Characterization of Acinetobacter haemolyticus aac(6')-Ig gene encoding an aminoglycoside 6'-N-acetyltransferase which modifies amikacin

Abstract

The amikacin resistance gene acc(6')-Ig of Acinetobacter haemolyticus BM2685 encoding an aminoglycoside 6'-N-acetyltransferase was characterized. The gene was identified as a coding sequence of 438 bp corresponding to a protein with a calculated mass of 16,522 Da. Analysis of the deduced amino acid sequence suggested that it was the fourth member of a subfamily of aminoglycoside 6'-N-acetyltransferases. The resistance gene was not transferable either by conjugation to Escherichia coli or to Acinetobacter baumannii or by transformation into Acinetobacter calcoaceticus. Plasmid DNA from strain BM2685 did not hybridize with an intragenic aac(6')-Ig probe. These results suggest a chromosomal location for this gene. The gene was detected by DNA hybridization in all 20 strains of A. haemolyticus tested but not in 179 other Acinetobacter strains, including A. baumannii, A. lwoffii, A. junii, and A. johnsonii and genospecies 3, 6, 11, 13, 14, 15, 16, and 17, of which 162 were amikacin resistant. The probe did not hybridize in dot blot assays with DNAs purified from members of the families Enterobacteriaceae and Pseudomonadaceae that encode 6'-N-acetyltransferases. These data suggest that the aac(6')-Ig gene is species specific and may be used to identify A. haemolyticus.

The Ecology, Biology and Pathogenesis of Acinetobacter spp.: An Overview

“…The mechanism by which A. haemolyticus produces this toxin is, however, not well understood. Lambert et al (65) speculated that A. haemolyticus acquires vtx2-producing activity via horizontal gene transfer in the gut lumen, since it can be rapidly transformed. In any case, the pathogenicity, basic structure, and chemical components of the toxins are the same as those of verotoxins from E. coli and other bacteria (65).…”

“…Lambert et al (65) speculated that A. haemolyticus acquires vtx2-producing activity via horizontal gene transfer in the gut lumen, since it can be rapidly transformed. In any case, the pathogenicity, basic structure, and chemical components of the toxins are the same as those of verotoxins from E. coli and other bacteria (65). The emergence of verotoxin-producing A. haemolyticus strains is worrisome given the high transformability of Acinetobacter spp.…”

Identification and Characterization of the Point Mutation Which Affects the Transcription Level of the Chromosomal 3- N -Acetyltransferase Gene of Streptomyces griseus SS-1198

“…The latter case includes genes for aminoglycoside acetyltransferase (AAC) enzymes, for example, the aac(2Ј)-Ia gene of Providencia stuartii (22) (19), the aac(6Ј)-Ii gene of Enterococcus faecium (5), and the aac(6Ј)-Ij gene of Acinetobacter sp. strain 13 (18).…”

Characterization of the chromosomal aac(6')-Ij gene of Acinetobacter sp. 13 and the aac(6')-Ih plasmid gene of Acinetobacter baumannii

“…(25,28), and aac(6')-Ig is part ofA. haemolyticus chromosome (14). We have found Acinetobacter strains that produce AAC(6')-I 'enzymes and do not contain any known aac(6')-I sequence (unpublished data).…”