Characterization of a Francisella tularensis-caenorhabditis elegans pathosystem for the evaluation of therapeutic compounds

Elamparithi Jayamani, Nagendran Tharmalingam, Rajmohan Rajamuthiah, Jeffrey J. Coleman, Wooseong Kim, Ikechukwu Okoli, Ana M. Hernandez, Kiho Lee, Gerard J. Nau, Frederick M. Ausubel, Eleftherios Mylonakis

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Francisella tularensis is a highly infectious Gram-negative intracellular pathogen that causes tularemia. Because of its potential as a bioterrorism agent, there is a need for new therapeutic agents. We therefore developed a whole-animal Caenorhabditis elegans-F. tularensis pathosystem for high-throughput screening to identify and characterize potential therapeutic compounds. We found that the C. elegans p38 mitogen-activate protein (MAP) kinase cascade is involved in the immune response to F. tularensis, and we developed a robust F. tularensis-mediated C. elegans killing assay with a Z= factor consistently of 0.5, which was then utilized to screen a library of FDA-approved compounds that included 1,760 small molecules. In addition to clinically used antibiotics, five FDA-approved drugs were also identified as potential hits, including the anti-inflammatory drug diflunisal that showed anti-F. tularensis activity in vitro. Moreover, the nonsteroidal anti-inflammatory drug (NSAID) diflunisal, at 4 MIC, blocked the replication of an F. tularensis live vaccine strain (LVS) in primary human macrophages and nonphagocytic cells. Diflunisal was nontoxic to human erythrocytes and HepG2 human liver cells at concentrations of 32 g/ml. Finally, diflunisal exhibited synergetic activity with the antibiotic ciprofloxacin in both a checkerboard assay and a macrophage infection assay. In conclusion, the liquid C. elegans-F. tularensis LVS assay described here allows screening for anti-F. tularensis compounds and suggests that diflunisal could potentially be repurposed for the management of tularemia.

Original languageEnglish
Article numbere00310-17
JournalAntimicrobial Agents and Chemotherapy
Issue number9
StatePublished - Sep 2017

Bibliographical note

Publisher Copyright:
Copyright © 2017 American Society for Microbiology. All Rights Reserved.


  • Antibiotic
  • Caenorhabditis elegans
  • Diflunisal
  • Drug repurposing
  • Francisella
  • High-throughput screen
  • Tularemia


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