Heir E, Sundheim G, Holck A L
MATFORSK, Norwegian Food Research Institute, As, Norway.
FEMS Microbiol Lett. 1998 Jun 1;163(1):49-56. doi: 10.1111/j.1574-6968.1998.tb13025.x.
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.
耐消毒剂的食品相关微生物的流行情况引起了食品行业的关注。从一家家禽加工厂分离出的腐生葡萄球菌菌株ST2H6含有一个2.4 kb的质粒（p2H6），该质粒携带qacH，它编码对基于季铵化合物的消毒剂的抗性。完整的p2H6核苷酸序列揭示了一个开放阅读框，其编码一个由107个氨基酸残基组成的推定蛋白，该蛋白与小多药抗性蛋白家族的成员具有高度相似性。QacH还赋予了高水平的溴化乙锭抗性和低水平的原黄素抗性，因此在表型上与相似蛋白Smr和QacG不同。荧光测定表明，高水平的溴化乙锭抗性是由于质子动力驱动的外排增强所致。将Asp-24残基替换为Glu-24的定点诱变对抗性特征没有影响。p2H6上的另一个开放阅读框编码一个与滚环复制蛋白相似的推定蛋白。
