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Antimicrobial Agents and Chemotherapy, June 2009, p. 2327-2334, Vol. 53, No. 6
0066-4804/09/$08.00+0     doi:10.1128/AAC.01360-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

AAC(6')-Iaf, a Novel Aminoglycoside 6'-N-Acetyltransferase from Multidrug-Resistant Pseudomonas aeruginosa Clinical Isolates{triangledown}

Tomoe Kitao, Tohru Miyoshi-Akiyama, and Teruo Kirikae*

Department of Infectious Diseases, Research Institute, International Medical Center of Japan, Shinjuku, Tokyo 162-8655, Japan

Received 9 October 2008/ Returned for modification 20 November 2008/ Accepted 29 March 2009

We report here the characterization of a novel aminoglycoside resistance gene, aac(6')-Iaf, present in two multidrug-resistant (MDR) Pseudomonas aeruginosa clinical isolates. These isolates, IMCJ798 and IMCJ799, were independently obtained from two patients, one with a urinary tract infection and the other with a decubitus ulcer, in a hospital located in the western part of Japan. Although the antibiotic resistance profiles of IMCJ798 and IMCJ799 were similar to that of MDR P. aeruginosa IMCJ2.S1, which caused outbreaks in the eastern part of Japan, the pulsed-field gel electrophoresis patterns for these isolates were different from that for IMCJ2.S1. Both IMCJ798 and IMCJ799 were found to contain a novel chromosomal class 1 integron, In123, which included aac(6')-Iaf as the first cassette gene. The encoded protein, AAC(6')-Iaf, was found to consist of 183 amino acids, with 91 and 87% identity to AAC(6')-Iq and AAC(6')-Im, respectively. IMCJ798, IMCJ799, and Escherichia coli transformants carrying a plasmid containing the aac(6')-Iaf gene and its upstream region were highly resistant to amikacin, dibekacin, and kanamycin but not to gentamicin. The production of AAC(6')-Iaf in these strains was confirmed by Western blot analysis. Thin-layer chromatography indicated that AAC(6')-Iaf is a functional acetyltransferase that specifically modifies the amino groups at the 6' positions of aminoglycosides. Collectively, these findings indicate that AAC(6')-Iaf contributes to aminoglycoside resistance.

* Corresponding author. Mailing address: Department of Infectious Diseases, Research Institute, International Medical Center of Japan, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan. Phone: (81) 3 3202 7181, ext. 2838. Fax: (81) 3 3202 7364. E-mail: tkirikae{at}ri.imcj.go.jp

{triangledown} Published ahead of print on 6 April 2009.

Antimicrobial Agents and Chemotherapy, June 2009, p. 2327-2334, Vol. 53, No. 6
0066-4804/09/$08.00+0     doi:10.1128/AAC.01360-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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