Biocontrol of Burkholderia cepacia complex bacteria and bacterial phytopathogens by Bdellovibrio bacteriovorus.

Bdellovibrio and like organisms are predatory bacteria that have the unusual property of using the cytoplasmic constituents of other Gram-negative bacteria as nutrients. These predators may thus provide an alternative approach to the biocontrol of human and plant pathogens. Predators were isolated on Burkholderia cenocepacia K56-2 and J2315 as prey cells, in enrichment cultures with soil and sewage. Three isolates (DM7C, DM8A, and DM11A) were identified as Bdellovibrio bacteriovorus on the basis of morphology, a periplasmic life cycle, and 16S rRNA gene sequencing. The prey range of these isolates was tested on Burkholderia cepacia complex bacteria and several phytopathogenic bacteria of agricultural importance. Of 31 strains of the Burkholderia cepacia complex tested, only 4 were resistant to predation by strain DM7C. A subset of 9 of the prey tested were also susceptible to strains DM8A and DM11A. Of 12 phytopathogens tested, 4 were resistant to strains DM7C and DM8A, and only 2 were resistant to strain DM11A. Thus, Bdellovibrio bacteriovorus strains retrieved from environmental samples on 2 Burkholderia cenocepacia isolates from cystic fibrosis patients did not distinguish in their prey range between other isolates of that pathogen or phytopathogens. Such strains hold promise as potential wide-spectrum biocontrol agents.

Isolation of Burkholderia cenocepacia and Burkholderia vietnamiensis from human sewage.

Fresh human sewage was examined from a sewage treatment plant for the presence of members of the Burkholderia cepacia complex (BCC) of bacterial organisms and confirmed the presence of viable B. cenocepacia and B. vietnamiensis, by a combination of cultural, phenotypic and genotypic techniques. Both these organisms are important respiratory pathogens for patients with cystic fibrosis (CF). Presently, the survival dynamics of these organisms in sewage effluent and sludge is, as yet, unknown. Therefore, as this study represents the first report of these CF pathogens in sewage and until such survival data is available, careful risk assessment needs to be undertaken in relation to the end use application of potentially contaminated sewage and where such material comes into association with non-colonised patients with cystic fibrosis, so that any potential transmission of these pathogens from sewage to patient is assessed and minimised/eliminated.

Design and performance of a 16S rRNA-targeted oligonucleotide probe for detection of members of the genus Bdellovibrio by fluorescence in situ hybridization.

A 16S rRNA-targeted, Cy3-labeled oligonucleotide probe was designed to detect members of the genus Bdellovibrio by fluorescence in situ hybridization. Specific hybridization conditions were established; however, the detection of bdellovibrios in environmental samples required enrichment, confirming that Bdellovibrio spp. are not present in large numbers in the environment.