title: Complete killing of Caenorhabditis elegans by Burkholderia pseudomallei is dependent on prolonged direct association with the viable pathogen.
abstract: BACKGROUND
  Burkholderia pseudomallei is the causative agent of melioidosis, a disease of significant morbidity and mortality in both human and animals in endemic areas. Much remains to be known about the contributions of genotypic variations within the bacteria and the host, and environmental factors that lead to the manifestation of the clinical symptoms of melioidosis.
  
  
  RESULTS
  In this study, we showed that different isolates of B. pseudomallei have divergent ability to kill the soil nematode Caenorhabditis elegans. The rate of nematode killing was also dependent on growth media: B. pseudomallei grown on peptone-glucose media killed C. elegans more rapidly than bacteria grown on the nematode growth media. Filter and bacteria cell-free culture filtrate assays demonstrated that the extent of killing observed is significantly less than that observed in the direct killing assay. Additionally, we showed that B. pseudomallei does not persistently accumulate within the C. elegans gut as brief exposure to B. pseudomallei is not sufficient for C. elegans infection.
  
  
  CONCLUSIONS
  A combination of genetic and environmental factors affects virulence. In addition, we have also demonstrated that a Burkholderia-specific mechanism mediating the pathogenic effect in C. elegans requires proliferating B. pseudomallei to continuously produce toxins to mediate complete killing.
authors.affiliation: School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia.
authors.forename: Song-Hua
authors.initials: SH
authors.lastname: Lee
authors.forename: Soon-Keat
authors.initials: SK
authors.lastname: Ooi
authors.forename: Nor Muhammad
authors.initials: NM
authors.lastname: Mahadi
authors.forename: Man-Wah
authors.initials: MW
authors.lastname: Tan
authors.forename: Sheila
authors.initials: S
authors.lastname: Nathan
mesh_terms: D000818:Animals; D016957:Burkholderia pseudomallei / Q000302:isolation & purification / Q000472:pathogenicity*; D017173:Caenorhabditis elegans / Q000382:microbiology*; D004058:Diffusion; D004198:Disease Susceptibility; D004777:Environment; D041981:Gastrointestinal Tract / Q000382:microbiology / Q000473:pathology; D054884:Host-Pathogen Interactions; D006801:Humans; D051379:Mice; D014118:Toxins, Biological / Q000378:metabolism
chemical_list: D014118:Toxins, Biological