biostudies-literatureHarris SDepartment for Environment, Food and Rural AffairsBiotechnology and Biological Sciences Research Council2026https://www.ebi.ac.uk/biostudies/studies/S-EPMC6128206biostudies-literatureUnknown9Bacterial surface polysaccharides play significant roles in fitness and virulence. In Gram-negative bacteria such as <i>Escherichia coli</i>, major surface polysaccharides are lipopolysaccharide (LPS) and capsule, representing O- and K-antigens, respectively. There are multiple combinations of O:K types, many of which are well-characterized and can be related to ecotype or pathotype. In this investigation, we have identified a novel O:K permutation resulting through a process of major genome reorganization in a clade of <i>E. coli</i>. A multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing strain - <i>E. coli</i> 26561 - represented a prototype of strains combining a locus variant of O89 and group 1 capsular polysaccharide. Specifically, the variant O89 locus in this strain Frontiers in microbiologyVariant O89 O-Antigen of <i>E. coli</i> Is Associated With Group 1 Capsule Loci and Multidrug Resistance.PMC6128206OD1718Dobrindt UGoldstone RJHarris SRao FVMadec JYValat CFoster GQi RSmith DGEPiotrowska MJfalseVariant O89 O-Antigen of <i>E. coli</i> Is Associated With Group 1 Capsule Loci and Multidrug Resistance.Bacterial surface polysaccharides play significant roles in fitness and virulence. In Gram-negative bacteria such as <i>Escherichia coli</i>, major surface polysaccharides are lipopolysaccharide (LPS) and capsule, representing O- and K-antigens, respectively. There are multiple combinations of O:K types, many of which are well-characterized and can be related to ecotype or pathotype. In this investigation, we have identified a novel O:K permutation resulting through a process of major genome reorganization in a clade of <i>E. coli</i>. A multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing strain - <i>E. coli</i> 26561 - represented a prototype of strains combining a locus variant of O89 and group 1 capsular polysaccharide. Specifically, the variant O89 locus in this strain 2018-01-01T00:00:00Z20182026-05-04T20:05:01.112Z2019-03-26T23:56:34ZS-EPMC61282063023351710.3389/fmicb.2018.02026