In vitro activity of newer β-lactam/β-lactamase inhibitor combinations, cefiderocol, plazomicin and comparators against carbapenemase-producing Klebsiella pneumoniae isolates

Infections by carbapenem-resistant Klebsiella pneumoniae (CRKP) remain one of the greatest healthcare threats associated with significant morbidity and mortality. New antimicrobials were recently developed to address this threat. We assessed the epidemiology of carbapenemase-producing K. pneumoniae (CPKP) isolates recovered in a Greek university hospital during 2021, and their susceptibilities to old and newer antimicrobials. Minimum inhibitory concentrations (MICs) were determined by the MIC Test Strip method, except for cefiderocol (CFDC) and colistin that were evaluated by the broth microdilution method. A total of 110 CPKP strains were isolated, with KPC-producers being the most prevalent (64.6%). Among the agents tested, plazomicin (PL) displayed the highest activity against all the isolates (MIC₅₀/MIC₉₀, 0.5/1.5 μg/ml), followed by tigecycline (MIC₅₀/MIC₉₀, 1.5/4 μg/ml). All KPC-producing K. pneumoniae were susceptible to ceftazidime-avibactam (CAZ/AVI) and meropenem-vaborbactam (M/V) and 97.2% of them to imipenem-relebactam (I/R). Among the MBL-producing isolates, PL and CFDC exhibited the highest activity.