Genomic characterization of carbapenemase-producing Klebsiella pneumoniae ST307 revealed multiple introductions in Buenos Aires, Argentina.

Objectives: To describe at genomic level nine carbapenemase-producing Klebsiella pneumoniae ST307 (Kp-ST307) clinical isolates recovered in Buenos Aires during 2017 to 2021, investigating their resistome, virulome, and phylogeny.
Methods: Antimicrobial susceptibility was determined according to Clinical and Laboratory Standards Intitute (CLSI). Genomic DNA was sequenced by Illumina MiSeq and analysed using SPAdes, PROKKA, and Kleborate. Phylogeny of 355 randomly selected Kp-ST307 genomes and those from nine local isolates was inferred by a maximum-likelihood approach. The tree was visualized using Microreact.
Results: Besides resistance to ß-lactams and fluoroquinolones, six out of nine Kp-ST307 were also resistant to ceftazidime/avibactam (CZA). This difficult-to-treat resvistance phenotype was mediated by bla _SHV-28 and GyrA-83I/ParC-80I mutations in addition to carbapenemase coding genes. Among CZA susceptible isolates, two of them harboured bla _KPC-3 while the other harboured bla _KPC-2 +bla _CTX-M-15. Regarding CZA-resistant isolates, three harboured bla _KPC-3 +bla _NDM-1 +bla _CMY-6 , two carried bla _KPC-2 +bla _NDM-5 +bla _CTX-M-15 , and bla _NDM-5 +bla _CTX-M-15 were detected in the remaining isolate. Furthermore, five colistin-resistant isolates presented a nonsense mutation in mgrB. Global Kp-ST307 isolates were distributed in two deep-branching lineages while local isolates were set in the main clade of the phylogenetic tree. The five isolates from the same hospital, harbouring bla _KPC-3 or bla _KPC-3 +bla _NDM-1 +bla _CMY-6 , clustered in a monophyletic subclade with Italian isolates. Also, an isolate harbouring bla _KPC-2 +bla _NDM-5 +bla _CTX-M-15 recovered in another hospital was closed to this group. The remaining local Kp-ST307 were grouped in other subclades containing isolates of diverse geographical origin.
Conclusion: The inferred resistome was consistent with the resistant phenotype. Phylogeny suggested multiple introduction events in our region and a single major introduction in one hospital followed by local spread.
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