A novel characterised multidrug-resistant Pseudocitrobacter isolated from a patient colonised while admitted to a tertiary teaching hospital

Reports of nosocomial infections typically describe recognised microorganisms. In this study, a novel bacterial species was isolated, based on rectal swab screening for carbapenemases post-admission, then phenotypically and genetically characterised. Determined to be a possible Enterobacterales, whole genome sequencing and phylogenetic analysis confirmed identification as Pseudocitrobacter, a relatively new genus (2013) with three known species. This isolate was found to be distinct from these, with 99.7% 16s rRNA identity to Pseudocitrobacter corydidari; an Asian cockroach-associated species. Given the highly conserved/low variability of 16S rRNA genes in Enterobacteriaceae, average nucleotide identity (ANI) analysis compared the new isolate’s genome with those of 18 Enterobacteriaceae species, including confirmed species of Pseudocitrobacter and unnamed Pseudocitrobacter species in the SILVA database. Of these, Pseudocitrobacter corydidari had the highest ANI at 0.9562.