A model, mixed-species urinary catheter biofilm derived from spinal cord injury patients

Complex multispecies biofilms consistently colonise urinary catheters, causing persistent asymptomatic bacteriuria and frequent symptomatic episodes in long-term catheterized individuals. Simple single-species models often fail to capture the complexities of mixed-species interactions and lab-based organisms may not reflect the genomic diversity found in real-world infections. Additionally, growth under flow conditions promotes robust, complex-biofilm structures. Therefore, to reflect the dynamics of in vivo infections, biofilm samples from clinical indwelling catheters of spinal cord injury (SCI) participants colonised by 5-10 species were used to establish polymicrobial macro-fluidic models, in catheters. This resulted in final models of 2-4 species biofilms. Metagenomic techniques using short-read Illumina and long-read Oxford Nanopore sequencing was used to assess the taxonomic composition, in vivo to in vitro biofilms diversity shifts, single nucleotide polymorphism (SNP) analysis and complete metagenome-assembled genomes (MAGs). In silico analysis revealed a high number of varied antibiotic resistance genes, virulence factors and biofilm associated factors present in these biofilms. Antibiotic resistance testing using our models highlighted the drastic differences between planktonic bacteria, single-species and multispecies biofilms. While single-species biofilms show considerably increased tolerance to antibiotics compared to their planktonic counterparts, this resistance is even greater in multispecies biofilms. Under flow conditions, all species in the multispecies biofilm showed increased resistance, unlike static conditions where only most did. Models developed and characterised in this study are expected to facilitate testing of effective strategies to prevent and treat catheter-associated infections by enabling more accurate analysis of biofilm inhibition, disruption and microbial interactions.