Burkholderia cepacia complex infection in patients with cystic fibrosis

The Burkholderia cepacia complex comprises genetically distinct bacterial species that cause serious infections in cystic fibrosis (CF) patients. Originally classified as a single species, polyphasic taxonomic analysis revealed at least nine genomovars, with six assigned formal species names including B. cepacia, B. multivorans, B. vietnamiensis, B. stabilis, and B. ambifaria. The recA gene provides reliable molecular markers for identifying these genomovars through restriction fragment length polymorphism and DNA sequencing. B. cepacia genomovar III is the predominant CF pathogen, accounting for over 50% of infections across examined populations, followed by B. multivorans at approximately 17% prevalence. Genomovar III strains, particularly those carrying the B. cepacia epidemic strain marker (BCESM), demonstrate significant patient-to-patient transmission capability and are associated with higher mortality and more chronic infections compared to other genomovars. B. multivorans exhibits variable epidemiology, causing severe outbreaks in some populations but remaining non-transmissible in others. The bacteria possess intrinsic antibiotic resistance and large, unusual multi-replicon genomes averaging 8 megabases, contributing to strain-to-strain virulence variation. Genome sequencing projects and detailed epidemiological studies continue to clarify pathogenic mechanisms and inform infection control strategies for CF patients.

Key findings

• The B. cepacia complex comprises at least nine genetically distinct genomovars, with B. cepacia genomovar III and B. multivorans accounting for approximately 95% of CF infections
• B. cepacia genomovar III strains, especially those carrying the BCESM genetic marker, demonstrate epidemic transmissibility between CF patients and are associated with significantly higher mortality and chronic infection compared to other genomovars
• The recA gene provides reliable molecular discrimination of genomovars through RFLP analysis and DNA sequencing, enabling rapid identification directly from patient sputum samples
• B. cepacia complex bacteria possess unusually large multi-replicon genomes (average 8 Mb) with significant strain-to-strain variation, contributing to heterogeneous virulence and pathogenesis among different genomovars and patient populations
• B. multivorans epidemiology and virulence vary geographically, with some CF populations experiencing severe outbreaks and fatal infections while others show minimal transmission, suggesting distinct strain lineage differences