Related Experiment Video
Updated: Nov 1, 2025
Development of a Polymicrobial Colony Biofilm Model to Test Antimicrobials in Cystic Fibrosis
Published on: September 20, 2024
Transcriptomics Analysis Uncovers Transient Ceftazidime Tolerance in Burkholderia Biofilms
Supaksorn Chattagul1,2, Mohd M Khan3,4, Alison J Scott5
1Department of Biochemistry, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
Abstract:
Burkholderia pseudomallei is an etiological agent of melioidosis, a severe community-acquired infectious disease. B. pseudomallei strain K96243 is sensitive to the drug ceftazidime (CAZ), but has been shown to exhibit transient CAZ tolerance when in a biofilm form. To investigate an observed shift in gene expression profile during CAZ tolerance condition and to better understand the mechanistic aspects of this transient tolerance, RNA-sequencing was performed on B. pseudomallei K96243 from the following three states: planktonic, biofilm, and planktonic shedding. Results indicated that the expression of 651 genes (10.97%) were significantly changed in both biofilm (resistant) and planktonic shedding (sensitive) cells in comparison to the planktonic state. The top four highly expressed genes identified in both states are associated with nitrosative stress response (BPSL2368), Fe-S homeostasis (BPSL2369), and nitrate respiration (BPSS1154 and BPSS1158). Additionally, five orthologous genes, BPSL2370-BPSL2374, implicated in Fe-S cluster biogenesis, and another gene, BPSL2863, involved in DNA-binding of the stress protein ferritin, were shown to increase expression by RT-qPCR. The shift in gene expression was especially prominent at the late stages of biofilm growth (72 and 96 h), specifically in the biofilm-challenged CAZ survivor cells. This suggested that in response to stress in a biofilm, differential expression of these genes may support development of the CAZ tolerance in Burkholderia. The application of iron chelator deferoxamine (DFO) to the biofilm caused a significant reduction in biofilm formation and associated CAZ tolerance. Therefore, the shift in Fe-S metabolism when B. pseudomallei is in a biofilm may help stabilize the levels of reactive oxygen species (ROS), thereby limiting tolerance to CAZ.
Insights
Burkholderia pseudomallei biofilms develop tolerance to ceftazidime (CAZ) by altering gene expression, particularly related to iron-sulfur metabolism and stress responses. Targeting iron metabolism with deferoxamine (DFO) reduced this CAZ tolerance.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- *Burkholderia pseudomallei* causes melioidosis, a severe infectious disease.
- This bacterium exhibits transient ceftazidime (CAZ) tolerance in biofilms, complicating treatment.
- Understanding the mechanisms behind this tolerance is crucial for developing effective therapies.
Purpose of the Study:
- To investigate gene expression changes in *B. pseudomallei* during ceftazidime tolerance in biofilms.
- To elucidate the mechanistic basis of transient CAZ tolerance in *B. pseudomallei* biofilms.
- To explore potential therapeutic targets for overcoming CAZ tolerance.
Main Methods:
- RNA-sequencing was performed on *B. pseudomallei* K96243 in planktonic, biofilm, and planktonic shedding states.
- Gene expression profiles were compared across different growth conditions and in response to CAZ.
- RT-qPCR was used to validate the expression of specific genes.
- The effect of iron chelator deferoxamine (DFO) on biofilm formation and CAZ tolerance was assessed.
Main Results:
- Significant changes in the expression of 651 genes (10.97%) were observed in biofilm and planktonic shedding states compared to the planktonic state.
- Highly expressed genes were associated with nitrosative stress response, Fe-S homeostasis, and nitrate respiration.
- Expression of genes involved in Fe-S cluster biogenesis and DNA-binding of ferritin increased, particularly in late-stage biofilms.
- Deferoxamine (DFO) treatment significantly reduced biofilm formation and associated CAZ tolerance.
Conclusions:
- A shift in Fe-S metabolism and stress response gene expression contributes to ceftazidime tolerance in *B. pseudomallei* biofilms.
- Stabilization of reactive oxygen species (ROS) via altered Fe-S metabolism may limit CAZ tolerance.
- Targeting iron metabolism presents a potential strategy to overcome CAZ tolerance in melioidosis treatment.
