Characterization of NDM-4-Producing Citrobacter amalonaticus Isolates from China

Objective: The aim of this study was to investigate the genomic features of carbapenem-resistant Citrobacter spp. carrying blaNDM-4 on a novel IncFII-116 plasmid. Methods: Carbapenem-resistant Citrobacter spp. isolates were collected from diarrheal inpatients. Antibiotic susceptibility testing was routinely performed. Whole-genome sequencing and bioinformatic analyses were conducted on the isolates with blaNDM-4 gene. Results: Whole- genome sequencing was performed on the two C. amalonaticus isolates carrying bla NDM-4. Whole-genome analysis revealed that pL5091_ blaNDM-4 and pL5094_ blaNDM-4 belong to a new type of plasmid (IncFII-116) with lengths of 87124 bp and 87952 bp in two C. amalonaticus, respectively. Moreover, blaNDM-4 was encoded in the trpF-ble-bla NDM-4 -IS15 cassette array. Conclusion: We identified a novel IncFII-116 plasmid carrying blaNDM-4 in C. amalonaticus for the first time, raising concerns about the emergence of carbapenem-resistant Citrobacter spp. Keywords: carbapenem-resistant, C. amalonaticus, IncFII-116, NDM-4, whole-genome sequencing