In vitro Activity of Meropenem/Vaborbactam and Imipenem/Relebactam Against Serine Carbapenemase-Producing Klebsiella pneumoniae Isolates in a tertiary care hospital in Ceará, Brazil

Abstract

Objective: tothe present study aimed to evaluate the susceptibility of serine-carbapenemase-producing K. pneumoniae strains to the novel antimicrobial combinations Meropenem/Vaborbactam and Imipenem/Relebactam, developed for the treatment of infections caused by carbapenemase-producing bactéria Methods: antimicrobial susceptibility testing was performed using the gradient strip method for each of these antibiotic combinations. Strains were collected starting in July 2025, yielding a total of 16 samples containing K. pneumoniae isolates identified by the VITEK 2 system as serine-carbapenemase producers, detected through the phenotypic tests mCIM, eCIM, and CARBA-5. A total of 16 Meropenem/Vaborbactam strips and 10 Imipenem/Relebactam strips were tested. The isolates were grouped according to their susceptibility to the antibiotics routinely used in clinical practice and compared with one another. A significance level of p < 0.05 was adopted. Results: the mortality rate among patients in the study was 13%, and the minimum inhibitory concentration (MIC) values observed ranged from 0.032 to 1.000 μg/mL for Meropenem/Vaborbactam and from 0.125 to 0.750 μg/mL for Imipenem/Relebactam, with no considerable variations according to the bacterial resistance profile. Conclusions: these findings demonstrate that the antimicrobial combinations exhibit considerable in vitro activity against the bacterial strains, as the minimum inhibitory concentrations obtained were below the clinical breakpoints established by BrCAST.