Anaïs Potron1,2, Jean-Baptiste Vuillemenot2, Hélène Puja2, Pauline Triponney1, Maxime Bour1, Benoit Valot2, Marlène Amara3, Laurent Cavalié4, Christine Bernard5, Laurence Parmeland6, Florence Reibel7, Gerald Larrouy-Maumus8, Laurent Dortet9,10, Rémy A Bonnin9,10, Patrick Plésiat1,2. 1. French National Reference Centre for Antibiotic Resistance, University Hospital of Besançon, Besançon, France. 2. UMR6249, CNRS Chrono-Environnement, Franche-Comté University, Besançon, France. 3. Hospital of Versailles, Le Chesnay, France. 4. University Hospital of Toulouse, Toulouse, France. 5. Grand Hôpital de l'Est Parisien, Jossigny, France. 6. Saint-Joseph Saint-Luc Hospital, Lyon, France. 7. Groupe Hospitalier Nord Essonne, Longjumeau, France. 8. MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, UK. 9. EA7361 'Structure, Dynamic, Function and Expression of Broad Spectrum β-Lactamases', Paris-Sud University, LabEx Lermit, Faculty of Medicine, Le Kremlin-Bicêtre, France. 10. French National Reference Centre for Antibiotic Resistance, Associate Laboratory, Le Kremlin-Bicêtre, France.
Abstract
BACKGROUND: Colistin resistance in Acinetobacter baumannii often results from mutational activation of the two-component system PmrAB and subsequent addition of phospho-ethanolamine (pEtN) to lipooligosaccharide by up-regulated pEtN transferase PmrC. OBJECTIVES: To characterize mechanisms of colistin resistance independent of PmrCAB in A. baumannii. METHODS: Twenty-seven colistin-resistant A. baumannii were collected from 2012 to 2018. Analysis of operon pmrCAB was performed by PCR and sequencing. Seven strains were investigated further by WGS and whole-genome MLST (wgMLST). RESULTS: Seven out of the 27 selected isolates were found to overexpress eptA, a gene homologous to pmrC, likely as a consequence of upstream insertion of an ISAba1 element. Insertion sites of ISAba1 were mapped 13, 18 and 156 bp ahead of the start codon of eptA in five strains, one strain and one strain, respectively. The finding that the isolates did not cluster together when compared by wgMLST analysis supports the notion that distinct insertion events occurred in close, but different, genetic backgrounds. CONCLUSIONS: Activation of eptA and subsequent addition of pEtN to the cell surface represents a novel mechanism of resistance to colistin in A. baumannii.
BACKGROUND: Colistin resistance in Acinetobacter baumannii often results from mutational activation of the two-component system PmrAB and subsequent addition of phospho-ethanolamine (pEtN) to lipooligosaccharide by up-regulated pEtN transferase PmrC. OBJECTIVES: To characterize mechanisms of colistin resistance independent of PmrCAB in A. baumannii. METHODS: Twenty-seven colistin-resistant A. baumannii were collected from 2012 to 2018. Analysis of operon pmrCAB was performed by PCR and sequencing. Seven strains were investigated further by WGS and whole-genome MLST (wgMLST). RESULTS: Seven out of the 27 selected isolates were found to overexpress eptA, a gene homologous to pmrC, likely as a consequence of upstream insertion of an ISAba1 element. Insertion sites of ISAba1 were mapped 13, 18 and 156 bp ahead of the start codon of eptA in five strains, one strain and one strain, respectively. The finding that the isolates did not cluster together when compared by wgMLST analysis supports the notion that distinct insertion events occurred in close, but different, genetic backgrounds. CONCLUSIONS: Activation of eptA and subsequent addition of pEtN to the cell surface represents a novel mechanism of resistance to colistin in A. baumannii.
Authors: Mattia Palmieri; Marco Maria D'Andrea; Andreu Coello Pelegrin; Nadine Perrot; Caroline Mirande; Bernadette Blanc; Nicholas Legakis; Herman Goossens; Gian Maria Rossolini; Alex van Belkum Journal: Front Microbiol Date: 2020-04-15 Impact factor: 5.640