novel 6'-n-aminoglycoside acetyltransferase AAC(6')-Iaj from a clinical isolate of Pseudomonas aeruginosa.

Pseudomonas aeruginosa NCGM1588 has a novel chromosomal class 1 integron, In151, which includes the aac(6')-Iaj gene. The encoded protein, AAC(6')-Iaj, was found to consist of 184 amino acids, with 70% identity to AAC(6')-Ia. Escherichia coli transformed with a plasmid containing the aac(6')-Iaj gene acquired resistance to all aminoglycosides tested except gentamicin. Of note, aac(6')-Iaj contributed to the resistance to arbekacin. Thin-layer chromatography revealed that AAC(6')-Iaj acetylated all aminoglycosides tested except gentamicin. These findings indicated that AAC(6')-Iaj is a functional acetyltransferase that modifies the amino groups at the 6' positions of aminoglycosides and contributes to aminoglycoside resistance of P. aeruginosa NCGM1588, including arbekacin.