期刊
JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY
卷 70, 期 5, 页码 1331-1337出版社
OXFORD UNIV PRESS
DOI: 10.1093/jac/dku537
关键词
amikacin resistance; S. marcescens; antibiotic resistance genes
资金
- Japanese Ministry of Health, Labour and Welfare [H24-Shinkou-Ippan-010]
- Daiko Foundation
- Association for Research on Lactic Acid Bacteria
- Public Trust Ueda Memorial Infection and Chemotherapy Research Fund
- Grants-in-Aid for Scientific Research [24790551] Funding Source: KAKEN
Objectives: Enterobacteriaceae clinical isolates showing amikacin resistance (MIC 64 to >256 mg/L) in the absence of 16S rRNA methyltransferase (MTase) genes were found. The aim of this study was to clarify the molecular mechanisms underlying amikacin resistance in Enterobacteriaceae clinical isolates that do not produce 16S rRNA MTases. Methods: PCR was performed to detect already-known amikacin resistance determinants. Cloning experiments and sequence analyses were performed to characterize unknown amikacin resistance determinants. Transfer of amikacin resistance determinants was performed by conjugation and transformation. The complete nucleotide sequence of the plasmids was determined by next-generation sequencing technology. Amikacin resistance enzymes were purified with a column chromatography system. The enzymatic function of the purified protein was investigated by thin-layer chromatography (TLC) and HPLC. Results: Among the 14 isolates, 9 were found to carry already-known amikacin resistance determinants such as aac(6')-Ia and aac(6')-Ib. Genetic analyses revealed the presence of a new amikacin acetyltransferase gene, named aac(6')-Ian, located on a 169829 bp transferable plasmid (p11663) of the Serratia marcescens strain NUBL-11663, one of the five strains negative for known aac(6') genes by PCR. Plasmid p11663 also carried a novel ESBL gene, named bla(TLA-3). HPLC and TLC analyses demonstrated that AAC(6')-Ian catalysed the transfer of an acetyl group from acetyl coenzyme A onto an amine at the 6'-position of various aminoglycosides. Conclusions: We identified aac(6')-Ian as a novel amikacin resistance determinant together with a new ESBL gene, bla(TLA-3), on a transferable plasmid of a S. marcescens clinical isolate.
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