Genomic analysis of antibiotic resistance and virulence factors in the uropathogen <i>Citrobacter koseri</i>

<i>Citrobacter koseri</i> is a significant bacterial cause of community-acquired urinary tract infections in female college students. Given limited previous attention to genomic analysis and molecular epidemiology of this species, whole-genome sequencing was carried out for eight uropathogenic <i>C. koseri</i> clinical isolates. Six complete and two draft assemblies are presented. Genome organization was largely conserved between isolates, and comparative analysis with archived genomes suggests that more than 90% of <i>C. koseri</i> genes are conserved across the species. These isolates contained relatively few mobile genetic elements (plasmids, prophage, transposons and insertion elements) and extensive antiphage defence systems. Other than a single conserved chromosomal β-lactamase gene, little or no acquired antibiotic resistance was observed. Clues to urovirulence were sought among genes conserved in <i>C. koseri</i> but not found in other <i>Citrobacter</i> genomes, suggesting roles for iron acquisition, motility and adhesion.