Fitness cost of ceftazidime-avibactam resistance acquisition in carbapenem-resistant hypervirulent Klebsiella pneumoniae

BMC Microbiol. 2026 Jan 10;26(1):104. doi: 10.1186/s12866-025-04654-5.

Abstract

Background: Antibiotic-resistant Klebsiella pneumoniae (KP) poses a serious global public health threat. However, research on the resistance mechanisms and accompanying phenotypic changes in carbapenem-resistant hypervirulent KP (CR-hvKP) under antibiotic treatment remains limited. This study aims to investigate the resistance mechanisms of CR-hvKP to ceftazidime-avibactam (CAZ-AVI) and its concomitant phenotypic shifts, employing an in vitro induction assay.

Methods: Six ceftazidime-avibactam (CAZ-AVI)-susceptible CR-hvKP clinical isolates were subjected to in-vitro resistance induction. We used pulsed-field gel electrophoresis, whole-genome sequencing, biofilm formation, a Galleria mellonella infection model, and in-vitro competitive growth assays to characterize the virulence and adaptive changes of the isolates.

Results: CAZ-AVI-resistant CR-hvKP demonstrated enhanced biofilm formation capacity, but the G. mellonella infection model indicated a decrease in virulence of the drug-resistant strain. While resistant strains exhibited diminished competitive fitness in vitro, growth curves did not differ significantly. Genomic characterization identified both resistant and susceptible isolates as ST11, with resistant isolates exhibiting an expanded resistance gene profile, primarily involving KPC-2 variants. All strains carried typical virulence determinants, including iroE (a glycosidase gene within the salmochelin siderophore system), iucABCD (the aerobactin biosynthesis operon), and iutA (the gene encoding the outer membrane receptor for ferric-aerobactin).

Conclusions: CAZ-AVI resistance acquisition in CR-hvKP primarily occurs through KPC-2 mutations. Strains harboring such mutations exhibit enhanced biofilm formation capacity but attenuated virulence and competitiveness. Research into these adaptive changes will facilitate the development of improved clinical strategies for the treatment and control of carbapenem-resistant hypervirulent Klebsiella pneumoniae.

Keywords: Carbapenem-resistant hypervirulent Klebsiella pneumoniae; Drug resistance; Fitness cost.

MeSH terms

  • Animals
  • Anti-Bacterial Agents* / pharmacology
  • Azabicyclo Compounds* / pharmacology
  • Bacterial Proteins / genetics
  • Biofilms / drug effects
  • Biofilms / growth & development
  • Carbapenem-Resistant Enterobacteriaceae* / drug effects
  • Carbapenem-Resistant Enterobacteriaceae* / genetics
  • Carbapenem-Resistant Enterobacteriaceae* / pathogenicity
  • Carbapenems* / pharmacology
  • Ceftazidime* / pharmacology
  • Drug Combinations
  • Drug Resistance, Multiple, Bacterial* / genetics
  • Genome, Bacterial
  • Humans
  • Klebsiella Infections / microbiology
  • Klebsiella pneumoniae* / drug effects
  • Klebsiella pneumoniae* / genetics
  • Klebsiella pneumoniae* / pathogenicity
  • Microbial Sensitivity Tests
  • Moths / microbiology
  • Virulence / genetics
  • Whole Genome Sequencing

Substances

  • Ceftazidime
  • Azabicyclo Compounds
  • avibactam, ceftazidime drug combination
  • Drug Combinations
  • Anti-Bacterial Agents
  • Carbapenems
  • Bacterial Proteins