RT Journal Article SR Electronic T1 Multifactorial Chromosomal Variants Regulate Polymyxin Resistance in Extensively Drug-Resistant Klebsiella pneumoniae JF bioRxiv FD Cold Spring Harbor Laboratory SP 134684 DO 10.1101/134684 A1 Miranda E Pitt A1 Alysha G Elliott A1 Minh Duc Cao A1 Devika Ganesamoorthy A1 Ilias Karaiskos A1 Helen Giamarellou A1 Cely S Abboud A1 Mark AT Blaskovich A1 Matthew A Cooper A1 Lachlan Coin YR 2017 UL http://biorxiv.org/content/early/2017/05/08/134684.abstract AB Objectives Infections facilitated by extensively drug-resistant Klebsiella pneumoniae (XDR-KP) cause high mortality and are disseminating globally. Identifying the genetic basis underpinning resistance allows for rapid diagnosis and treatment.Methods XDR isolates sourced from Greece and Brazil, including nineteen polymyxin-resistant and five polymyxin-susceptible strains, underwent whole genome sequencing.Results Approximately 90% of polymyxin resistance was enabled by alterations upstream or within mgrB. The most common mutation identified was an insertion at nucleotide position 75 in mgrB via an ISKpn26-like element in the ST258 lineage and ISKpn13 in one ST11 isolate. Three strains acquired an IS1 element upstream of mgrB and another strain had an ISKpn25 insertion at 133 bp. Other isolates had truncations (C28STOP, Q30STOP) or a missense mutation (D31E) affecting mgrB. Complementation assays revealed all mgrB perturbations contributed to resistance. Missense mutations in phoQ (T281M, G385C) were also found to facilitate resistance. Several variants in phoPQ co-segregating with the ISKpn26-like insertion were identified as partial suppressor mutations. Three ST258 samples were found to contain subpopulations with different resistance conferring mutations, including the ISKpn26-like insertion colonising with a novel mutation in pmrB (P158R), both confirmed via complementation assays. We also characterized a new multi-drug resistant Klebsiella quasipneumoniae strain ST2401 which was susceptible to polymyxins.Conclusions These findings highlight the broad spectrum of chromosomal modifications which can facilitate and regulate resistance against polymyxins in KP.