Tsai S F, Zervos M J, Clewell D B, Donabedian S M, Sahm D F, Chow J W
Research and Medical Service, Department of Veterans' Affairs Medical Center, Detroit, Michigan 48201, USA.
Antimicrob Agents Chemother. 1998 May;42(5):1229-32. doi: 10.1128/AAC.42.5.1229.
Enterococcus casseliflavus UC73 is a clinical blood isolate with high-level resistance to gentamicin. DNA preparations from UC73 failed to hybridize with intragenic probes for aac(6')-Ie-aph(2'')-Ia and aph(2'')-Ic. A 4-kb fragment from UC73 was cloned and found to confer resistance to gentamicin in Escherichia coli DH5alpha transformants. Nucleotide sequence analysis revealed the presence of a 906-bp open reading frame whose deduced amino acid sequence had a region with homology to the aminoglycoside-modifying enzyme APH(2'')-Ic and to the C-terminal domain of the bifunctional enzyme AAC(6')-APH(2''). The gene is designated aph(2'')-Id, and its observed phosphotransferase activity is designated APH(2'')-Id. A PCR-generated intragenic probe hybridized to the genomic DNA from 17 of 118 enterococcal clinical isolates (108 with high-level gentamicin resistance) from five hospitals. All 17 were vancomycin-resistant Enterococcus faecium isolates, and pulsed-field typing revealed three distinct clones. The combination of ampicillin plus either amikacin or neomycin exhibited synergistic killing against E. casseliflavus UC73. Screening and interpretation of high-level aminoglycoside resistance in enterococci may need to be modified to include detection of APH(2'')-Id.
卡氏肠球菌UC73是一株对庆大霉素具有高水平耐药性的临床血液分离株。来自UC73的DNA制剂未能与针对aac(6')-Ie-aph(2'')-Ia和aph(2'')-Ic的基因内探针杂交。从UC73中克隆出一个4 kb的片段，发现其可使大肠杆菌DH5α转化子对庆大霉素产生耐药性。核苷酸序列分析显示存在一个906 bp的开放阅读框，其推导的氨基酸序列有一个区域与氨基糖苷修饰酶APH(2'')-Ic以及双功能酶AAC(6')-APH(2'')的C末端结构域具有同源性。该基因被命名为aph(2'')-Id，其观察到的磷酸转移酶活性被命名为APH(2'')-Id。一个PCR产生的基因内探针与来自五家医院的118株肠球菌临床分离株（108株对庆大霉素具有高水平耐药性）中的17株的基因组DNA杂交。所有17株均为耐万古霉素屎肠球菌分离株，脉冲场分型显示有三个不同的克隆。氨苄西林加阿米卡星或新霉素的组合对卡氏肠球菌UC73表现出协同杀伤作用。肠球菌中高水平氨基糖苷耐药性的筛查和解释可能需要修改，以包括对APH(2'')-Id的检测。
