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Antimicrob Agents Chemother. 2016 May 23;60(6):3276-82. doi: 10.1128/AAC.03089-15. Print 2016 Jun.

Inhibitors of Ribosome Rescue Arrest Growth of Francisella tularensis at All Stages of Intracellular Replication.

Author information

1
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA.
2
Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, USA.
3
Department of Microbiology and Immunology, New York Medical College, Valhalla, New York, USA.
4
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA gsk125@psu.edu kkeiler@psu.edu.
5
Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, USA gsk125@psu.edu kkeiler@psu.edu.

Abstract

Bacteria require at least one pathway to rescue ribosomes stalled at the ends of mRNAs. The primary pathway for ribosome rescue is trans-translation, which is conserved in >99% of sequenced bacterial genomes. Some species also have backup systems, such as ArfA or ArfB, which can rescue ribosomes in the absence of sufficient trans-translation activity. Small-molecule inhibitors of ribosome rescue have broad-spectrum antimicrobial activity against bacteria grown in liquid culture. These compounds were tested against the tier 1 select agent Francisella tularensis to determine if they can limit bacterial proliferation during infection of eukaryotic cells. The inhibitors KKL-10 and KKL-40 exhibited exceptional antimicrobial activity against both attenuated and fully virulent strains of F. tularensis in vitro and during ex vivo infection. Addition of KKL-10 or KKL-40 to macrophages or liver cells at any time after infection by F. tularensis prevented further bacterial proliferation. When macrophages were stimulated with the proinflammatory cytokine gamma interferon before being infected by F. tularensis, addition of KKL-10 or KKL-40 reduced intracellular bacteria by >99%, indicating that the combination of cytokine-induced stress and a nonfunctional ribosome rescue pathway is fatal to F. tularensis Neither KKL-10 nor KKL-40 was cytotoxic to eukaryotic cells in culture. These results demonstrate that ribosome rescue is required for F. tularensis growth at all stages of its infection cycle and suggest that KKL-10 and KKL-40 are good lead compounds for antibiotic development.

PMID:
26953190
PMCID:
PMC4879415
DOI:
10.1128/AAC.03089-15
[Indexed for MEDLINE]
Free PMC Article

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