Factors influencing the three-dimensional structure of urinary biofilms

Abstract

Catheter-associated urinary tract infection is the most common type of urinary tract infection among healthcare-associated infections that are caused by biofilms developing on the catheter. The study aims to investigate the urinary biofilm characteristics and the genes associated with the biofilm formation on the urinary catheter. Rapid cell attachment occurred as early as 1 h showed that the artificial urine medium supports biofilm growth of uropathogens. AUBK is the most physicochemically similar artificial urine media to urine that promoted better biofilm development on the urinary catheter compared to other laboratory media. Pseudomonas aeruginosa PAO1 is studied as a model organism for urinary biofilm to describe the biofilm development common traits, including the initial attachment, aggregation of cells, and the build-up of microcolonies surrounded by the extracellular polymeric substances. Screening of urease, quorum-sensing, polysaccharide and attachment/motility gene mutants showed that the involvement of the genes differs at different stages of biofilm development. Mutants of rhlB, pelA, pslD, fliC, fliM, pilA biofilm were affected at 1 h during essential initial cell adherence that prevents cells from returning to the planktonic state. Mutants with lasI, rhlI, pqsA, pqsE and fliC produced flat biofilms instead of the characteristic three-dimensional mature biofilm at 24 h, showing that biofilm was unable to differentiate into mature biofilms without cell signalling and flagella-mediated motility. Biofilms of urease and alginate gene-deficient mutants were not affected and had no significant role in urinary biofilm. We also discovered a new, unreported unique feature in the P. aeruginosa PAO1 urinary biofilm formation that mediates cell translocation to the nearest microcolony, observed at 1 h and 3 h timepoints. This study highlights the roles of essential genes in biofilm formation as well as the need to use appropriate artificial urine medium in the urinary biofilm studies as nutrient availability impacts profoundly on urinary biofilm growth and development.

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Identifiers

ORCID for Charles Keevil: orcid.org/0000-0003-1917-7706

ORCID for Sandra Wilks: orcid.org/0000-0002-4134-9415

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