title: Activation of the cryptic aac(6')-Iy aminoglycoside resistance gene of Salmonella by a chromosomal deletion generating a transcriptional fusion.
abstract: Salmonella enterica subsp. enterica serotype Enteritidis BM4361 and BM4362 were isolated from the same patient. BM4361 was susceptible to aminoglycosides, whereas BM4362 was resistant to tobramycin owing to synthesis of a 6'-N-acetyltransferase type I [AAC(6')-I]. Comparative analysis of nucleotide sequences, pulsed-field gel electrophoresis patterns, and Southern hybridizations indicated that the chromosomal aac(6')-Iy genes for the enzyme in both strains were identical and that BM4362 derived from BM4361 following a ca. 60-kb deletion that occurred 1.5 kb upstream from the resistance gene. Northern hybridizations showed that aac(6')-Iy was silent in BM4361 and highly expressed in BM4362 due to a transcriptional fusion. Primer extension mapping identified the transcriptional start site for aac(6')-Iy in BM4362: 5 bp downstream from the promoter of the nmpC gene. Study of the distribution of aac(6')-Iy by PCR and Southern hybridization with a specific probe indicated that the gene, although not found in S. enterica subsp. arizonae, was specific for Salmonella. In this bacterial genus, aac(6')-Iy was located downstream from a cluster of seven open reading frames analogous to an Escherichia coli locus that encodes enzymes putatively involved in carbohydrate transport or metabolism. This genomic environment suggests a role in the catabolism of a specific sugar for AAC(6')-Iy in Salmonella.
authors.affiliation: Unité des Agents Antibactériens, Institut Pasteur, Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Magnet
authors.forename: P
authors.initials: P
authors.lastname: Courvalin
authors.forename: T
authors.initials: T
authors.lastname: Lambert
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D004352:Drug Resistance, Microbial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012480:Salmonella Infections / Q000382:microbiology; D012477:Salmonella enteritidis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D000123:Acetyltransferases; C056532:aminoglycoside N(6')-acetyltransferase