A Metaproteomics Approach to Elucidate Host and Pathogen Protein Expression during Catheter-Associated Urinary Tract Infections (CAUTIs)

Abstract

Long-term catheterization inevitably leads to a catheterassociated bacteriuria caused by multispecies bacterial biofilms growing on and in the catheters. The overall goal of the presented study was (1) to unravel bacterial community structure and function of such a uropathogenic biofilm and (2) to elucidate the interplay between bacterial virulence and the human immune system within the urine. To this end, a metaproteomics approach combined with in vitro proteomics analyses was employed to investigate both, the pro-and eukaryotic protein inventory. Our proteome analyses demonstrated that the biofilm of the investigated catheter is dominated by three bacterial species, that is, Pseudomonas aeruginosa, Morganella morganii, and Bacteroides sp., and identified iron limitation as one of the major challenges in the bladder environment. In vitro proteome analysis of P. aeruginosa and M. morganii isolated from the biofilm revealed that these opportunistic pathogens are able to overcome iron restriction via the production of siderophores and high expression of corresponding receptors. Notably, a comparison of in vivo and in vitro protein profiles of P. aeruginosa and M. morganii also indicated that the bacteria employ different strategies to adapt to the urinary tract. Although P. aeruginosa seems to express secreted and surfaceexposed proteases to escape the human innate immune system and metabolizes amino acids, M. morganii is able to take up sugars and to degrade urea. Most interestingly, a comparison of urine protein profiles of three long-term catheterized patients and three healthy control persons demonstrated the elevated level of proteins associated with neutrophils, macrophages, and the complement system in the patient's urine, which might point to a specific activation of the innate immune system in response to biofilm-associated urinary tract infections. We thus hypothesize that the often asymptomatic nature of catheter-associated urinary tract infections might be based on a fine-tuned balance between the expression of bacterial virulence factors and the human immune system. Molecular & Cellular Proteomics 14: 10.1074/mcp.M114.043463, 989-1008, 2015.Catheter-associated urinary tract infections (CAUTIs) 1 account for up to 40% of all nosocomial infections and are thus the most prevalent source of hospital-acquired infectious diseases (1, 2). CAUTIs are mostly "asymptomatic" and characterized by less than 10 5 colony-forming units per milliliter urine, which do not cause any signs of infection or symptoms. A symptomatic CAUTI, usually correlated to a number of colony-forming units (CFUs) exceeding the above mentioned threshold, is diagnosed when symptoms commonly associated with urinary tract infections (e.g. fever, dysuria, urgency, flank pain, or leukocytosis) occur (3). The risk that CAUTIs become symptomatic increases dramatically during catheterFrom the ‡Institute

Similar Neutrophil-Driven Inflammatory and Antibacterial Responses in Elderly Patients with Symptomatic and Asymptomatic Bacteriuria

“…The myeloid cell nuclear differentiation antigen (MNDA) manipulates neutrophil apoptosis (53). Two previous studies identified neutrophil proteins via proteomics from urethral catheter samples but did not include experiments comparing ASB patients to UTI patients (13,21). We conclude that fundamental defense mechanisms in elderly pa-tients diagnosed with ASB implicate neutrophils as effector cells to kill the invading pathogen.…”

“…Wound repair processes are also initiated (19,20). These immune system activities also pertain to the defense against urethral catheter-associated microbial biofilms (21). Acute inflammation implicates the sensation of pain and development of fever, and prostanoids are among the main pain and fever signaling molecules (22,23).…”

Comprehensive Metaproteomic Analyses of Urine in the Presence and Absence of Neutrophil-Associated Inflammation in the Urinary Tract

“…Enterobacteriaceae species such as Proteus mirabilis and Klebsiella pneumoniae form biofilms in the urinary tract 35 and were each present in two samples with on average 107 and 267 protein IDs, respectively. In sample #29, 222 proteins were identified for Staphylococcus species (137 proteins from S. aureus and 85 proteins from S. saprophyticus ).…”

“…Recently, we introduced metaproteomic approaches for the analysis of UP fractions to identify uropathogens and assess inflammatory responses for the infected patients more comprehensively 33, 34. A similar approach was employed to survey the proteome of poly-bacterial urethral catheter biofilms 35. The association of urinary tract microbial communities with urogenital health has been discussed, enabled by next generation metagenomics sequencing methods 36.…”

Current state of the art for enhancing urine biomarker discovery

“…Several database repositories and urine proteomic resources are now available for locating information regarding urinary protein names, pathophysiology, literature citations, and consensus documents for analytical methods (Table 2). Many of the issues encountered in proteomic profiling and biomarker discovery, including sample preparation and pre-analytical variables [2, 26-31], interfering substances such as bacteria, antibiotics, and x-ray contrast media [32-34], the need for standardized procedures [35-39] and inter-laboratory comparisons [40], have been debated and extensively reviewed elsewhere [36, 41-45]. This review presents a snapshot of the current state of urinary protein biomarker discovery, with emphasis on pre-analytical processing and fractionation methodologies for improving the detection of low abundance proteins and/or protein classes, such as glycoproteins.…”