Perlin M H, Lerner S A
Antimicrob Agents Chemother. 1979 Nov;16(5):598-604. doi: 10.1128/AAC.16.5.598.
Enzymatic phosphorylation of amikacin has not been reported previously in gram-negative bacteria. We found that extracts of MP1, a mutant of Escherichia coli JR66/W677 that is resistant to amikacin, were able to phosphorylate this aminoglycoside more rapidly than were extracts of the parental strain. Conjugal transfer of resistance from MP1 to a recipient strain was accompanied by acquisition in the transconjugants of amikacin phosphotransferase activity and of a 57-megadalton plasmid present in the donor. Partial purification of the phosphotransferase activity on amikacin-Sepharose 4B yielded an enzyme with a substrate spectrum similar to that of the 3'-neomycin-kanamycin phosphotransferase II found E. coli, except that it was also active against amikacin. A mutant of MP1, MP5, had increased susceptibility to amikacin and reduced phosphotransferase activity. MP9, a mutant MP5, was more resistant to amikacin and had increased phosphotransferase activity. The mutations leading to these alterations of amikacin susceptibility and amikacin phosphotransferase activity were transferable with the same plasmid that was associated with amikacin resistance and phosphotransferase activity in MP1. These studies demonstrate that resistance to amikacin in a laboratory strain of E. coli is due to an aminoglycoside phosphotransferase coded by a transferable plasmid-borne gene.
此前尚未有革兰氏阴性菌中阿米卡星发生酶促磷酸化的报道。我们发现，大肠杆菌JR66/W677的耐阿米卡星突变株MP1的提取物能够比亲代菌株的提取物更快地使这种氨基糖苷磷酸化。耐药性从MP1接合转移至受体菌株时，转接合子会获得阿米卡星磷酸转移酶活性以及供体中存在的一个57兆道尔顿的质粒。利用阿米卡星-琼脂糖4B对磷酸转移酶活性进行部分纯化，得到了一种酶，其底物谱与在大肠杆菌中发现的3'-新霉素-卡那霉素磷酸转移酶II相似，只是它对阿米卡星也有活性。MP1的一个突变株MP5对阿米卡星的敏感性增加，磷酸转移酶活性降低。MP9是MP5的一个突变株，对阿米卡星更耐药，且磷酸转移酶活性增加。导致阿米卡星敏感性和阿米卡星磷酸转移酶活性发生这些改变的突变可通过与MP1中阿米卡星耐药性和磷酸转移酶活性相关的同一质粒进行转移。这些研究表明，大肠杆菌实验室菌株对阿米卡星的耐药性是由一个可转移的质粒携带基因编码的氨基糖苷磷酸转移酶所致。
