title: Genetic analysis of new 16S rRNA mutations conferring aminoglycoside resistance in Mycobacterium abscessus.
abstract: OBJECTIVE
  We studied the development and fitness cost of 2-deoxystreptamine aminoglycoside resistance of Mycobacterium abscessus.
  
  
  METHODS
  Spontaneous 2-deoxystreptamine aminoglycoside-resistant mutants were selected and the frequency of their appearance was determined. The 3' part of the rrs gene was sequenced to characterize mutations. Additionally, we determined the MICs of aminoglycoside drugs for the different mutants obtained. The dominance/recessivity traits of the different mutations were examined and we explored the potential cost conferred by the mutations selected in vitro on the fitness of these isolates compared with the wild-type strain.
  
  
  RESULTS
  The in vitro mutation rate for 2-deoxystreptamine aminoglycoside resistance was ∼10(-7) mutations/cell division. In addition to the known rrs A→G substitution at position 1408 (Escherichia coli numbering), which confers kanamycin resistance (Kan(R)), three new substitutions in rrs were identified in M. abscessus Kan(R) mutants, i.e. T→A at 1406, C→T at 1409 and G→T at 1491. Heterodiploids carrying genomic mutations T→A at 1406 and A→G at 1408 with the wild-type rrs gene carried by the pNBV1 vector showed a resistant phenotype. In contrast, heterodiploids carrying genomic mutations C→T at 1409 and G→T at 1491 with the wild-type rrs gene carried by the pNBV1 vector had a susceptible phenotype. No burden on fitness was observed for the different mutations.
  
  
  CONCLUSIONS
  Mutations in the rrs gene that confer high-level 2-deoxystreptamine aminoglycoside resistance on M. abscessus differ in their dominance/recessivity traits and have no biological cost under our experimental conditions.
authors.affiliation: Université Paris Descartes, Faculté de Médecine Paris Descartes, F-75730 Paris Cedex 15, France. rachid.nessar@inserm.fr
authors.forename: Rachid
authors.initials: R
authors.lastname: Nessar
authors.forename: Jean Marc
authors.initials: JM
authors.lastname: Reyrat
authors.forename: Alan
authors.initials: A
authors.lastname: Murray
authors.forename: Brigitte
authors.initials: B
authors.lastname: Gicquel
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli; D005799:Genes, Dominant; D005808:Genes, Recessive; D020459:Genes, rRNA; D006801:Humans; D008826:Microbial Sensitivity Tests; D009161:Mycobacterium / Q000187:drug effects* / Q000235:genetics*; D017354:Point Mutation; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S