biostudies-literatureButters ABeef Cattle Research Council (BCRC)Beef Cattle Research CouncilCanadian Government | Natural Sciences and Engineering Research Council of Canada (NSERC)Results Driven Agricultural ResearchAlberta Beef ProducersAlberta Beef Producers (ABP)Canadian Government | Natural Sciences and Engineering Research Council of Canadae0053224https://www.ebi.ac.uk/biostudies/studies/S-EPMC11451601biostudies-literatureUnknown12(10)Colistin resistance in <i>Escherichia coli</i> is of public health significance for its use to treat multidrug-resistant Gram-negative infections. Amino acid variations in PmrB have been implicated in colistin resistance in <i>E. coli</i>. In this cross-sectional study, 288 generic <i>E. coli</i> isolates from surveillance of broiler chicken and feedlot cattle feces, retail meat, wastewater, and well water were whole-genome sequenced. Phylogroup designation and screening for two amino acid substitutions in PmrB putatively linked to colistin resistance (Y358N, E123D) were performed <i>in silico</i>. Three additional data sets of publicly available <i>E. coli</i> assemblies were similarly scrutinized: (i) <i>E. coli</i> isolates from studies identifying the Y358N or E123D substitutions, (ii)Microbiology spectrumPmrB Y358N, E123D amino acid substitutions are not associated with colistin resistance but with phylogeny in <i>Escherichia coli</i>.PMC11451601RGPIN/05307-2019ANH.29.202021R098R2021R098RCCheckley SLLiljebjelke KButters AJovel JWaldner CGow SfalsePmrB Y358N, E123D amino acid substitutions are not associated with colistin resistance but with phylogeny in <i>Escherichia coli</i>.Colistin resistance in <i>Escherichia coli</i> is of public health significance for its use to treat multidrug-resistant Gram-negative infections. Amino acid variations in PmrB have been implicated in colistin resistance in <i>E. coli</i>. In this cross-sectional study, 288 generic <i>E. coli</i> isolates from surveillance of broiler chicken and feedlot cattle feces, retail meat, wastewater, and well water were whole-genome sequenced. Phylogroup designation and screening for two amino acid substitutions in PmrB putatively linked to colistin resistance (Y358N, E123D) were performed <i>in silico</i>. Three additional data sets of publicly available <i>E. coli</i> assemblies were similarly scrutinized: (i) <i>E. coli</i> isolates from studies identifying the Y358N or E123D substitutions, (ii)2024-01-01T00:00:00Z2024 Oct2026-06-08T03:31:24.137Z2025-04-04T00:34:04.761ZS-EPMC114516013916250110.1128/spectrum.00532-24