Genome-Based Retrospective Analysis of a Providencia stuartii Outbreak in Rome, Italy: Broad Spectrum IncC Plasmids Spread the NDM Carbapenemase within the Hospital.

is a member of the family, notorious for its intrinsic resistance to several antibiotics, including last-resort drugs such as colistin and tigecycline. Between February and March 2022, a four-patient outbreak sustained by occurred in a hospital in Rome. Phenotypic analyses defined these strains as eXtensively Drug-Resistant (XDR). Whole-genome sequencing was performed on the representative strains and resulted in fully closed genomes and plasmids. The genomes were highly related phylogenetically and encoded various virulence factors, including fimbrial clusters. The XDR phenotype was primarily driven by the presence of the metallo-β-lactamase alongside the 16S rRNA methyltransferase, conferring resistance to most β-lactams and every aminoglycoside, respectively. These genes were found on an IncC plasmid that was highly related to an NDM-IncC plasmid retrieved from a ST15 strain circulating in the same hospital two years earlier. Given its ability to acquire resistance plasmids and its intrinsic resistance mechanisms, is a formidable pathogen. The emergence of XDR strains poses a significant public health threat. It is essential to monitor the spread of these strains and develop new strategies for their control and treatment.