The Staphylococcus qacH gene product: a new member of the SMR family encoding multidrug resistance.
The prevalence of disinfectant-resistant food-related microorganisms is of concern to the food industry. The Staphylococcus saprophyticus strain ST2H6 isolated from a poultry processing plant contained a 2.4-kb plasmid (p2H6) harbouring qacH, which encodes resistance to disinfectants based on quaternary ammonium compounds. The complete p2H6 nucleotide sequence revealed an open reading frame encoding a putative protein of 107 amino acid residues with strong similarity to members of the small multidrug resistance protein family. QacH also conferred high-level ethidium bromide resistance and low-level proflavine resistance and thus differed phenotypically from the similar proteins Smr and QacG. Fluorimetry indicated that the high-level ethidium bromide resistance was due to improved efflux energised by the proton motive force. Site-directed mutagenesis substituting the Asp-24 residue with Glu-24 had no effect on resistance characteristics. An additional open reading frame on p2H6 encoded a putative protein with similarity to rolling circle replication proteins.
Heir
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MATFORSK, Norwegian Food Research Institute, As, Norway. even.heir@matforsk.no
Sundheim
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Holck
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D000595:Amino Acid Sequence; D000818:Animals; D017920:Antiporters; D001426:Bacterial Proteins; D001483:Base Sequence; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D004202:Disinfectants / Q000494:pharmacology*; D018432:Drug Resistance, Multiple / Q000235:genetics*; D029968:Escherichia coli Proteins; D004996:Ethidium / Q000378:metabolism / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009664:Norway; D010957:Plasmids / Q000235:genetics; D011200:Poultry / Q000382:microbiology; D011370:Proflavine / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013210:Staphylococcus / Q000187:drug effects* / Q000235:genetics
D017920:Antiporters; D001426:Bacterial Proteins; D001548:Benzalkonium Compounds; D002352:Carrier Proteins; D004202:Disinfectants; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C112931:qacH protein, Staphylococcus saprophyticus; C075436:EmrE protein, E coli; D011370:Proflavine; D004996:Ethidium