Characterisation of burkholderia cepacia from clinical and environmental origins

Abstract

Burkholderia cepacia isolates were obtained from the sputum of cystic fibrosis patients or isolated from the environment. The isolates were characterised phenotypically by determining antibiotic resistance profiles and their ability to macerate onion tissue, and genetically by PCR ribotyping and macro-restriction analysis (genome fingerprinting). The replicon (chromosomal) organisation was determined by pulsed field gel electrophoresis (PFGE) and the presence of plasmids was also investigated. Plasmid transfer by conjugation was also investigated. A high degree of genetic and phenotypic variation was found both within and between clinical and environmental populations of B. cepacia. Environmental isolates were generally less resistant to antibiotics but showed greater ability to macerate onion tissue. Genetic characterisation showed little evidence of acquisition of B. cepacia from the environment by CF patients, but revealed strong evidence supporting person-to- person transmission of B. cepacia in the Cardiff CF centre and other European centres. Two or more chromosomes were found in 93 % of B. cepacia isolates tested, and were also found in other closely related species suggesting such organisation may be common in β-2 proteobacteria. Plasmids, often in excess of 100 kb, were found to be harboured in 52 Yo of isolates, though were more commonly found in CF isolates (65 % of isolates) than environmental isolates (23 % of isolates). Plasmid transfer by conjugation was demonstrated into, between and from B. cepacia strains. Evidence of plasmids encoding antibiotic resistance was also found.