title: Association of Novel Nonsynonymous Single Nucleotide Polymorphisms in ampD with Cephalosporin Resistance and Phylogenetic Variations in ampC, ampR, ompF, and ompC in Enterobacter cloacae Isolates That Are Highly Resistant to Carbapenems.
abstract: InEnterobacter cloacae, the genetic lesions associated with derepression of the AmpC β-lactamase include diverse single nucleotide polymorphisms (SNPs) and/or indels in theampDandampRgenes and SNPs inampC, while diverse SNPs in the promoter region or SNPs/indels within the coding sequence of outer membrane proteins have been described to alter porin production leading to carbapenem resistance. We sought to define the underlying mechanisms conferring cephalosporin and carbapenem resistance in a collection ofE. cloacaeisolates with unusually high carbapenem resistance and no known carbapenemase and, in contrast to many previous studies, considered the SNPs we detected in relation to the multilocus sequence type (MLST)-based phylogeny of our collection. Whole-genome sequencing was applied on the most resistant isolates to seek novel carbapenemases, expression ofampCwas measured by reverse transcriptase PCR, and porin translation was detected by SDS-PAGE. SNPs occurring inampC,ampR,ompF, andompCgenes (and their promoter regions) were mostly phylogenetic variations, relating to the isolates' sequence types, whereas nonsynonymous SNPs inampDwere associated with derepression of AmpC and cephalosporin resistance. The additional loss of porins resulted in high-level carbapenem resistance, underlining the clinical importance of chromosomal mutations among carbapenem-resistantE. cloacae.
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom b.baboueeflury@bluewin.ch.
authors: Baharak
authors: B
authors: Babouee Flury
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Matthew J
authors: MJ
authors: Ellington
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Katie L
authors: KL
authors: Hopkins
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Jane F
authors: JF
authors: Turton
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Michel
authors: M
authors: Doumith
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Richard
authors: R
authors: Loy
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Peter
authors: P
authors: Staves
authors: Division of Clinical Microbiology, University Hospital Basel, Basel, Switzerland.
authors: Vladimira
authors: V
authors: Hinic
authors: Division of Clinical Microbiology, University Hospital Basel, Basel, Switzerland.
authors: Reno
authors: R
authors: Frei
authors: Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit, Public Health England, London, United Kingdom.
authors: Neil
authors: N
authors: Woodford
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology; D018550:Cephalosporin Resistance / Q000235:genetics; D016972:Enterobacter cloacae / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D006801:Humans; D054643:INDEL Mutation; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D018272:Porins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; C113724:OmpC protein; C109237:OmpF protein; D018272:Porins; C071526:AmpR protein, Bacteria; C062460:AmpD protein, Bacteria; D009238:N-Acetylmuramoyl-L-alanine Amidase; C048795:AmpC beta-lactamases; D001618:beta-Lactamases