Heir E, Sundheim G, Holck A L
MATFORSK, Norwegian Food Research Institute, As, Norway.
J Appl Microbiol. 1999 Mar;86(3):378-88. doi: 10.1046/j.1365-2672.1999.00672.x.
The 2.3 kb resistance plasmid pST94 revealed a new gene (qacG) encoding resistance to benzalkonium chloride (BC), a commonly used quaternary ammonium disinfectant, and the intercalating dye ethidium bromide (Eb) in staphylococci isolated from the food industry. The 107 amino acid QacG protein showing 69.2% identity to the staphylococcal multi-drug resistance protein Smr is a new member of the small multi-drug resistance (SMR) protein family. QacG conferred resistance via proton dependent efflux. An additional ORF on pST94 encoded a protein with extensive similarity to replication proteins of other Gram-positive bacteria. Gene constructs containing the qacG and smr gene region combined with the smr or qacG promoter, respectively, indicated that QacG is more efficient than Smr and that qacG has a weaker promoter. Resistant qacG-containing cells could be adapted to withstand higher concentrations of BC. Adapted qacG-containing cells showed increased resistance mainly to BC. In contrast, adaptation of sensitive cells showed cross-resistance development to a range of compounds. Induction of proton-dependent efflux was observed for BC-adapted staphylococci cells not containing qacG. The ability of sublethal concentrations of BC to develop cross-resistance and induce efflux mechanisms could be of practical significance; it should be considered before use of any new disinfectant and in the design of better disinfection procedures.
2.3 kb的耐药质粒pST94在从食品工业分离出的葡萄球菌中，揭示了一个新基因（qacG），该基因编码对常用季铵消毒剂苯扎氯铵（BC）以及嵌入染料溴化乙锭（Eb）的耐药性。107个氨基酸的QacG蛋白与葡萄球菌多药耐药蛋白Smr的同一性为69.2%，是小多药耐药（SMR）蛋白家族的新成员。QacG通过质子依赖性外排赋予耐药性。pST94上的另一个开放阅读框编码一种与其他革兰氏阳性菌复制蛋白具有广泛相似性的蛋白。分别包含qacG和smr基因区域并与smr或qacG启动子结合的基因构建体表明，QacG比Smr更有效，且qacG有一个较弱的启动子。含有耐药qacG的细胞可以适应耐受更高浓度的BC。适应后的含qacG细胞主要表现出对BC的耐药性增加。相比之下，敏感细胞的适应表现出对一系列化合物的交叉耐药性发展。在不含qacG的BC适应葡萄球菌细胞中观察到质子依赖性外排的诱导。亚致死浓度的BC产生交叉耐药性和诱导外排机制的能力可能具有实际意义；在使用任何新消毒剂之前以及在设计更好的消毒程序时都应予以考虑。
