Genotypic And Phenotypic Characterisation Of Isolates Of Burkholderia cepacia From Cystic Fibrosis

Clode, Fiona Elizabeth (2003). Genotypic And Phenotypic Characterisation Of Isolates Of Burkholderia cepacia From Cystic Fibrosis. MPhil thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f70a

Abstract

Burkholderia cepacia has become an important cause of lung infections in cystic fibrosis sufferers of whom approximately 20% succumb to severe and often fatal necrotizing pneumonia and septicaemia. The factors which cause this are largely unknown as are those factors predisposing to epidemic spread. At present, published data only confirms that certain strains notably the UK epidemic strain EX 12 can spread amongst the CF population.

Another problem facing scientists which also impinges on patients and their carers, is the difficulty in isolating B. cepacia in mixed specimens and its subsequent identification and differentiation from closely related species which may also colonise the CF lung. Identification has recently been compounded by the identification of more than one species or genomovar of B. cepacia.

This study compared traditional phenotypic methods of identifying B. cepaciawith PGR methods and also evaluated direct detection of the organism in sputum by PGR. The presence of B. cepacia in the natural environment was determined by culturing environmental samples on selective media.

Putative epidemic markers in B. cepacia were detected and this was correlated with genomovar group and RAPD fingerprint.

Finally, the distribution of various virulence markers including serum sensitivity and presence of EPS were monitored and were also correlated with genomovar group.

The results of this study showed that PGR methods for the identification of B. cepacia are more sensitive and specific than traditional methods and allow for its direct detection in sputa. Only the UK epidemic strain appears to spread epidemically in the UK and this strain is most reliably identified by the presence of the cable pili gene (cblA). Serum sensitivity and correlation with strain-type and presence of EPS was significant as was the presence of intracellular enzymes and strain or genomovar group. However the significance of these enzymes in pathogenicity remains uncertain.