JCM Accepts, published online ahead of print on 4 November 2009

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J. Clin. Microbiol. doi:10.1128/JCM.01433-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Oxidative stress of Burkholderia cenocepacia induces insertion sequence mediated genomic rearrangements that interfere with macrorestriction based genotyping

Pavel Drevinek^*, Adam Baldwin, Laurens Lindenburg, Lovleen Tina Joshi, Angela Marchbank, Sarka Vosahlikova, Christopher G. Dowson, and Eshwar Mahenthiralingam

Cardiff School of Biosciences, Cardiff University, Cardiff. UK; Department of Biological Sciences, Warwick University, Coventry. UK; Paediatric Department, 2^nd Medical School, Charles University, Prague, Czech Republic

^* To whom correspondence should be addressed. Email: pavel.drevinek{at}Lfmotol.cuni.cz.

Burkholderia cenocepacia can cause serious infections and epidemics in patients with cystic fibrosis (CF). A CF population in the Czech Republic experienced an epidemic outbreak caused by a B. cenocepacia strain ST-32. Clonality of the isolates was evident by multilocus sequence typing, however fingerprinting profiles obtained by pulsed-field gel electrophoresis (PFGE) showed substantial band variability. We explored if the PFGE pattern diversity had resulted from genomic rearrangements mediated by insertion sequences (IS); in addition we determined if stressful growth altered their transposition activity. DNA probes for IS commonly found in B. cenocepacia were designed using the B. cenocepacia J2315 genome. Southern hybridization analysis of ST-32 isolates demonstrated diversity in both copy number and insertion site for a homologue of ISBcen20. Movement of the ISBcen20 homologue was detected when the ST-32 isolate CZ1238 was exposed to oxidative stress (growth in the presence of H₂O₂). PFGE analysis of these CZ1238 derivatives exposed to oxidative stress demonstrated genomic rearrangements. Interestingly, when the closely related B. cenocepacia J2315 genome strain was exposed to oxidative stress, no movement of ISBcen20 was detected. As frameshift mutation is present within the transposase of all copies of this IS in J2315, our data suggests that the transposase is inactive. In summary, we have demonstrated for the first time that IS movement can be mediated by oxidative stress and lead to genomic rearrangements in the CF pathogen B. cenocepacia. These IS movements may alter the PFGE fingerprints of isolates that are clonal by other typing methods.