Discovery of a gene conferring multiple-aminoglycoside resistance in Escherichia coli

Abstract

Bovine-origin Escherichia coli isolates were tested for resistance phenotypes using a disk diffusion assay and for resistance genotypes using a DNA microarray. An isolate with gentamicin and amikacin resistance but with no corresponding genes detected yielded a 1,056-bp DNA sequence with the closest homologues for its inferred protein sequence among a family of 16S rRNA methyltransferase enzymes. These enzymes confer high-level aminoglycoside resistance and have only recently been described in Gram-negative bacteria.

FIG. 1.

Phylogenetic relationships among 16S rRNA methyltransferases. Twenty amino acid sequences of known 16S rRNA methyltransferases were compared in CLUSTALW, and the results were illustrated using the TreeViewX program, version 0.5.0 for Macintosh OS X. GenBank or EMBL accession numbers associated with each gene are as follows: RmtA, AB120321; RmtB, AB117036; ArmA, AF550415; RmtC, AB194779; RmtD, DQ914960; RmtE, GU201947; NpmA, AB261016; FmrO, D13171; GrmO, AY524043; Grm, M55521; Sgm, A45282; GrmA, AY524043; Kmr, AB164642; Kan, AJ414669; NbrB, AF038408; KgmB, AAB20100; KamA (FmrT), D13170; KamC, AAA26499; KamB, CAF33037; and Amr, AAB08.