Synergistic antimicrobial combination of third-generation cephalosporins and polymyxin B against carbapenem-polymyxin-resistant Klebsiella pneumoniae: an in vitro and in vivo analysis

Antimicrob Agents Chemother. 2024 Oct 8;68(10):e0093024. doi: 10.1128/aac.00930-24. Epub 2024 Sep 10.

Abstract

Antibiotic combination therapy is a promising approach to address the urgent need for novel treatment options for infections caused by carbapenem-polymyxin-resistant Klebsiella pneumoniae (CPR-Kp). The present study aimed to investigate the synergistic potential of four cephalosporins in combination with polymyxin B (PMB). A checkerboard assay was performed to evaluate the synergistic effects of cephalexin (CLX), cefixime, cefotaxime (CTX), and cefmenoxime (CMX) in combination with PMB. Subsequently, experiments evaluating the use of CTX or CMX in combination with PMB (CTX-PMB or CMX-PMB, respectively), including growth curve and SynergyFinder analysis, antibiofilm activity assays, cell membrane integrity assays, and scanning electron microscopy, were performed. Safety assessments were also conducted, including hemolysis and toxicity evaluations, using Caenorhabditis elegans. Furthermore, an in vivo model in C. elegans was adopted to assess the treatment efficacy against CPR-Kp infections. CTX-PMB and CMX-PMB exhibited low fractional inhibitory concentration indexes ranging from 0.19 to 0.50 and from 0.25 to 1.5, respectively, and zero interaction potency scores of 37.484 and 15.076, respectively. The two combinations significantly reduced growth and biofilm formation in CPR-Kp. Neither CTX-PMB nor CMX-PMB compromised bacterial cell integrity. Safety assessments revealed a low hemolysis percentage and high survival rates in the C. elegans toxicity evaluations. The in vivo model revealed that the CTX-PMB and CMX-PMB treatments improved the survival rates of C. elegans. The synergistic effects of the CTX-PMB and CMX-PMB combinations, both in vitro and in vivo, indicate that these antibiotic pairings could represent effective therapeutic options for infections caused by CPR-Kp.

Keywords: Caenorhabditis elegans; Klebsiella pneumoniae; antimicrobial resistance; cephalosporins; combination therapy.

MeSH terms

  • Animals
  • Anti-Bacterial Agents* / pharmacology
  • Anti-Bacterial Agents* / therapeutic use
  • Biofilms* / drug effects
  • Caenorhabditis elegans* / drug effects
  • Carbapenems / pharmacology
  • Carbapenems / therapeutic use
  • Cephalosporins* / pharmacology
  • Cephalosporins* / therapeutic use
  • Drug Resistance, Multiple, Bacterial / drug effects
  • Drug Synergism*
  • Drug Therapy, Combination
  • Klebsiella Infections / drug therapy
  • Klebsiella Infections / microbiology
  • Klebsiella pneumoniae* / drug effects
  • Microbial Sensitivity Tests*
  • Polymyxin B* / pharmacology
  • Polymyxin B* / therapeutic use

Substances

  • Polymyxin B
  • Anti-Bacterial Agents
  • Cephalosporins
  • Carbapenems