An in situ high-throughput screen identifies inhibitors of intracellular Burkholderia pseudomallei with therapeutic efficacy

Philip L. Bulterys, Isabelle J. Toesca, Michael H. Norris, Jeffrey P. Maloy, Sorel T. Fitz-Gibbon, Bryan France, Babak Toffig, Marco Morselli, Nawarat Somprasong, Matteo Pellegrini, Herbert P. Schweizer, Apichai Tuanyok, Robert Damoiseaux, Christopher T. French, Jeff F. Miller

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Burkholderia pseudomallei (Bp) and Burkholderia mallei (Bm) are Tier-1 Select Agents that cause melioidosis and glanders, respectively. These are highly lethal human infections with limited therapeutic options. Intercellular spread is a hallmark of Burkholderia pathogenesis, and its prominent ties to virulence make it an attractive therapeutic target. We developed a high-throughput cellbased phenotypic assay and screened ∼220,000 small molecules for their ability to disrupt intercellular spread by Burkholderia thailandensis, a closely related BSL-2 surrogate. We identified 268 hits, and cross-species validation found 32 hits that also disrupt intercellular spread by Bp and/or Bm. Among these were a fluoroquinolone analog, which we named burkfloxacin (BFX), which potently inhibits growth of intracellular Burkholderia, and flucytosine (5-FC), an FDA-approved antifungal drug. We found that 5-FC blocks the intracellular life cycle at the point of type VI secretion system 5 (T6SS-5)-mediated cell-cell spread. Bacterial conversion of 5-FC to 5-fluorouracil and subsequently to fluorouridine monophosphate is required for potent and selective activity against intracellular Burkholderia. In a murine model of fulminant respiratory melioidosis, treatment with BFX or 5-FC was significantly more effective than ceftazidime, the current antibiotic of choice, for improving survival and decreasing bacterial counts in major organs. Our results demonstrate the utility of cell-based phenotypic screening for Select Agent drug discovery and warrant the advancement of BFX and 5-FC as candidate therapeutics for melioidosis in humans.

Original languageEnglish (US)
Pages (from-to)18597-18606
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number37
StatePublished - Sep 10 2019
Externally publishedYes


  • Burkholderia pseudomallei
  • Drug discovery
  • Melioidosis
  • Small molecule
  • Type 6 secretion system (T6SS)

ASJC Scopus subject areas

  • General


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