Eun-Jeong Yoon1, Sylvie Goussard1, Alexandr Nemec2, Thierry Lambert3, Patrice Courvalin4, Catherine Grillot-Courvalin1. 1. Institut Pasteur, Unité des Agents Antibactériens, Paris, France. 2. Laboratory of Bacterial Genetics, National Institute of Public Health, Prague, Czech Republic. 3. EA4043, Faculté de Pharmacie, Université Paris Sud, Châtenay-Malabry, France. 4. Institut Pasteur, Unité des Agents Antibactériens, Paris, France patrice.courvalin@pasteur.fr.
Abstract
OBJECTIVES: The aac(6')-Ih gene encoding aminoglycoside 6'-N-acetyltransferase type I subtype h [AAC(6')-Ih] is plasmid-borne in Acinetobacter baumannii where it confers high-level amikacin resistance, but its origin remains unknown. We searched for the gene in the genomes of a collection of 133 Acinetobacter spp. and studied its species specificity, expression and dissemination. METHODS: Gene copy number was determined by quantitative PCR, expression by quantitative RT-PCR, MIC by microdilution and transfer by plasmid mobilization. RESULTS: The aac(6')-Ih gene was present in the chromosome of the two Acinetobacter gyllenbergii of the collection and was detected in all seven A. gyllenbergii clinical isolates. They had indistinguishable flanking regions indicating that the gene was intrinsic to this species. A. baumannii PIS Aba23 promoters were provided by insertion of ISAba23, which disrupted the Pnative promoter in A. gyllenbergii. Both types of promoters were similarly potent in Escherichia coli and A. baumannii. Aminoglycoside MICs for A. baumannii harbouring pIP1858 were higher than for A. gyllenbergii due to gene dosage. The non-self-transferable plasmid could be mobilized to other A. baumannii cells by the broad host range plasmid RP4. CONCLUSIONS: We have found the origin of aac(6')-Ih in A. gyllenbergii, a species isolated, although rarely, in humans, and documented that dissemination of this gene is restricted to the Acinetobacter genus.
OBJECTIVES: The aac(6')-Ih gene encoding aminoglycoside 6'-N-acetyltransferase type I subtype h [AAC(6')-Ih] is plasmid-borne in Acinetobacter baumannii where it confers high-level amikacin resistance, but its origin remains unknown. We searched for the gene in the genomes of a collection of 133 Acinetobacter spp. and studied its species specificity, expression and dissemination. METHODS: Gene copy number was determined by quantitative PCR, expression by quantitative RT-PCR, MIC by microdilution and transfer by plasmid mobilization. RESULTS: The aac(6')-Ih gene was present in the chromosome of the two Acinetobacter gyllenbergii of the collection and was detected in all seven A. gyllenbergii clinical isolates. They had indistinguishable flanking regions indicating that the gene was intrinsic to this species. A. baumannii PIS Aba23 promoters were provided by insertion of ISAba23, which disrupted the Pnative promoter in A. gyllenbergii. Both types of promoters were similarly potent in Escherichia coli and A. baumannii. Aminoglycoside MICs for A. baumannii harbouring pIP1858 were higher than for A. gyllenbergii due to gene dosage. The non-self-transferable plasmid could be mobilized to other A. baumannii cells by the broad host range plasmid RP4. CONCLUSIONS: We have found the origin of aac(6')-Ih in A. gyllenbergii, a species isolated, although rarely, in humans, and documented that dissemination of this gene is restricted to the Acinetobacter genus.
Authors: Morten O A Sommer; Christian Munck; Rasmus Vendler Toft-Kehler; Dan I Andersson Journal: Nat Rev Microbiol Date: 2017-07-31 Impact factor: 60.633