Abstract
Plasmid pIP1206 was detected in Escherichia coli strain 1540 during the screening of clinical isolates of Enterobacteriaceae for high-level resistance to aminoglycosides. The sequence of this IncFI conjugative plasmid of ca. 100 kb was partially determined. pIP1206 carried the rmtB gene for a ribosome methyltransferase that was shown to modify the N7 position of nucleotide G1405, located in the A site of 16S rRNA. It also contained the qepA (quinolone efflux pump) gene that encodes a 14-transmembrane-segment putative efflux pump belonging to the major facilitator superfamily of proton-dependent transporters. Disruption of membrane proton potential by the efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone in a transconjugant harboring the qepA gene resulted in elevation of norfloxacin accumulation. The transporter conferred resistance to the hydrophilic quinolones norfloxacin and ciprofloxacin.
MeSH terms
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Amino Acid Motifs
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Amino Acid Sequence
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Aminoglycosides / pharmacology*
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Anti-Bacterial Agents / pharmacology*
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Anti-Infective Agents / metabolism
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Conjugation, Genetic
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Conserved Sequence
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DNA, Bacterial / analysis
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DNA, Bacterial / genetics
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Drug Resistance, Multiple, Bacterial
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Enterobacteriaceae / drug effects
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Enterobacteriaceae / enzymology
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Enterobacteriaceae / isolation & purification
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Escherichia coli / chemistry
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Escherichia coli / metabolism*
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Escherichia coli Proteins / chemistry
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Fluoroquinolones / pharmacology*
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Genes, rRNA
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Methylation
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Methyltransferases / genetics*
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Microbial Sensitivity Tests
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Molecular Sequence Data
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Norfloxacin / metabolism
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Plasmids / genetics
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Sequence Analysis, DNA
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Sequence Homology, Amino Acid
Substances
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Aminoglycosides
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Anti-Bacterial Agents
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Anti-Infective Agents
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DNA, Bacterial
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Escherichia coli Proteins
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Fluoroquinolones
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16S rRNA - m7G methyltransferase
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Methyltransferases
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Norfloxacin