copy number. These data revealed that blaACT-1 and blaMIR-1 constitutive expression was 33- and 95-fold higher than WT expression, whereas copy numbers of the plasmid-encoded genes were 2 and 12, respectively. Differences in promoters and transcriptional starts for the respective plasmid-encoded genes were noted and contribute to increases observed in overall expression. Finally, β-lactam MICs were increased two- to 16-fold when blaACT-1 was expressed in Escherichia coli AmpD– strains compared with E. coli AmpD+ strains. In conclusion, high-level expression of plasmid-encoded ampC genes requires interplay between multiple factors including genetic organization, promoter modifications, genetic background, and to some extent gene copy number. In addition, clinical laboratories need to be aware that genetic backgrounds of inducible plasmid-encoded genes can dramatically influence MICs for organisms not normally associated with derepressed phenotypes.</description><identifier>ISSN: 0305-7453</identifier><identifier>ISSN: 1460-2091</identifier><identifier>EISSN: 1460-2091</identifier><identifier>DOI: 10.1093/jac/dkg204</identifier><identifier>PMID: 12697654</identifier><identifier>CODEN: JACHDX</identifier><language>eng</language><publisher>Oxford: Oxford University Press</publisher><subject>AmpC expression ; ampC gene ; Anti-Bacterial Agents - pharmacology ; Antibacterial agents ; Antibiotics. Antiinfectious agents. Antiparasitic agents ; Bacteriology ; beta-Lactamases - metabolism ; Biological and medical sciences ; Chromosomes, Bacterial - genetics ; Cloning, Molecular ; copy number ; derepressed ; Drug Resistance, Bacterial ; Enterobacter - enzymology ; Enterobacter - genetics ; Enterobacter cloacae ; Enterobacter cloacae - genetics ; Fundamental and applied biological sciences. Psychology ; Gene Expression Regulation, Bacterial - genetics ; Genes, Bacterial - genetics ; Genetics ; Gram-Negative Bacteria - drug effects ; Gram-Negative Bacteria - enzymology ; Klebsiella pneumoniae - genetics ; Medical sciences ; Microbial Sensitivity Tests ; Microbiology ; Pharmacology. Drug treatments ; plasmid-encoded ; Plasmids - genetics ; Promoter Regions, Genetic - genetics ; resistance ; Reverse Transcriptase Polymerase Chain Reaction</subject><ispartof>Journal of antimicrobial chemotherapy, 2003-05, Vol.51 (5), p.1141-1151</ispartof><rights>2003 INIST-CNRS</rights><rights>Copyright Oxford University Press(England) May 2003</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c445t-78033fdcbdd57c4b965a2a83518c7518bef5ea17cd419ebb090cd3d759dbc6cf3</citedby></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27924,27925</link.rule.ids><backlink>$$Uhttp://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=14919425$$DView record in Pascal Francis$$Hfree_for_read</backlink><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/12697654$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Reisbig, Mark D.</creatorcontrib><creatorcontrib>Hossain, Ashfaque</creatorcontrib><creatorcontrib>Hanson, Nancy D.</creatorcontrib><title>Factors influencing gene expression and resistance for Gram-negative organisms expressing plasmid-encoded ampC genes of Enterobacter origin</title><title>Journal of antimicrobial chemotherapy</title><addtitle>J. Antimicrob. Chemother</addtitle><description>High-level expression of AmpC β-lactamases results in organisms resistant to multiple β-lactam antibiotics. The mechanism of chromosomally mediated AmpC resistance has been elucidated, however the mechanism(s) driving plasmid-encoded AmpC resistance are unknown. Studies were designed to identify factors which influence expression of plasmid-encoded ampC genes and correlate these factors with resistance. As the model system, ampC genes of Enterobacter origin were used to determine how gene copy number, genetic background and genetic organization influenced resistance phenotypes. To this end, gene expression from the plasmid-encoded inducible blaACT-1 and non-inducible blaMIR-1 were compared with chromosomal ampC gene expression from both wild-type (WT) and derepressed Enterobacter cloacae isolates. RNA levels within the original clinical isolates were examined using primer extension analysis, whereas a new PCR strategy was developed to examine gene copy number. These data revealed that blaACT-1 and blaMIR-1 constitutive expression was 33- and 95-fold higher than WT expression, whereas copy numbers of the plasmid-encoded genes were 2 and 12, respectively. Differences in promoters and transcriptional starts for the respective plasmid-encoded genes were noted and contribute to increases observed in overall expression. Finally, β-lactam MICs were increased two- to 16-fold when blaACT-1 was expressed in Escherichia coli AmpD– strains compared with E. coli AmpD+ strains. In conclusion, high-level expression of plasmid-encoded ampC genes requires interplay between multiple factors including genetic organization, promoter modifications, genetic background, and to some extent gene copy number. In addition, clinical laboratories need to be aware that genetic backgrounds of inducible plasmid-encoded genes can dramatically influence MICs for organisms not normally associated with derepressed phenotypes.</description><subject>AmpC expression</subject><subject>ampC gene</subject><subject>Anti-Bacterial Agents - pharmacology</subject><subject>Antibacterial agents</subject><subject>Antibiotics. Antiinfectious agents. Antiparasitic agents</subject><subject>Bacteriology</subject><subject>beta-Lactamases - metabolism</subject><subject>Biological and medical sciences</subject><subject>Chromosomes, Bacterial - genetics</subject><subject>Cloning, Molecular</subject><subject>copy number</subject><subject>derepressed</subject><subject>Drug Resistance, Bacterial</subject><subject>Enterobacter - enzymology</subject><subject>Enterobacter - genetics</subject><subject>Enterobacter cloacae</subject><subject>Enterobacter cloacae - genetics</subject><subject>Fundamental and applied biological sciences. Psychology</subject><subject>Gene Expression Regulation, Bacterial - genetics</subject><subject>Genes, Bacterial - genetics</subject><subject>Genetics</subject><subject>Gram-Negative Bacteria - drug effects</subject><subject>Gram-Negative Bacteria - enzymology</subject><subject>Klebsiella pneumoniae - genetics</subject><subject>Medical sciences</subject><subject>Microbial Sensitivity Tests</subject><subject>Microbiology</subject><subject>Pharmacology. Drug treatments</subject><subject>plasmid-encoded</subject><subject>Plasmids - genetics</subject><subject>Promoter Regions, Genetic - genetics</subject><subject>resistance</subject><subject>Reverse Transcriptase Polymerase Chain Reaction</subject><issn>0305-7453</issn><issn>1460-2091</issn><issn>1460-2091</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2003</creationdate><recordtype>article</recordtype><recordid>eNqF0cFqHCEcBnApLc027aUPUKTQHgrT6KjjeAxLNikEekkh5CKO_mdwM6NTnSnpM_Sla7tLAr30ooI_P5UPobeUfKZEsbO9sWfufqgJf4Y2lDekqomiz9GGMCIqyQU7Qa9y3hNCGtG0L9EJrRslG8E36NfO2CWmjH3oxxWC9WHAAwTA8DAnyNnHgE1wuKx9XkywgPuY8GUyUxVgMIv_ATimwQSfp_x4qqTMo8mTd1UJjQ4cNtO8_RudcezxRVggxa7cDqmc94MPr9GL3owZ3hznU_Rtd3Gzvaquv15-2Z5fV5ZzsVSyJYz1znbOCWl5pxphatMyQVsry9BBL8BQaR2nCrqOKGIdc1Io19nG9uwUfTzkzil-XyEvevLZwjiaAHHNWrK6Fm3b_hfSVnGuFCvw_T9wH9cUyid0TWXTSEZlQZ8OyKaYc4Jez8lPJv3UlOg_RepSpD4UWfC7Y-LaTeCe6LG5Aj4cgcnWjH0q1fj85LiiiteiuOrgSnvw8Lhv0r0uz5JCX93eaXZLdjesudOc_Qa7bLkV</recordid><startdate>20030501</startdate><enddate>20030501</enddate><creator>Reisbig, Mark D.</creator><creator>Hossain, Ashfaque</creator><creator>Hanson, Nancy D.</creator><general>Oxford University Press</general><general>Oxford Publishing Limited (England)</general><scope>BSCLL</scope><scope>IQODW</scope><scope>CGR</scope><scope>CUY</scope><scope>CVF</scope><scope>ECM</scope><scope>EIF</scope><scope>NPM</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7QL</scope><scope>7QO</scope><scope>7T7</scope><scope>7U7</scope><scope>7U9</scope><scope>8FD</scope><scope>C1K</scope><scope>FR3</scope><scope>H94</scope><scope>K9.</scope><scope>M7N</scope><scope>NAPCQ</scope><scope>P64</scope><scope>7X8</scope></search><sort><creationdate>20030501</creationdate><title>Factors influencing gene expression and resistance for Gram-negative organisms expressing plasmid-encoded ampC genes of Enterobacter origin</title><author>Reisbig, Mark D. ; Hossain, Ashfaque ; Hanson, Nancy D.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c445t-78033fdcbdd57c4b965a2a83518c7518bef5ea17cd419ebb090cd3d759dbc6cf3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2003</creationdate><topic>AmpC expression</topic><topic>ampC gene</topic><topic>Anti-Bacterial Agents - pharmacology</topic><topic>Antibacterial agents</topic><topic>Antibiotics. Antiinfectious agents. Antiparasitic agents</topic><topic>Bacteriology</topic><topic>beta-Lactamases - metabolism</topic><topic>Biological and medical sciences</topic><topic>Chromosomes, Bacterial - genetics</topic><topic>Cloning, Molecular</topic><topic>copy number</topic><topic>derepressed</topic><topic>Drug Resistance, Bacterial</topic><topic>Enterobacter - enzymology</topic><topic>Enterobacter - genetics</topic><topic>Enterobacter cloacae</topic><topic>Enterobacter cloacae - genetics</topic><topic>Fundamental and applied biological sciences. Psychology</topic><topic>Gene Expression Regulation, Bacterial - genetics</topic><topic>Genes, Bacterial - genetics</topic><topic>Genetics</topic><topic>Gram-Negative Bacteria - drug effects</topic><topic>Gram-Negative Bacteria - enzymology</topic><topic>Klebsiella pneumoniae - genetics</topic><topic>Medical sciences</topic><topic>Microbial Sensitivity Tests</topic><topic>Microbiology</topic><topic>Pharmacology. Drug treatments</topic><topic>plasmid-encoded</topic><topic>Plasmids - genetics</topic><topic>Promoter Regions, Genetic - genetics</topic><topic>resistance</topic><topic>Reverse Transcriptase Polymerase Chain Reaction</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Reisbig, Mark D.</creatorcontrib><creatorcontrib>Hossain, Ashfaque</creatorcontrib><creatorcontrib>Hanson, Nancy D.</creatorcontrib><collection>Istex</collection><collection>Pascal-Francis</collection><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>CrossRef</collection><collection>Bacteriology Abstracts (Microbiology B)</collection><collection>Biotechnology Research Abstracts</collection><collection>Industrial and Applied Microbiology Abstracts (Microbiology A)</collection><collection>Toxicology Abstracts</collection><collection>Virology and AIDS Abstracts</collection><collection>Technology Research Database</collection><collection>Environmental Sciences and Pollution Management</collection><collection>Engineering Research Database</collection><collection>AIDS and Cancer Research Abstracts</collection><collection>ProQuest Health & Medical Complete (Alumni)</collection><collection>Algology Mycology and Protozoology Abstracts (Microbiology C)</collection><collection>Nursing & Allied Health Premium</collection><collection>Biotechnology and BioEngineering Abstracts</collection><collection>MEDLINE - Academic</collection><jtitle>Journal of antimicrobial chemotherapy</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Reisbig, Mark D.</au><au>Hossain, Ashfaque</au><au>Hanson, Nancy D.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Factors influencing gene expression and resistance for Gram-negative organisms expressing plasmid-encoded ampC genes of Enterobacter origin</atitle><jtitle>Journal of antimicrobial chemotherapy</jtitle><addtitle>J. Antimicrob. Chemother</addtitle><date>2003-05-01</date><risdate>2003</risdate><volume>51</volume><issue>5</issue><spage>1141</spage><epage>1151</epage><pages>1141-1151</pages><issn>0305-7453</issn><issn>1460-2091</issn><eissn>1460-2091</eissn><coden>JACHDX</coden><abstract>High-level expression of AmpC β-lactamases results in organisms resistant to multiple β-lactam antibiotics. The mechanism of chromosomally mediated AmpC resistance has been elucidated, however the mechanism(s) driving plasmid-encoded AmpC resistance are unknown. Studies were designed to identify factors which influence expression of plasmid-encoded ampC genes and correlate these factors with resistance. As the model system, ampC genes of Enterobacter origin were used to determine how gene copy number, genetic background and genetic organization influenced resistance phenotypes. To this end, gene expression from the plasmid-encoded inducible blaACT-1 and non-inducible blaMIR-1 were compared with chromosomal ampC gene expression from both wild-type (WT) and derepressed Enterobacter cloacae isolates. RNA levels within the original clinical isolates were examined using primer extension analysis, whereas a new PCR strategy was developed to examine gene copy number. These data revealed that blaACT-1 and blaMIR-1 constitutive expression was 33- and 95-fold higher than WT expression, whereas copy numbers of the plasmid-encoded genes were 2 and 12, respectively. Differences in promoters and transcriptional starts for the respective plasmid-encoded genes were noted and contribute to increases observed in overall expression. Finally, β-lactam MICs were increased two- to 16-fold when blaACT-1 was expressed in Escherichia coli AmpD– strains compared with E. coli AmpD+ strains. In conclusion, high-level expression of plasmid-encoded ampC genes requires interplay between multiple factors including genetic organization, promoter modifications, genetic background, and to some extent gene copy number. In addition, clinical laboratories need to be aware that genetic backgrounds of inducible plasmid-encoded genes can dramatically influence MICs for organisms not normally associated with derepressed phenotypes.</abstract><cop>Oxford</cop><pub>Oxford University Press</pub><pmid>12697654</pmid><doi>10.1093/jac/dkg204</doi><tpages>11</tpages><oa>free_for_read</oa></addata></record> |
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subjects | AmpC expression ampC gene Anti-Bacterial Agents - pharmacology Antibacterial agents Antibiotics. Antiinfectious agents. Antiparasitic agents Bacteriology beta-Lactamases - metabolism Biological and medical sciences Chromosomes, Bacterial - genetics Cloning, Molecular copy number derepressed Drug Resistance, Bacterial Enterobacter - enzymology Enterobacter - genetics Enterobacter cloacae Enterobacter cloacae - genetics Fundamental and applied biological sciences. Psychology Gene Expression Regulation, Bacterial - genetics Genes, Bacterial - genetics Genetics Gram-Negative Bacteria - drug effects Gram-Negative Bacteria - enzymology Klebsiella pneumoniae - genetics Medical sciences Microbial Sensitivity Tests Microbiology Pharmacology. Drug treatments plasmid-encoded Plasmids - genetics Promoter Regions, Genetic - genetics resistance Reverse Transcriptase Polymerase Chain Reaction |
title | Factors influencing gene expression and resistance for Gram-negative organisms expressing plasmid-encoded ampC genes of Enterobacter origin |
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