Characterization of Klebsiella pneumoniae Carbapenemase (KPC)-14, a KPC Variant Conferring Resistance to Ceftazidime-Avibactam in the Extensively Drug-resistant ST463 Pseudomonas aeruginosa Clinical Isolate.

Objectives: We studied two Klebsiella pneumoniae carbapenemase (KPC)-14 variants from clinical Pseudomonas aeruginosa isolates (C137 and C159) to better understand the genomic diversity, mechanisms, and genes that confer antibiotic resistance and pathogenicity.

Methods: Genomic DNA from C137/159 was subjected to Illumina and Oxford Nanopore sequencing. Horizontal transmission of the plasmid was evaluated using cloning experiments. The expression of efflux pumps, the outer membrane protein OprD, and the enzyme AmpC was quantified using qRT-PCR. The detectability of KPC-14 was evaluated using different methods, and biofilm formation assays and growth curves were assessed.

Results: C137 and C159, sequence type 463 ExoU-positive multidrug-resistant strains, were concurrently resistant to carbapenems and ceftazidime-avibactam (CZA). Both strains possessed five intrinsic antimicrobial resistance genes (fosA, catB7, crpP, bla, and a bla variant) as well as bla. In strain C137, bla was located on a plasmid (pC137). Both strains expressed the bla gene, concurrent inactivation of OprD, overexpression of the MexX efflux pump, and a pronounced capacity for biofilm formation. The genomic environment of KPC-14 consisted of IS26/IS26/TnpR_Tn3/ISKpn27/ISKpn6/IS26, which classified it as pseudo-compound transposon (PCT). IS26-mediated PCTs may store a variety of resistance genes, including bla and KPC variants, which are currently disseminating in this region.

Conclusion: The KPC-14 variant presents significant challenges for clinical treatment. The bla gene carried by PCTs was integrated into the chromosome and exhibited stability throughout bacterial inheritance. Our research highlights the need for improved clinical surveillance of KPC-producing P. aeruginosa.