Burkholderia cepacia complex infection in cystic fibrosis patients mechanisms of pathogenesis

• Published in: Reviews in medical microbiology Vol. 15; no. 3; pp. 93 - 101
• Main Author: Ryley, H C
• Format: Journal Article
• Language: English
• Published: 01-07-2004
• Subjects: Burkholderia cepacia
• ISSN: 0954-139X
• DOI: 10.1097/00013542-200407000-00002

Related species that make up the Burkholderia cepacia complex can be opportunistic pathogens of the lungs of patients with cystic fibrosis (CF). B. multivorans and B. cenocepacia are the predominant clinical isolates from this group. The pathogenesis of B. cepacia complex of the CF lung has certain characteristics. Firstly some strains are found in many patients (hyper-transmissible strains) whereas others are limited to infection of single patients. Attempts to identify specific virulence genes or markers linked to hyper-transmissibility have to date been largely unsuccessful with the possible exception of the expression of a functional 'cable' pilus by one strain. This strain (ET12 lineage) is highly infectious and has widespread distribution. Once acquired it may be suppressed, it is rarely, if ever, eradicated from the CF lung. Virulence factors associated with persistence have been identified and include biofilm formation, the ability of invasion and replication within epithelial tissue, production of siderophores and particular ornibactins and possibly exotoxins directed against phagocytic cells. In addition, recent work using signature tagged mutagenesis and an animal model in which the lungs are infected with agarose embedded B. cenocepacia, has identified more than 100 genes required for in vivo persistence. A third characteristic of B. cepacia complex infection is the variable sequelae following infection from apparent long-term asymptomatic carriage to the development of acute and usually fatal pneumonitis ('B. cepacia syndrome'). The later condition may be associated in part with undefined host responses to the infection together with invasiveness of the complex and the elevated inflammatory cytokine production in response to B. cepacia complex lipopolysaccharide. Although much information concerning the virulence factors of the B. cepacia complex has emerged in the last few years, there are still many aspects that need clarification before our knowledge in this area will have a clinical benefit to patients with CF.