Strategies to combat urinary pathogens in catheter-associated infections

  • May Tayyem

Student thesis: Doctoral ThesisDoctor of Philosophy


Catheter-associated urinary tract infections (CAUTls) are among the most common nosocomial infections. Colonization with urease producing species such as Proteus mirabilis increases urine pH, precipitating struvite crystals, resulting in catheter encrustation . Several approaches have been developed to prevent CAUTls including the modification of catheter surfaces to offset the formation of crystalline biofilmsor modulating urinary pH.

Weak organic acids (WOAs) have been employed as preservatives in food manufacturing for centuries as antimicrobial and antifungal agents.
Inorganic polyphosphate are universally biomolecule polymers, widely used in meat production as preservatives because of their antibacterial activity against Gram-positive, Gram-negative bacteria and yeast. 

The aim of this research is to investigate the capability of using WOAs and polyphosphates as preventative and treatment novel agents against CAUTls and related complications such as catheter blockage and encrustation.
The antimicrobial activities of WOAs against common uropathogens (were investigated through the determination of MIC and MSC values at normal and infected urine pH levels. Time-kill assays were conducted to evaluate the antimicrobial properties of pyruvic and citric acids against P. mirabilis in in vivo relevant conditions.

The antibacterial activities of polyphosphates were explored against urinary pathogens and their ability of polyphosphates to chelate metal ions present in urine and prevent their precipitation as a result of P. mirabilis urease activity was examined through static crystallisation assay and in in vitro bladder models, that determined of their effect on the time to catheter blockage.

The polymicrobial nature of CAUTls was assessed through the study of interspecies interactions between uropathogens in static models and dynamic bladder models. The effect of polymicrobial interactions were also examined on urinary catheter blockage, with regard to WOAs effect against catheter encrustations .Promising antimicrobial activities of WOAs and polyphosphates were observed, with enhanced anti-encrustation characteristics when examined in in vitro bladder models.

 Thesis is embargoed until 31 December 2027.
Date of AwardDec 2022
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsQueen's University Belfast
SupervisorColin McCoy (Supervisor) & Louise Carson (Supervisor)


  • urinary
  • catheter
  • catheter associated infections
  • weak acids
  • polyphosphates
  • proteus mirabilis
  • struvite crystals
  • catheter blockage
  • encrustation

Cite this