Identification and Characterization of a Novel aac(6')-Iag Associated with the blaIMP-1 -Integron in a Multidrug-Resistant Pseudomonas aeruginosa

多剤耐性緑膿菌のblaIMP-1インテグロンに存在する新規アミノグリコシドアセチルトランスフェラーゼAAC(6’)-Iagの同定と解析

Kobayashi Kanao

In a continuing study from Dec 2006 to Apr 2008, we characterized nine multi-drug resistant Pseudomonas aeruginosa strains isolated from four patients in a ward at the Hiroshima University Hospital, Japan. Pulsed-field gel electrophoresis of SpeI-digested genomic DNAs from the isolates suggested the clonal expansion of a single strain; however, only one strain, NK0009, was found to produce metallo-β-lactamase. PCR and subsequent sequencing analysis indicated NK0009 possessed a novel class 1 integron, designated as In124, that carries an array of four gene cassettes: a novel aminoglycoside (AG) resistance gene, aac(6')-Iag, blaIMP-1, a truncated form of blaIMP-1, and a truncated form of aac(6')-Iag. The aac(6')-Iag encoded a 167-amino-acid protein that shows 40% identity with AAC(6')-Iz. Recombinant AAC(6')-Iag protein showed aminoglycoside 6'-N-acetyltransferase activity using thin-layer chromatography (TLC) and MS spectrometric analysis. Escherichia coli carrying aac(6')-Iag showed resistance to amikacin, arbekacin, dibekacin, isepamicin, kanamycin, sisomicin, and tobramycin; but not to gentamicin. A conjugation experiment and subsequent Southern hybridization with the gene probes for blaIMP-1 and aac(6')-Ig strongly suggested In124 is on a conjugal plasmid. Transconjugants acquired resistance to gentamicin and were resistant to virtually all AGs, suggesting that the In124 conjugal plasmid also possesses a gene conferring resistance to gentamicin.

Medical sciences [ 490 ]

eng

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[Created] 2014-11-21

Kanao Kobayashi, Ikue Hayashi, Syuntaro Kouda, Fuminori Kato, Tamaki Fujiwara, Shizuo Kayama, Hideki Hirakawa, Hideyuki Itaha, Hiroki Ohge, Naomasa Gotoh, Tsuguru Usui, Akio Matsubara and Motoyuki Sugai; Identification and Characterization of a Novel aac(6')-Iag Associated with the blaIMP-1-Integron in a Multidrug-Resistant Pseudomonas aeruginosa; PLoS ONE 8(8): e70557. (doi: 10.1371/journal.pone.0070557) references

[DOI] http://dx.doi.org/10.1371/journal.pone.0070557 references

広島大学