The exploration of phage-based therapeutics for multi-drug resistant bacterial pathogens

• Author / Creator

  Davis, Carly Maddison

• Pathogenic bacteria have a plethora of mechanisms to survive within the human body, and the effectiveness of antibiotics to treat these infections is rapidly declining due to an increase in antimicrobial resistance (AMR) and a lack of new drug discovery. AMR is a significant global concern, and these infections are predicted to cause over 10 million deaths per year worldwide by 2050 if left unchecked. It is clear that alternative antibacterial strategies are desperately needed, and the therapeutic use of bacteriophages is a promising area of research. Phages are viruses that target and lyse bacterial cells via adsorption to cells using a cellular receptor, injecting their genetic material, and replicating themselves until the cell bursts. Phages use a different mechanism than antibiotics to kill bacteria, so many antibiotic resistance mechanisms carried by AMR bacteria provide no protection against phage infection. This means phages are an effective tool to kill drug-resistant bacteria, and unlike antibiotics, phages exclusively attack and lyse specific host bacteria, leaving beneficial bacterial flora unharmed. To explore the efficacy of phage as an alternative treatment option I examined the application of phages in combination with sub-inhibitory (non-lethal) levels of the antibiotic aztreonam lysine (AzLys) on Pseudomonas aeruginosa, a high priority member of the ESKAPE pathogens; a concerning group of pathogenic bacteria exhibiting multi-drug resistance and virulence, are responsible for the majority of nosocomial infections, and are associated with the highest risk of mortality. Activity of phages E79 and phiKZ were increased in the presence of aztreonam lysine, in part due to accelerated time to lysis. Sub-inhibitory AzLys negatively affected the function of surface virulence factors type 4 pili (T4P) and flagella, and the combined treatment of P. aeruginosa biofilms with E79 and non-lethal levels of AzLys was more effective than phage treatment alone. To continue investigating phage therapy, I assembled, annotated, and analyzed the complete iii genomes of two novel phages JC1 and Carl1 that can infect the deadly opportunistic pathogen Burkholderia cenocepacia. I further characterized JC1 and showed it possesses an impressive host range, uses the inner core of the LPS as its cellular surface receptor, and has a high virulence index at 37˚C. I also identified the attP site and location of integration in its bacterial host genome when it takes the form of a prophage. Genetic engineering of this phage could result in a promising phage therapy candidate for the treatment of B. cenocepacia infections. Continued research on the isolation, characterization, and application of phages is necessary so the use of phage as a therapy can become an accessible treatment option for chronic and antibiotic resistant infections.

• Subjects / Keywords

  • phage therapy
  • burkholderia

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-ze79-5a91

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.