Evaluation of the in vitro efficacy of antimicrobials against Enterobacterales with multiple carbapenemase enzymes.

High-dose of carbapenems and combination therapies with new β-lactam/β-lactamase inhibitors and polymyxin B/tigecycline have been considered for treatment of carbapenem resistant Enterobacterales infection. The research was conducted to evaluate the in vitro potency of aminoglycosides, ceftazidime/avibactam/aztreonam and tigecycline against isolates of Enterobacteriaceae with multiple carbapenemase enzymes. 42 genotypically confirmed carbapenem resistant Enterobacterales (twenty-nine NDM producers, nine NDM and OXA-48 producers, three NDM and VIM producers and one NDM combined with VIM and OXA 48 producer) were included. Minimum inhibitory concentration for carbapenems, aminoglycosides and tigecycline was determined by Vitek 2. Ceftazidime/avibactam/aztreonam synergy was observed by disk diffusion methodology. The in vitro efficacy of aminoglycosides was observed against Escherichia coli (E. coli) isolates with NDM and VIM genes. Low tigecycline susceptibility was observed among Klebsiella pneumoniae (K. pneumoniae) isolates with NDM and OXA-48 genes. Ceftazidime -avibactam/aztreonam combination displayed good in vitro activity against dual carbapenemase producers of E. coli isolates (NDM with OXA-48 and NDM with VIM genes) and Klebsiella pneumoniae (combination of NDM, VIM and OXA-48 genes). Ceftazidime/avibactam/aztreonam, aminoglycosides and tigecycline displayed in vitro activity against dual carbapenemase producers of E. coli and K. pneumoniae.