Fluoroquinolone-modifying enzyme: a new adaptation of a common aminoglycoside acetyltransferase Ari Robicsek, Jacob Strahilevitz, George A Jacoby Nature Medicine 12, 1,January (2006) Infection disease 林建州 報告

Background Peperazinyl substituent

Identification of a variant of an aminoglycoside-modifying enzyme, that has acquired the ability also to modify select fluoroquinolones AIM

Result Identification of the resistance gene Gene cloning and screening Site –directed mutagenesis Chemical deternination of the mechanism of resistance Phenotypic testing Determination of resistance-promoting potential Population screening

Integron sequence of plasmid pHSH10-2. Encoded quinolone resistance gene

4X

Transformation Low level ciprofloxacin resistance

Figure 1. Sequence alignment of eight different aac(6')-Ib variants and aac(6')-Ib-cr. Try102 Arg, Asp179Try

Figure 2. Enzyme kinetics of AAC(6')-Ib-cr. Ecoli DH10B Acetyl transferase activity

Figure 3. Mutant prevention concentration (MPC) assay. E. coli J53 (o ) E. coli J53 pBC SK-aac(6')-Ib-cr (. )

We describe reduced susceptibility to ciprofloxacin in clinical bacterial isolates conferred by a variant of the gene encoding aminoglycoside acetyltransferase AAC(6')-Ib. This enzyme reduces the activity of ciprofloxacin by N-acetylation at the amino nitrogen on its piperazinyl substituent a single-function resistance enzyme has crossed class boundaries, and is now capable of enzymatically undermining two unrelated antimicrobial agents, one of them fully synthetic. Summary