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Molecular mechanisms of persistence in Burkholderia cenocepacia biofilms

(2014)
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Abstract
Burkholderia cenocepacia J2315 is a member of the Burkholderia cepacia complex (Bcc), a group of 18 closely related metabolically versatile microorganisms. These opportunistic pathogens can cause severe lung infections in cystic fibrosis patients. Infections are often difficult to treat due to innate resistance of Bcc species to antimicrobials and because of their capacity to form biofilms. One of the mechanisms thought to be involved in biofilm resilience is the presence of persister cells. The main aim of this dissertation was to investigate whether persister cells are present in B. cenocepacia biofilms, what the molecular basis of antimicrobial tolerance is, and how persisters can be eradicated. We confirmed the presence of persister cells in B. cenocepacia biofilms and found that genes encoding proteins involved in ROS production are downregulated in persister cells, whereas the glyoxylate shunt is upregulated. Additionally, we found that toxin antitoxin (TA)-modules are involved in persistence. Searching for TA-modules we also identified an interesting operon (BCAM0257-8) located in the B. cepacia epidemic strain marker region. This module plays a role in persistence and in addition, BCAM0258 functions as a regulator influencing quorum sensing and activating cellular pathways involved in iron acquisition and biofilm formation. Overexpression of BCAM0257 was found to increase virulence in Galleria mellonella. Genes similar to BCAM0257-8 are found in all sequenced B. cenocepacia ET-12 genomes and its presence may help explaining why infections with strains of the B. cenocepacia ET-12 lineage are so difficult to treat. Furthermore, we evaluated in vitro the bacteriostatic and bactericidal activity of temocillin, a 6-α-methoxy-penicillin against planktonic and sessile Bcc bacteria. Our data indicate that, although temocillin has a good bacteriostatic activity against planktonic cultures and 4-h old biofilms, it is of limited use to eradicate mature biofilms.
Keywords
persistence, Burkholderia, ROS, toxin antitoxin modules, biofilm

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Citation

Please use this url to cite or link to this publication:

Chicago
Van Acker, Heleen. 2014. “Molecular Mechanisms of Persistence in Burkholderia Cenocepacia Biofilms”. Ghent, Belgium: Ghent University. Faculty of Pharmaceutical Sciences.
APA
Van Acker, Heleen. (2014). Molecular mechanisms of persistence in Burkholderia cenocepacia biofilms. Ghent University. Faculty of Pharmaceutical Sciences, Ghent, Belgium.
Vancouver
1.
Van Acker H. Molecular mechanisms of persistence in Burkholderia cenocepacia biofilms. [Ghent, Belgium]: Ghent University. Faculty of Pharmaceutical Sciences; 2014.
MLA
Van Acker, Heleen. “Molecular Mechanisms of Persistence in Burkholderia Cenocepacia Biofilms.” 2014 : n. pag. Print.
@phdthesis{4412032,
  abstract     = {Burkholderia cenocepacia J2315 is a member of the Burkholderia cepacia complex (Bcc), a group of 18 closely related metabolically versatile microorganisms. These opportunistic pathogens can cause severe lung infections in cystic fibrosis patients. Infections are often difficult to treat due to innate resistance of Bcc species to antimicrobials and because of their capacity to form biofilms. One of the mechanisms thought to be involved in biofilm resilience is the presence of persister cells. 
The main aim of this dissertation was to investigate whether persister cells are present in B. cenocepacia biofilms, what the molecular basis of antimicrobial tolerance is, and how persisters can be eradicated.
We confirmed the presence of persister cells in B. cenocepacia biofilms and found that genes encoding proteins involved in ROS production are downregulated in persister cells, whereas the glyoxylate shunt is upregulated.  Additionally, we found that toxin antitoxin (TA)-modules are involved in persistence. Searching for TA-modules we also identified an interesting operon (BCAM0257-8) located in the B. cepacia epidemic strain marker region. This module plays a role in persistence and in addition, BCAM0258 functions as a regulator influencing quorum sensing and activating cellular pathways involved in iron acquisition and biofilm formation. Overexpression of BCAM0257 was found to increase virulence in Galleria mellonella. Genes similar to BCAM0257-8 are found in all sequenced B. cenocepacia ET-12 genomes and its presence may help explaining why infections with strains of the B. cenocepacia ET-12 lineage are so difficult to treat. 
Furthermore, we evaluated in vitro the bacteriostatic and bactericidal activity of temocillin, a 6-\ensuremath{\alpha}-methoxy-penicillin against planktonic and sessile Bcc bacteria. Our data indicate that, although temocillin has a good bacteriostatic activity against planktonic cultures and 4-h old biofilms, it is of limited use to eradicate mature biofilms.},
  author       = {Van Acker, Heleen},
  language     = {eng},
  pages        = {211},
  publisher    = {Ghent University. Faculty of Pharmaceutical Sciences},
  school       = {Ghent University},
  title        = {Molecular mechanisms of persistence in Burkholderia cenocepacia biofilms},
  year         = {2014},
}