Investigating the molecular mechanisms and role(s) in Infection of biofilm formation by Klebsiella pneumoniae

  • Carly Webb

Student thesis: Doctoral ThesisDoctor of Philosophy


Klebsiella pneumoniae is an urgent health threat which has been identified by world medical agencies as a major risk to public health. The lack of efficient medicines against infectious diseases is becoming one of the leading causes of mortality worldwide. Gram-negative pathogens are becoming increasingly resistant to current medical innovations, whereby if no prompt action is taken will result in no treatments being available. One way that multiple pathogens including K. pneumoniae have evolved to become increasingly resilient to current human medicine is by existing in biofilms. Living within a highly-organised community has become an important survival strategy due to the many advantages that it has versus existing in a planktonic state. Living within a biofilm results in increased drug-resistance of bacteria due to the gradient of both nutrients and oxygen which are linked to an increase in doubling times of bacterial cells and a decrease in metabolism. Biofilms are also linked with an upregulation in efflux pumps, mutations in antibiotic targets (Høiby et al., 2010) . It is therefore important that research is performed to fully understand and begin tackling them. Biofilm formation is important for K. pneumoniae dissemination and virulence. This research aimed to investigate which genes are involved in biofilm formation in K. pneumoniae 52145 using an extensive random mutagenesis approach in optimal screening conditions. These genes were then characterised to identify their role in both the biofilm and within the host. A total of eighty-five hits were found to be involved in biofilm formation in K. pneumoniae. There were hits in multiple previously identified biofilm-related genes involved in fimbriae, sugar transporters, transcriptional regulators, capsule synthesis, metabolism, and O-antigen. However, there were many hits that were in found in this study that have not been previously identified in other K. pneumoniae transposon screens. These included hits in polysaccharides, siderophores, Type VI secretion system and peptidoglycan. Fimbriae and cellulose were also found for the first time to play a role in virulence in G. mellonella. There were several hits in T6SS secretion system related genes which is a novel area regarding biofilm formation and has not been reported in K. pneumoniae previously. Overall, this work is the first time that a transposon screen investigating biofilm formation has been performed in K. pneumoniae 52145, which has revealed that there are a multitude of genes involved in biofilm formation. This study has provided a foundation in which further research can be performed to further characterise the role that these hits play in both biofilm formation and in host pathogen interactions. Due to the increase in antibiotic resistance, it is vital that alternative therapies are investigated. The hits identified in this study could be used towards potential therapeutic targets in the future to tackle K. pneumoniae 52145 living in biofilms in the respiratory tract of patients.
Date of AwardJul 2023
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsDepartment of Education Northern Ireland
SupervisorJose Bengoechea (Supervisor) & Miguel A. Valvano (Supervisor)


  • Klebsiella pneumoniae
  • biofilm formation
  • Transposon Library
  • antibiotic resistance
  • polysaccharide
  • Galleria Mellonella
  • Type VI secretion system
  • gram negative
  • bacterial pathogens
  • mutagenesis

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