Characterization of multidrug resistance in clinical Klebsiella pneumoniae strains carrying drug efflux pumps and multiple repetitive tandem blaKPC-2 core structures.

OBJECTIVE

To elucidate the mechanisms of multidrug resistance in clinical Klebsiella pneumoniae strains that harbor drug efflux pumps and contain multiple tandem repeats of the blaKPC-2 core structure.

METHODS

The characteristics of strains SC7, SC35, SC38, SC41, SC42, SC67, and SC173 were comprehensively examined. This analysis encompassed antimicrobial susceptibility testing, conjugative transfer experiments, and the detection of beta-lactamase and carbapenemase production. The genomes of these strains were sequenced using both Illumina and Nanopore platforms to generate high-quality genomic data. Subsequently, bioinformatics tools were employed to analyze the mobile genetic elements that carry antibiotic resistance genes.

RESULTS

The analyzed K. pneumoniae strains were found to produce class A carbapenemase and exhibited resistance to nearly all tested antibiotics. This resistance was primarily attributed to the presence of efflux pump genes, such as acrAB-tolC, located on the chromosomes. Additionally, these strains contained one or more repetitive tandem core structures of blaKPC-2, as well as blaKPC-2 and/or blaCTX-M-65 core structures within their genomes. Some plasmids also harbored blaSHV-12, blaTEM-1, and rmtB. These genetic structures showed similarities to mobile genetic elements like Tn3 and TnAs3. The identification of strain SC67, which possessed seven tandem repeats of the blaKPC-2 core structure, represents a novel finding and significantly advances our understanding of antibiotic resistance mechanisms. Plasmid transfer assays demonstrated successful conjugation in all strains, with varying average conjugation frequencies. Comparative analyses of the full-length plasmids and the multidrug resistance regions carrying blaKPC-2 and/or blaCTX-M-65 revealed a high degree of evolutionary conservation in these core structures.

CONCLUSIONS

The evolution of these strains is intricately linked to the core structures of blaKPC-2 and/or blaCTX-M-65. Moreover, the presence of multiple drug efflux pumps on the chromosomes significantly contributes to their resistance to nearly all commonly used antibiotics. Given these findings, it is imperative to develop and implement effective strategies to curb the dissemination and prevalence of these highly resistant strains.