Mechanisms of resistance to ceftazidime/avibactam in mutants derived in vitro from Klebsiella pneumoniae producing OXA-48-like enzymes

  • J Antimicrob Chemother. 2025 Sep 29:dkaf360. doi: 10.1093/jac/dkaf360.
T Blanco-Martín  1  2  3 ,  J Guzmán-Puche  1  2  3 ,  M Hernández-García  3  4 ,  M Muñoz-Rosa  1  2 ,  C Elías-López  2  3 ,  C Riazzo  1  2 ,  J Torre-Cisneros  2  3  5  6 ,  J Arca-Suárez  3  7 ,  M Causse  1  2  3 ,  G Bou  3  7  8 ,  R Cantón  3  4 ,  L Martínez-Martínez  1  2  3  9
Affiliations
  • 1. Unidad de Gestión Clínica de Microbiología, Hospital Universitario Reina Sofía, Córdoba, Spain.
  • 2. Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.
  • 3. CIBER de Enfermedades Infecciosas (CIBERINFEC), Instituto de Salud Carlos III, Madrid, Spain.
  • 4. Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain.
  • 5. Servicio de Enfermedades Infecciosas, Hospital Universitario Reina Sofía, Córdoba, Spain.
  • 6. Departamento de Ciencias Médicas y Quirúrgicas, Universidad de Córdoba, Córdoba, Spain.
  • 7. Servicio de Microbiología and Instituto de Investigación Biomédica A Coruña (INIBIC), Complexo Hospitalario Universitario A Coruña (CHUAC), A Coruña, Spain.
  • 8. Departamento de Fisioterapia, Medicina y Ciencias Biomédicas, Universidad de A Coruña, A Coruña, Spain.
  • 9. Departamento de Química Agrícola, Edafología y Microbiología, Universidad de Córdoba, Córdoba, Spain.
PMID: 41016856 DOI: 10.1093/jac/dkaf360
Abstract

Objectives: To generate in vitro ceftazidime-avibactam-resistant mutants derived from Klebsiella pneumoniae producing OXA-48 or OXA-48 derivatives OXA-131 and OXA-232 carbapenemases, to define their antimicrobial susceptibility phenotype and to analyse mutations potentially involved in resistance to ceftazidime-avibactam.

Methods: Mutants were obtained by plating overnight Bacterial cultures on Mueller-Hinton agar plates containing increasing concentrations of ceftazidime-avibactam (0.5/4-32/4 mg/L). MICs were determined using Sensititre™ DKMNG panels. Whole-genome Sequencing of 8 parental strains and 31 mutant derivatives was performed with Illumina.

Results: All parental strains were susceptible to ceftazidime-avibactam (MIC ≤ 0.5/4-2/4 mg/L) and either susceptible or resistant to meropenem (MIC 0.5 to >16 mg/L) and imipenem (MIC ≤ 0.5 to >16 mg/L). MICs of ceftazidime-avibactam for the mutants increased up to 4 to >16 mg/L, while MICs of meropenem and imipenem for most mutants either increased up to >16 mg/L or remained unchanged. Whole-genome Sequencing of the mutants identified alterations in genes coding for proteins related to AcrAB-TolC (AcrB, AcrR), PBPs (PBP2, PBP3), porins (OmpK36, EnvZ) or the stress or stringent responses (RseB, CpxA, SpoT). No mutations were detected in genes coding for OXA-48-like Enzymes or Other β-lactamases.

Conclusions: Ceftazidime-avibactam can select in vitro mutants of OXA-48-like carbapenemase-producing K. pneumoniae resistant to this combination and, in some cases, also to carbapenems. No mutations related to ceftazidime-avibactam resistance were found in genes coding OXA-48-like Enzymes, but they were detected in genes related to active efflux, PBPs, permeability or proteins of the stress and stringent responses.

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