Characterization of phylogroups of Klebsiella pneumoniae (K. quasipneumoniae and K. variicola) harbouring bla OXA-232, with special reference to ceftazidime/avibactam/aztreonam synergy and their genetic profile

  • JAC Antimicrob Resist. 2026 Jul 4;8(4):dlag104. doi: 10.1093/jacamr/dlag104.
Tuhina Banerjee  1 ,  Kajal Mishra  1 ,  Pue Rakshit  1 ,  Ghanshyam Yadav  2 ,  Ashok Kumar  3
Affiliations
  • 1. Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
  • 2. Department of Anaesthesiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India.
  • 3. Department of Paediatrics, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.
PMID: 42405347 DOI: 10.1093/jacamr/dlag104
Abstract

Background: Klebsiella pneumoniae is a 'critical priority' pathogen responsible for several infections. The emerging evidence of carbapenem resistance in the phylogroups of K. pneumoniae (KpI), namely K. quasipneumoniae (KpII) and K. variicola (KpIII), has drawn attention.

Objectives: Given the paucity of data, this study was conducted to characterize phylogroups harbouring bla OXA-232 with special reference to ceftazidime/avibactam/aztreonam (CAZ/AVI/ATM) synergy.

Methods: This cross-sectional study was performed on 150 previously characterized K. pneumoniae isolates (KpI, KpII, KpIII). Susceptibility against meropenem, ceftazidime/avibactam, aztreonam, polymyxin B, colistin and cefiderocol was determined using broth microdilution. CAZ/AVI/ATM synergy was assessed using gradient diffusion and disc diffusion methods and confirmed by time-kill assay. Detection of bla OXA-232 and class A, B and D carbapenemase genes was performed by PCR. Clonality of the ceftazidime/avibactam-resistant isolates was studied by ERIC-PCR. Susceptibility was compared with the genetic profile by chi-squared and Fisher's exact tests.

Results: Seventy-two isolates (48%) carried bla OXA-232 of which 87.5% were carbapenem resistant; susceptibility to cefiderocol, colistin and polymyxin B was 80.95% (51), 82.5% (52) and 84.12% (53), respectively. Difference in cefiderocol resistance (P = 0.03) and colistin susceptibility (P = 0.03) was significant among phylogroups. CAZ/AVI/ATM synergy was observed in 92.3% (24) of the ceftazidime/avibactam-resistant isolates, with bla OXA-232 alone in 12 (50%), and bla OXA-232 in combination with bla NDM ± bla OXA-48 or other MBLs in 12 (50%). Multiple clones were detected.

Conclusions: Synergy to the CAZ/AVI/ATM combination in the bla OXA-232-positive, ceftazidime/avibactam-resistant, carbapenem-resistant K. pneumoniae phylogroups was noted (92.3%). Cefiderocol and polymyxins were other therapeutic options.

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