Abstract
Recent metagenomic analyses imply an immense abundance of phages in the human body. Samples collected from different sites (lungs, skin, oral cavity, intestines, ascitic fluid, and urine) reveal a generally greater number of phage particles than that of eukaryotic viruses. The presence of phages in those tissues and fluids reflects the paths they must overcome in the human body, but may also relate to the health statuses of individuals. Besides shaping bacterial metabolism and community structure, the role of phages circulating in body fluids has not been fully understood yet. The lack of relevant reports is especially visible with regard to the human urobiome. Certainly, phage presence and the role they have to fulfill in the human urinary tract raises questions on potential therapeutic connotations. Urinary tract infections (UTIs) are among the most common bacterial infections in humans and their treatment poses a difficult therapeutic dilemma. Despite effective antibiotic therapy, these infections tend to recur. In this review, we summarized the recent data on phage presence in the human urinary tract and its possible implications for health and disease.
Highlights
Our bodies are inhabited by trillions of indigenous microorganisms
Phages could contribute to local defenses within the urinary tract in a number of ways: (a) phages may induce beta-defensins known to have a role on the protection of urinary tract infections (UTIs) [67,68]; (b) most phages assayed do not downregulate Toll-like receptor 4 (TLR4) expression [68], which is relevant in view of the findings suggesting that normal TLR may protect against UTI [67]; (c) neutrophil-derived reactive oxygen species (ROS) may damage the urothelium promoting exfoliation [67], while phages are known to have anti-inflammatory properties downregulating ROS production by neutrophils [69]
The discovery of a virome in the body fluids such as cerebrospinal fluid (CSF) is a clear indication that none of the niches in the human body may be considered sterile
Summary
Our bodies are inhabited by trillions of indigenous microorganisms. In addition to this statement, the idea that all bacteria, fungi, viruses, and other microorganisms impact our health has been growing as well. The fact that over 80% of healthy individuals were found to have Escherichia coli antiphage (anti-T4) antibodies in their sera reflects vast and continuous interplay between phages and cells of the human immune system [13] Human body fluids, such as a serum, urine, and, to a lesser extent, saliva, constitute one of the largest sources of biomarkers. Vast prevalence of phages in different sites of the body could be responsible for horizontal gene transfer between phage and bacterial genomes enhancing survival of bacteria through acquiring new beneficial functions, such as resistance to antibiotics It has already been pointed out by Thannesberger et al [17] on the example of human oropharynx and the urinary tract. In line with the above, the aim of this article is to find an answer to what is the role of urinary microbiome with phages as its significant component
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