Validation of a High-Throughput Screening Assay for Identification of Adjunctive and Directly Acting Antimicrobials Targeting Carbapenem-Resistant Enterobacteriaceae.

ABSTRACT: We describe development and validation of a high-throughput screen (HTS) for identifying small molecules that restore the efficacy of carbapenems (adjunctives) and/or directly inhibit growth of carbapenem-resistant Enterobacteriaceae (CRE). Our HTS assay is based on a screen-counterscreen approach using a representative multidrug-resistant CRE strain, Klebsiella pneumoniae BIDMC12A. Specifically, we tested the ability of small molecules to inhibit bacterial growth in the presence (screen) or absence (counterscreen) of meropenem, a representative carbapenem antibiotic. Primary screening of 11,698 known bioactive compounds identified 14 with adjunctive activity and 79 with direct antimicrobial effect. Secondary screening identified triclosan as a strongly synergistic meropenem adjunctive (fractional inhibitory concentration?=?0.48) and confirmed azidothymidine (AZT) (minimal inhibitory concentration [MIC]?=?4??g mL(-1)), NH125 (MIC?=?4??g mL(-1)), diphenyleneiodonium chloride (MIC?=?8??g mL(-1)), and spectinomycin (MIC?=?32??g mL(-1)) as potent direct antimicrobials. Spectrum of activity of AZT and spectinomycin was tested against a collection of 103 representative Enterobacteriaceae strains (?50% CRE). AZT, a nucleoside analog used to treat human immunodeficiency virus, demonstrated an MIC50 of 2??g mL(-1). Spectinomycin, an antibiotic used to treat gonorrhea, had an MIC50 of 32??g mL(-1). Therefore, a significant percentage of CRE strains appeared relatively susceptible to these antimicrobials. These data identified AZT and spectinomycin as available agents warranting further study for potential treatment of multidrug-resistant CRE infection. Our results provide proof of principle and impetus for performing a large-scale HTS for discovery of novel, small-molecule adjunctives and antibacterial agents directly targeting CRE.

SUBMITTER: Smith KP 

PROVIDER: S-EPMC4841070 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature