Klebsiella pneumonia biofilm formation and antimicrobial susceptibility during polymicrobial infections of the catheterised urinary tract

: (Alternative Format Thesis)

Abstract

Catheter associated urinary tract infections (CAUTIs) account for around 75% of hospital acquired urinary tract infections (UTIs) and represent a major clinical and economic burden. Urinary catheters are one of the most commonly used medical devices, with their use linked to increased hospital stays, excess mortality and increased antimicrobial resistance. A defining feature of CAUTIs is the formation of biofilm on catheter surfaces. Klebsiella pneumoniae is responsible for around 7.5% of UK CAUTIs and is an opportunistic pathogen with biofilm formation being a factor in its success as a pathogen. Pathogens rarely exist alone in biofilms and this is true of CAUTIs where many infections are polymicrobial. However, there remains a gap in knowledge where studies predominantly focus on monoculture, limiting our appreciation of interspecies biofilm dynamics and the associated impact on treatment outcomes. This study has sought to advance understanding of K. pneumoniae CAUTIs within the context of polymicrobial infections.

To address this, an in vitro model of polymicrobial CAUTI with common uropathogens (Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecalis, Staphylococcus aureus and Proteus mirabilis) has been developed in this study. This model has been utilised to understand how K. pneumoniae behaves within complex polymicrobial community biofilms and how biofilm associated traits influence antimicrobial efficacy. Within polymicrobial biofilms, populations displayed reduced susceptibility to antimicrobial treatment compared with planktonic polymicrobial populations, highlighting the protective effect of polymicrobial biofilms. Presence of different strains of K. pneumoniae was not found to alter community dynamics or structure.

Recognising that clinical exposure of CAUTI uropathogens to biocides can influence bacterial phenotypes, this study examined a chlorhexidine (CHD) adapted derivative of K. pneumoniaeM109, a pre-antibiotic era Murray collection isolate, with mutations in wcaJ, yfiN and smvR. CHD adaptation promoted enhanced biofilm and altered extracellular matrix composition, resulting in dense mucoid biofilms, with the capability to produce mucoid biofilms able to occlude catheter drainage lumens, which is a salient finding. Furthermore, this study13documents K. pneumoniae strains with enhanced biofilm associated with CHD adaptation confers increased biofilm resistance to antimicrobials but increased susceptibility.

Additionally, the high prevalence of K. pneumoniae CAUTI and the high clinical burden combined with the increased antimicrobial resistance burden has underlined the importance of increased fundamental understanding in this bacterium. This study has therefore also utilised transposon disruption of K. pneumoniae capsule biosynthetic machinery to elucidate the relationship between biofilm and capsule presence and their impact on clinically relevant phenotypes.

Overall, this project demonstrates the development of a valuable tool for studying polymicrobial infections of the catheterised urinary tract and documents how this tool has been used to further our understanding of biofilm in K. pneumoniae polymicrobial CAUTIs. Additionally, this project documents the selection of undesirable K. pneumoniae as a result of adaptation to CHD. Together, this study moves the field forward, appreciating the role and impact polymicrobial communities play in CAUTIs and documents salient findings on K.pneumoniae biofilm modulation.

Date of Award	24 Jun 2026
Original language	English
Awarding Institution	University of Bath
Supervisor	Edward Feil (Supervisor), Tiffany Taylor (Supervisor) & Brian Jones (Supervisor)