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Published on: November 24, 2017
Burkholderia thailandensis is virulent in Drosophila melanogaster
Martina Pilátová1, Marc S Dionne
1Department of Craniofacial Development, Dental Institute, School of Medicine, King's College London, London, United Kingdom.
Abstract:
Melioidosis is a serious infectious disease endemic to Southeast Asia and Northern Australia. This disease is caused by the Gram-negative bacterium Burkholderia pseudomallei; Burkholderia thailandensis is a closely-related organism known to be avirulent in humans. B. thailandensis has not previously been used to infect Drosophila melanogaster. We examined the effect of B. thailandensis infection on fly survival, on antimicrobial peptide expression, and on phagocytic cells. In the fruit fly, which possesses only an innate immune system, B. thailandensis is highly virulent, causing rapid death when injected or fed. One intriguing aspect of this infection is its temperature dependence: infected flies maintained at 25°C exhibit rapid bacterial proliferation and death in a few days, while infected animals maintained at 18°C exhibit very slow bacterial proliferation and take weeks to die; this effect is due in part to differences in immune activity of the host. Death in this infection is likely due at least in part to a secreted toxin, as injection of flies with sterile B. thailandensis-conditioned medium is able to kill. B. thailandensis infection strongly induces the expression of antimicrobial peptides, but this is insufficient to inhibit bacterial proliferation in infected flies. Finally, the function of fly phagocytes is not affected by B. thailandensis infection. The high virulence of B. thailandensis in the fly suggests the possibility that this organism is a natural pathogen of one or more invertebrates.
Insights
Burkholderia thailandensis is highly virulent in Drosophila melanogaster, causing rapid death. Temperature significantly impacts virulence, with lower temperatures increasing survival, suggesting potential invertebrate pathogenicity.
Area of Science:
- Infectious disease research
- Invertebrate immunology
- Bacteriology
Background:
- Melioidosis, caused by Burkholderia pseudomallei, is a significant infectious disease in tropical regions.
- Burkholderia thailandensis, a related species, is considered non-pathogenic to humans.
- The pathogenicity of B. thailandensis in invertebrates, specifically Drosophila melanogaster, has not been previously investigated.
Purpose of the Study:
- To investigate the virulence of Burkholderia thailandensis in the fruit fly, Drosophila melanogaster.
- To examine the impact of B. thailandensis infection on fly survival, immune responses, and phagocytic activity.
- To explore the temperature-dependent nature of B. thailandensis infection in flies.
Main Methods:
- Infection of Drosophila melanogaster with Burkholderia thailandensis via injection and feeding.
- Monitoring of fly survival rates at different temperatures (18°C and 25°C).
- Analysis of antimicrobial peptide expression and phagocytic cell function in infected flies.
Main Results:
- Burkholderia thailandensis demonstrated high virulence in Drosophila melanogaster, leading to rapid mortality.
- Infection exhibited significant temperature dependence, with flies at 25°C dying faster than those at 18°C.
- Antimicrobial peptide expression was induced but insufficient to control bacterial proliferation; phagocyte function remained unaffected.
Conclusions:
- Burkholderia thailandensis is highly virulent in the fruit fly model, challenging its presumed avirulence.
- Temperature-dependent virulence suggests complex host-pathogen interactions influenced by environmental factors.
- The findings suggest B. thailandensis may be a natural pathogen of certain invertebrates.
