Frontiers in Cellular and Infection Microbiology (Dec 2011)
Long-term colonization of the cystic fibrosis lung by Burkholderia cepacia complex bacteria: epidemiology, clonal variation and genome-wide expression alterations
Abstract
Long-term respiratory infections with Burkholderia cepacia complex (Bcc) bacteria in cystic fibrosis (CF) patients generally lead to a more rapid decline in lung function and, in some cases, to a fatal necrotizing pneumonia known as the cepacia syndrome. Bcc bacteria are ubiquitous in the environment and are recognized as serious opportunistic pathogens that are virtually impossible to eradicate from the CF lung, posing a serious clinical threat. The epidemiological survey of Bcc bacteria involved in respiratory infections at the major Portuguese CF Treatment Centre at Santa Maria Hospital, in Lisbon, has been carried out by our research group for the past 16 years, covering over 500 clinical isolates where B. cepacia and B. cenocepacia are the predominant species, with B. stabilis, B. contaminans, B. dolosa and B. multivorans also represented. The systematic and longitudinal study of this CF population during such an extended period of time represents a unique case study, comprehending 41 Bcc-infected patients (29 pediatric and 12 adult) of whom around 70% have been persistently colonized between 7 months and 9 years. During chronic infection, the CF airways represent an evolving ecosystem, with multiple phenotypic variants emerging from the clonal population and becoming established in the patients’ airways as the result of genetic adaptation. Understanding these evolutionary mechanisms is crucial for an improved therapeutic outcome of chronic infections in CF. This review will focus on our contribution to the study of the adaptive mechanisms underlying the clonal variation and expansion that are found to occur during long-term colonization of the CF airways with Bcc. Our analysis is based on extensive phenotypic, genotypic and genome-wide expression approaches of selected Bcc serial isolates obtained during chronic colonization of the mentioned CF subpopulation.
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