High level kanamycin resistance associated with the hyperproduction of AAC(3)II and a generalised reduction in the accumulation of aminoglycosides in Acinetobacter spp.

The clinical isolate of Acinetobacter baumannii strain SAK contains an actively transcribed aacC2 gene and a latent aadB gene that encode the aminoglycoside-modifying enzymes, AAC(3)II and AAD(2"), respectively. In an attempt to activate the aadB gene, the strain was cultured in the presence of kanamycin which is a substrate for AAD(2"). Although it was possible to isolate kanamycin resistant derivatives these were not associated with detectable AAD(2") activity. Instead, there was a marked increase in the level of AAC(3)II activity which was associated with amplification of the aacC2 gene.