AMINOGLYCOSIDE PHOSPHOTRANSFERASE-II-MEDIATED AMIKACIN RESISTANCE IN ESCHERICHIA-COLI
AMINOGLYCOSIDE PHOSPHOTRANSFERASE-II-MEDIATED AMIKACIN RESISTANCE IN ESCHERICHIA-COLI
复制标题
DOI：
10.1128/aac.20.3.344
复制
发表时间：
1981-01-01
影响因子：
4.9
通讯作者：
KAPTIJN, GMP
中科院分区：
文献类型：
--
作者：
BONGAERTS, GPA;KAPTIJN, GMP
大肠选择了具有质粒阿米卡星抗性的大肠杆菌菌株，其证据强烈表明抗性是由氨基糖苷磷酸转移酶[APH（3“）-II]介导的。这种抗性与对卡那霉素和新霉素的抗性相结合。通过磷酸化部分纯化的APH（3“）-II [无APH（3”）]修饰的阿米卡星。APH（3“）-II介导的反应的产物（即，3“-O-磷酰基-阿米卡星）失去抗菌活性。在细胞适应更高浓度的阿米卡星后，阿米卡星修饰的APH（3“）-II活性增加5-10倍。该酶的底物谱显示，与新霉素相比，该酶对阿米卡星的活性较低。有人认为，酶的水平，而不是其底物谱是重要的酶介导的电阻。酶水平的增加与编码APH（3“）-II和APH（3”）活性的110兆道尔顿质粒（pBN 66）拷贝数的增加相关。拷贝数的增加是不可逆的，这种现象归因于影响拷贝数的基因突变。在接合转移体中，存在原始的低拷贝数，因此突变必须位于染色体上而不是质粒上。
An E. coli strain with a plasmidic amikacin resistance was selected for which the evidence strongly indicates that resistance is mediated by aminoglycoside phosphotransferase [APH(3'')-II]. This resistance was coupled with resistance against kanamycin and neomycin. Partially purified APH(3'')-II [APH(3") free] modified amikacin by phosphorylation. The product of the APH(3'')-II mediated reaction (i.e., 3''-O-phosphoryl-amikacin) lost its antibacterial activity. The amikacin-modifying APH(3'')-II activity increased 5-10-fold after adaptation of the cells to higher concentrations of amikacin. The substrate spectrum of this enzyme showed a low activity against amikacin as compared with neomycin. It is argued that the enzyme level rather than its substrate spectrum is important for enzyme-mediated resistance. The increase in enzyme levels was correlated with an increase in copy number of a 110-Megadalton plasmid (pBN66) which coded for the APH(3'')-II and the APH(3") activity. The increase in copy number was irreversible and this phenomenon is ascribed to a mutation of a gene which affects the copy number. In transconjugants, the original low copy number was present and the mutation thus must be located on the chromosome and not on the plasmid.