Unveiling the genetic architecture and transmission dynamics of a novel multidrug-resistant plasmid harboring bla in E. Coli ST167: implications for antibiotic resistance management.

Background: The emergence of multidrug-resistant (MDR) Escherichia coli strains poses significant challenges in clinical settings, particularly when these strains harbor New Delhi metallo-ß-lactamase (NDM) gene, which confer resistance to carbapenems, a critical class of last-resort antibiotics. This study investigates the genetic characteristics and implications of a novel bla-carrying plasmid pNDM-5-0083 isolated from an E. coli strain GZ04-0083 from clinical specimen in Zhongshan, China.

Results: Phenotypic and genotypic evaluations confirmed that the E. coli ST167 strain GZ04-0083 is a multidrug-resistant organism, showing resistance to diverse classes of antibiotics including ß-lactams, carbapenems, fluoroquinolones, aminoglycosides, and sulfonamides, while maintaining susceptibility to monobactams. Investigations involving S1 pulsed-field gel electrophoresis, Southern blot analysis, and conjugation experiments, alongside genomic sequencing, confirmed the presence of the bla gene within a 146-kb IncFIB plasmid pNDM-5-0083. This evidence underscores a significant risk for the horizontal transfer of resistance genes among bacterial populations. Detailed annotations of genetic elements-such as resistance genes, transposons, and insertion sequences-and comparative BLAST analyses with other bla-carrying plasmids, revealed a unique architectural configuration in the pNDM-5-0083. The MDR region of this plasmid shares a conserved gene arrangement (repA-IS15DIV-bla-ble-IS91-suI2-aadA2-dfrA12) with three previously reported plasmids, indicating a potential for dynamic genetic recombination and evolution within the MDR region. Additionally, the integration of virulence factors, including the iro and sit gene clusters and enolase, into its genetic architecture poses further therapeutic challenges by enhancing the strain's pathogenicity through improved host tissue colonization, immune evasion, and increased infection severity.

Conclusions: The detailed identification and characterization of pNDM-5-0083 enhance our understanding of the mechanisms facilitating the spread of carbapenem resistance. This study illuminates the intricate interplay among various genetic elements within the novel bla-carrying plasmid, which are crucial for the stability and mobility of resistance genes across bacterial populations. These insights highlight the urgent need for ongoing surveillance and the development of effective strategies to curb the proliferation of antibiotic resistance.