Abstract
Bacteria of the Burkholderia cepacia complex (Bcc) are associated with significant decline of lung functions in cystic fibrosis patients. Bcc infections are virtually impossible to eradicate due to their irresponsiveness to antibiotics. The 2-thiocyanatopyridine derivative 11026103 is a novel, synthetic compound active against Burkholderia cenocepacia. To characterize mechanisms of resistance to 11026103, B. cenocepacia was subjected to chemical mutagenesis, followed by whole genome sequencing. Parallel mutations in resistant isolates were localized in a regulatory protein of the efflux system Resistance-Nodulation-Division (RND)-9 (BCAM1948), RNA polymerase sigma factor (BCAL2462) and its cognate putative anti-sigma factor (BCAL2461). Transcriptomic analysis identified positive regulation of a major facilitator superfamily (MFS) efflux system BCAL1510-1512 by BCAL2462. Artificial overexpression of both efflux systems increased resistance to the compound. The effect of 11026103 on B. cenocepacia was analyzed by RNA-Seq and a competitive fitness assay utilizing an essential gene knockdown mutant library. 11026103 exerted a pleiotropic effect on transcription including profound downregulation of cluster of orthologous groups (COG) category “Translation, ribosomal structure, and biogenesis”. The competitive fitness assay identified many genes which modulated susceptibility to 11026103. In summary, 11026103 exerts a pleiotropic cellular response in B. cenocepacia which can be prevented by efflux system-mediated export.
Highlights
Burkholderia cepacia complex species (Bcc) comprises bacteria from diverse environmental and clinical sources [1]
Bcc thriving in thick cystic fibrosis (CF) sputum are associated with chronic inflammation and significant decline in lung functions; infections with the most virulent Bcc lineages result in death due to a necrotizing septic pneumonia [2,3]
Previous work [8] showed that resistance to 11026103 in spontaneously arising mutants of B. cenocepacia J2315 was exclusively due to overexpression of the efflux system
Summary
Burkholderia cepacia complex species (Bcc) comprises bacteria from diverse environmental and clinical sources [1]. They typically infect hospitalized patients with underlying medical conditions. Patients with cystic fibrosis (CF) are among the ones at the greatest risk of contracting a Bcc infection. Bcc thriving in thick CF sputum are associated with chronic inflammation and significant decline in lung functions; infections with the most virulent Bcc lineages result in death due to a necrotizing septic pneumonia (cepacia syndrome) [2,3]. Poor prognosis of Bcc infections in CF patients is largely a consequence of the irresponsiveness of the microbes to antibiotic treatment. Bcc are intrinsically resistant to several antibiotic classes [4]
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