Efficacy of ceftazidime/avibactam and plazomicin on carbapenem-resistant Klebsiella pneumoniae and Escherichia coli.

Carbapenem-resistant Enterobacterales (CRE) have become a major public health problem worldwide. The aim of this study was to investigate efficacy of ceftazidime/avibactam and plazomicin on carbapenem-resistant Klebsiella pneumoniae and Escherichia coli isolates. Susceptibility of imipenem, meropenem, ertapenem, ceftazidime/avibactam and plazomicin was investigated by broth-microdilution method. Major carbapenemases NDM, VIM, IMP, KPC, OXA-48 as well as other β-lactamases namely, TEM, SHV, OXA-1-like, CTX-M, ACC, FOX, MOX, DHA, CIT, EBC, VEB, GES, PER were investigated by PCR. A total of 120 carbapenem-resistant isolates (60 E. coli and 60 K. pneumoniae) were included in this study and blaOXA-48-like was found in 78.33%, blaNDM in 26.66%, blaKPC in 7.5%, blaIMP in 5.83%, and blaVIM in 5%. Among 94 isolates with the blaOXA-48-like gene, 22.3% were resistant to ceftazidime/avibactam and 51.1% were resistant to plazomicin. Of 32 isolates with blaNDM, 31 (96.9%) were resistant to ceftazidime/avibactam and 30 (93.75%) were resistant to plazomicin, and both antibiotics had limited effects against blaNDM carriers (P < 0.001). Of the 12 isolates with blaNDM+OXA-48 combination, 11 (91.7%) were resistant to ceftazidime/avibactam and plazomicin. The effect of both antibiotics was significantly lower in strains with blaNDM+OXA-48 combination (P < 0.005).The most common carbapenemase genes in this study were blaOXA-48-like and blaNDM. Ceftazidime/avibactam demonstrated a good efficacy among OXA-48 producing K. pneumoniae and E. coli, however, plazomicin had a significantly lower antibacterial effect in our study. Both antimicrobial agents should be considered as an option by evaluating combined susceptibility results and gene patterns obtained by regional and global molecular data in the treatment of CRE infections.