KPC-2-Producing Carbapenem-Resistant Klebsiella pneumoniae of the Uncommon ST29 Type Carrying OXA-926, a Novel Narrow-Spectrum OXA β-Lactamase

We isolated and characterized a carbapenem-resistant Klebsiella pneumoniae (CRKP) clinical strain from blood carrying a novel bla(OXA) gene, bla(OXA–926), and belonging to ST29, an uncommon CRKP type. The strain, 130002, was genome sequenced using both short- and long-read sequencing and has a 94.9-kb self-transmissible IncFII plasmid carrying bla(KPC–2). K. pneumoniae genomes of the ST29 complex (ST29 and its single-allele variants) were retrieved and were subjected to single nucleotide polymorphism-based phylogenomic analysis. A total of 157 genomes of the ST29 complex were identified. This complex is commonly associated with extended-spectrum β-lactamase-encoding genes, in particular, bla(CTX–M–15) but rarely has carbapenemase genes. The novel plasmid-encoded β-lactamase-encoding gene bla(OXA–926) was identified on a 117.8-kb IncFIA-IncFII plasmid, which was transferrable in the presence of the bla(KPC–2)-carrying plasmid. bla(OXA–926) was cloned and MICs of β-lactams in the transformants were determined using microdilution. OXA-926 has a narrow spectrum conferring reduced susceptibility only to piperacillin, piperacillin-tazobactam, and cephalothin. Avibactam cannot fully inhibit OXA-926. bla(OXA–926) and its variants have been seen in Klebsiella strains in Asia and Brazil. OXA-926 is the closest in sequence identity (89.9%) to a chromosome-encoding OXA-type enzyme of Variovorax guangxiensis. In conclusion, OXA-926 is novel plasmid-borne narrow-spectrum β-lactamase that cannot be fully inhibited by avibactam. It is likely that bla(OXA–926) originates from a species closely related to V. guangxiensis and was introduced into Klebsiella > 10 years ago.