Drug susceptibility profiling of Australian Burkholderia species as models for developing melioidosis therapeutics

Background:. Melioidosis is a neglected tropical disease caused by the Gram-negative soil bacterium Burkholderia pseudomallei. Current treatment regimens are prolonged and costly, and acquired antimicrobial resistance has been reported for all currently used antibiotics. Objectives: Efforts to develop new treatments for melioidosis are hampered by the risks associated with handling pathogenic B. pseudomallei, which restricts research to facilities with Biosafety Level (BSL) 3 containment. Closely related Burkholderia species that are less pathogenic can be investigated under less stringent BSL 2 containment. We hypothesized that near-neighbour Burkholderia species could be used as model organisms for developing therapies that would also be effective against B. pseudomallei. Methods: We used microbroth dilution assays to compare the susceptibility of three Australian B. pseudomallei isolates and five near-neighbour Burkholderia species - B. humptydooensis, B. thailandensis, B. oklahomensis, B territorii and B. stagnalis - to antibiotics currently used to treat melioidosis, and general-use antibacterial agents. We also established the susceptibility profiles of B. humptydooensis and B. territorii to 400 compounds from the Medicines for Malaria Venture Pathogen Box. Results: From these comparisons, we observed a high degree of similarity in the susceptibility profiles of B. pseudomallei and near-neighbour species B. humptydooensis, B. thailandensis, B. oklahomensis and B. territorii. Conclusions: Less pathogenic Australian Burkholderia species B. humptydooensis, B. thailandensis, B. oklahomensis and B. territorii are excellent model organisms for developing potential new therapies for melioidosis.