Objectives: A strategic system for the screening and testing of new antibiotics was created to facilitate the development of antibiotics that are robustly effective against MDR bacteria. Methods: In-frame deletion, site-directed mutagenesis and plasmid transformation were used to generate genetically engineered strains with various resistance mechanisms from a fully susceptible clinical isolate of Klebsiella pneumoniae . Antimicrobial susceptibility testing and a mouse infection model were used to test antibiotics against these strains in vitro and in vivo , respectively. Results: A total of 193 strains, including 29 strains with chromosome-mediated resistance, 33 strains with plasmid-mediated resistance and 131 strains with a combination of both resistance mechanisms were constructed; these strains covered resistance to beta-lactams, quinolones, aminoglycosides, tetracyclines, folate pathway inhibitors and other antibiotics. MICs for all strains were tested, and the effects of genetic modifications on increasing the MICs were assessed. Ceftazidime and cefotaxime were used to assess the correlation between antibacterial activities in vitro and in vivo . Against a K. pneumoniae strain with bla OXA-48 , ceftazidime had a lower MIC (0.5 mg/L) than cefotaxime (2 mg/L). Ceftazidime had an ED 50 of 30 mg/kg, and no mice survived treatment with the same dose of cefotaxime. A positive correlation was observed between these in vitro and in vivo results. Conclusions: The system developed here could reduce the considerable time required to evaluate the effectiveness of new antibiotics against MDR bacteria, particularly in the early stages of drug development. This system could also be expanded as new resistance mechanisms emerge.
Date:
2017-12
Relation:
Journal of Antimicrobial Chemotherapy. 2017 Dec;72(12):3302-3316.
