Bacteremia Caused by a Putative Novel Species in the Genus Erwinia: A Case Report and Genomic Analysis

We report a case of catheter-associated bloodstream infection caused by a putative novel species in the genus <i>Erwinia</i>, identified using whole-genome sequencing (WGS). A female adolescent receiving long-term home parenteral nutrition via a central venous catheter (CVC) presented with a fever. Gram-negative rods were isolated from two CVC-derived blood culture sets, while peripheral cultures remained negative. Conventional identification methods, including VITEK 2, Phoenix M50, MALDI-TOF MS, and 16S rRNA and <i>rpoB</i> gene sequencing, failed to achieve species-level identification. WGS was performed on the isolate using Illumina MiSeq. Genomic analysis revealed a genome size of 5.39 Mb with 56.8% GC content and high assembly completeness. The highest average nucleotide identity (ANI) was 90.3% with <i>Pantoea coffeiphila</i>, and ≤85% with known <i>Erwinia</i> species, suggesting that it represents a distinct taxon. Phylogenetic analyses placed the isolate within the <i>Erwinia</i> clade but separate from any known species. Antimicrobial susceptibility testing showed broad susceptibility. This case highlights the utility of WGS for the identification of rare or novel organisms not captured by conventional methods and expands the clinical spectrum of <i>Erwinia</i> species. While the criteria for species delineation were met, the phenotypic characterization remains insufficient to formally propose a new species.