Mass Spectrometry Study of Urinary Protein Deposition on Catheters and Their Effect on Bacterial Growth and Biofilm Formation



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Catheter‑associated urinary tract infections (CAUTIs) are the most common health care‑associated infection. Diverse urinary proteins deposited on the catheter surface will promote biofilm formation and encrustation. In this work, we aim to understand the process of protein deposition from human urine (HU) onto catheter surfaces, the composition of the deposited proteins, their conformational changes, and the intermolecular interactions between these host proteins and bacterial extracellular proteins. Firstly, the silicone catheters were incubated with pooled HU for different time points. For the first time, we identified 1463 human urinary protein groups deposited on silicone urinary catheters after incubation in pooled filter-sterilized healthy HU for 1440 min. This is by far the largest number of urinary proteins reported on catheters. Finally, the time course of human urinary proteins deposited on the catheters are classified into 9 categories. Unfolding and conformational alterations during urinary proteins adsorbed on the catheter surface were confirmed and rationalized using limited proteolysis coupled with LC-MS/MS. The increased average distance between cleavage sites to the least squares (LS) plane indicated that proteins had more conformational/orientational change during interaction with the catheter surface. The potential roles of urinary protein deposition on catheters in uropathogenic colonization were examined. We found that the urinary proteins deposited on catheters promoted the colonization of an asymptomatic strain, E. coli 83972 wild type, and three uropathogens, E. coli CFT073, M. morganii, and E. faecalis OG1RF. We performed proteomic analysis of the extracellular polymeric substances secreted by E. coli 83972 wild type during the early stage of biofilm formation (0.5 h to 4 h) in HU on coated and uncoated catheter surfaces. Label-free relative quantitation revealed 1478 and 1184 EPS proteins in the biofilm on coated and uncoated catheters, respectively. The expression of various virulence factors was up-regulated in coated catheters, which indicated that the deposited human urinary protein promoted bacteria colonization and secretion of virulence factors. These results have important implications for understanding the mechanism of CAUTIs. Finally, we reported a lysine-specific modification and MS-based workflow for probing the accessibility of the deposited proteins.



Catheter-associated Urinary Tract Infection, Urinary Protein, Urinary Catheter, Biofilm Formation