Complete Genome Sequencing and Comparative Analysis of Citrobacter koseri CKNJ, a Strain Isolated from a Patient with Endogenous Endophthalmitis

Citrobacter koseri (C. koseri) is an opportunistic pathogen that can cause a variety of diseases. Although the mortality rate of C. koseri infections is high, there is a paucity of clinical information. Furthermore, the genomic features of this species are poorly understood. Herein, we present a patient with endogenous endophthalmitis secondary to septicemia, and collected a C. koseri isolate, CKNJ, from the blood of the patient. Whole genome sequencing revealed that CKNJ harbors no plasmids and codes for 67 putative virulence factors. Whole genome single nucleotide polymorphism-based phylogenetic analysis revealed that the CKNJ strain was close to strains with the same isolation sites. Compared to the other sequenced C. koseri chromosomes, CKNJ contains several strain-variable regions, including one prophage and 2 large genomic islands. Sequencing of the first complete genome of a clinical strain from China should reinforce our understanding of the genomic features and pathogenicity of this invasive infection-causing C. koseri with clinical significance.