Detection of NDM-1 and OXA-10 Co-Producing Providencia rettgeri Clinical Isolate

The coexistence of bla_NDM-1 with other resistance determinants is rarely reported for Providencia rettgeri. Therefore, this study investigates the phenotypic and genetic characteristics of a multidrug-resistant P. rettgeri strain YQ150713.

P. rettgeri YQ150713 was identified as carrying bla_NDM-1. S1-pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, and conjugation experiments were used to determine plasmid characteristics. An antimicrobial susceptibility test was conducted. The complete genomic sequence of YQ150713 was obtained using Illumina NovaSeq 6000 and Oxford nanopore platforms. To further characterize the phylogenetic structure of P. rettgeri YQ150713, average nucleotide identity (ANI) and phylogenetic analyses were conducted.

The S1-PFGE, Southern blot, and conjugation assays have confirmed that the isolate P. rettgeri YQ150713 contains the bla_NDM-1 gene on a conjugative plasmid pYQ150713-NDM-1. Antimicrobial susceptibility testing has indicated that strain YQ150713 was resistant to various common antibiotics, except aztreonam and fosfomycin. Bioinformatics analysis has further shown that pYQ150713-NDM-1 was a novel plasmid with a size of 265,883 bp, and bla_NDM-1 and bla_OXA-10 were co-located on it. Phylogenetic analysis suggesting P. rettgeri has spread widely throughout the world.

In this study, bla_NDM-1 and bla_OXA-10 were co-localized on a novel plasmid pYQ150713-NDM-1 with a horizontal transfer function. To reduce the risk of the dissemination of such P. rettgeri isolates in clinical settings, more surveillance will be required in the future.