Urinary Antimicrobial Peptides and the Urinary Microbiota in a UTI-Susceptible Population of Female Pelvic Floor Surgery Patients

Urinary tract infections (UTI)s are a national priority. Women who undergo surgery for pelvic floor disorders such as pelvic organ prolapse (POP) or urinary incontinence (UI) are at increased risk for UTI, as 10-30% will contract a post-instrumentation UTI (postI-UTI) within six weeks after surgery. Currently, the factors that contribute to the high rate of postI-UTI are unknown, and there is currently no clinical assessment to identify at-risk patients. However, antimicrobial peptides (AMPs) and characteristics of the urinary microbiota have the potential to serve as biomarkers, identifying patients at UTI risk and facilitating clinical prevention studies. While it was previously thought that the urinary tract was a sterile environment, new evidence shows that bacteria inhabit the urinary tract in many people. Given that microbial communities (microbiota) in other areas of the body exist in a balance with the host defense system, a similar equilibrium likely exists between the microbiota and host defenses in the urinary tract. AMPs, one significant component of our innate defense system, can limit pathogenic infection by their abilities to interact with and disrupt microbial membranes, and to stimulate immune cell recruitment. While it is reported that certain AMPs are expressed in the urinary tract, the AMP profile of the urinary tract has not been characterized. Inappropriate expression of AMPs in other tissues, including altered levels and/or activity, has been associated with several different disease states. It is therefore possible that POP/UI surgery patients that express inappropriate AMP levels or decreased AMP potency have an imbalance between their defenses and their resident microbiota, which results in their susceptibility to postI-UTI. These results begin to reveal the urinary antimicrobial peptide and microbiota profiles of three cohorts of patients: (1) POP/UI patients with culture-negative urine samples at baseline who DO NOT develop a postI-UTI (2) POP/UI patients with culture-negative urine at baseline who DO develop a postI-UTI, and (3) POP/UI patients with positive clinical cultures at baseline. While levels of two AMPs, psoriasin and human β-defensin-1, do not significantly differ between the cohorts, preliminary evidence suggests that a characteristic microbiota may exist in patients who develop infection. Furthermore, AMPs and the microbiota may directly influence one another. Levels of psoriasin are lower in patients with detectable E. coli in their urine than in patients with other types of infections. In addition to this correlation, the presence of certain genera of bacteria positively correlates with levels of psoriasin. This could indicate that some members of the microbiota, by affecting levels of AMPs, influence the susceptibility of the urinary tract to invading pathogens. By furthering our understanding of urinary AMPs and the urinary microbiota, we take an important step toward being able to identify POP/UI patients who are at high risk for postI-UTI, and toward developing new therapeutic options for preventing infection

Cutaneous Burn Injury Modulates Urinary Antimicrobial Peptide Responses and the Urinary Microbiome

OBJECTIVES: Characterization of urinary bacterial microbiome and antimicrobial peptides after burn injury to identify potential mechanisms leading to urinary tract infections and associated morbidities in burn patients. DESIGN: Retrospective cohort study using human urine from control and burn subjects. SETTING: University research laboratory. PATIENTS: Burn patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Urine samples from catheterized burn patients were collected hourly for up to 40 hours. Control urine was collected from "healthy" volunteers. The urinary bacterial microbiome and antimicrobial peptide levels and activity were compared with patient outcomes. We observed a significant increase in urinary microbial diversity in burn patients versus controls, which positively correlated with a larger percent burn and with the development of urinary tract infection and sepsis postadmission, regardless of age or gender. Urinary psoriasin and β-defensin antimicrobial peptide levels were significantly reduced in burn patients at 1 and 40 hours postadmission. We observed a shift in antimicrobial peptide hydrophobicity and activity between control and burn patients when urinary fractions were tested against Escherichia coli and Enterococcus faecalis urinary tract infection isolates. Furthermore, the antimicrobial peptide activity in burn patients was more effective against E. coli than E. faecalis. Urinary tract infection-positive burn patients with altered urinary antimicrobial peptide activity developed either an E. faecalis or Pseudomonas aeruginosa urinary tract infection, suggesting a role for urinary antimicrobial peptides in susceptibility to select uropathogens. CONCLUSIONS: Our data reveal potential links for urinary tract infection development and several morbidities in burn patients through alterations in the urinary microbiome and antimicrobial peptides. Overall, this study supports the concept that early assessment of urinary antimicrobial peptide responses and the bacterial microbiome may be used to predict susceptibility to urinary tract infections and sepsis in burn patients

Cutaneous Burn Injury Modulates Urinary Antimicrobial Peptide Responses and the Urinary Microbiome

OBJECTIVES: Characterization of urinary bacterial microbiome and antimicrobial peptides after burn injury to identify potential mechanisms leading to urinary tract infections and associated morbidities in burn patients. DESIGN: Retrospective cohort study using human urine from control and burn subjects. SETTING: University research laboratory. PATIENTS: Burn patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Urine samples from catheterized burn patients were collected hourly for up to 40 hours. Control urine was collected from "healthy" volunteers. The urinary bacterial microbiome and antimicrobial peptide levels and activity were compared with patient outcomes. We observed a significant increase in urinary microbial diversity in burn patients versus controls, which positively correlated with a larger percent burn and with the development of urinary tract infection and sepsis postadmission, regardless of age or gender. Urinary psoriasin and β-defensin antimicrobial peptide levels were significantly reduced in burn patients at 1 and 40 hours postadmission. We observed a shift in antimicrobial peptide hydrophobicity and activity between control and burn patients when urinary fractions were tested against Escherichia coli and Enterococcus faecalis urinary tract infection isolates. Furthermore, the antimicrobial peptide activity in burn patients was more effective against E. coli than E. faecalis. Urinary tract infection-positive burn patients with altered urinary antimicrobial peptide activity developed either an E. faecalis or Pseudomonas aeruginosa urinary tract infection, suggesting a role for urinary antimicrobial peptides in susceptibility to select uropathogens. CONCLUSIONS: Our data reveal potential links for urinary tract infection development and several morbidities in burn patients through alterations in the urinary microbiome and antimicrobial peptides. Overall, this study supports the concept that early assessment of urinary antimicrobial peptide responses and the bacterial microbiome may be used to predict susceptibility to urinary tract infections and sepsis in burn patients

Interplay between bladder microbiota and urinary antimicrobial peptides: mechanisms for human urinary tract infection risk and symptom severity.

Resident bacterial communities (microbiota) and host antimicrobial peptides (AMPs) are both essential components of normal host innate immune responses that limit infection and pathogen induced inflammation. However, their interdependence has not been investigated in the context of urinary tract infection (UTI) susceptibility. Here, we explored the interrelationship between the urinary microbiota and host AMP responses as mechanisms for UTI risk. Using prospectively collected day of surgery (DOS) urine specimens from female pelvic floor surgery participants, we report that the relative abundance and/or frequency of specific urinary microbiota distinguished between participants who did or did not develop a post-operative UTI. Furthermore, UTI risk significantly correlated with both specific urinary microbiota and β-defensin AMP levels. Finally, urinary AMP hydrophobicity and protease activity were greater in participants who developed UTI, and correlated positively with both UTI risk and pelvic floor symptoms. These data demonstrate an interdependency between the urinary microbiota, AMP responses and symptoms, and identify a potential mechanism for UTI risk. Assessment of bacterial microbiota and host innate immune AMP responses in parallel may identify increased risk of UTI in certain populations

Bacterial abundance and phylogenetic similarity distinguishes the three UTI cohorts.

<p>Heatmap representing urine specimens clustered according to their phylogenetic similarities. The abundance of each bacterial Order is represented by the blue boxes, with greater abundance indicated by darker blue squares. Y-axis: Dendogram based on phylogenetic similarities. X-axis: Order. POS (Blue), PostI-UTI (Red) and NEG (Green).</p

Comparison of Pelvic Floor Characteristics Based on Culture Status.

<p>Clinical factors were collected and analyzed between the 3 cohorts by chi-squared analysis or one-way ANOVA, as appropriate. Significance within the type of surgery (POP, UI or POP/UI), pre-operative pelvic floor symptom scores (based on pre-operative questionnaire) or post-operative urinary symptom status is indicated as <b><i>p-</i></b><b>value</b> (α = 0.05).</p><p>Comparison of Pelvic Floor Characteristics Based on Culture Status.</p

Bacterial diversity correlates with the susceptibility or resistance to UTI.

<p>Phylogenetic tree comparing the bacterial diversity at the Order level within the female urinary microbiome. The bacterial diversity was compared between the three cohorts: POS (Blue), PostI-UTI (Red) and NEG (Green).</p

Wilcox analysis between Genus and Cohort.

<p>For each of the three analyses, all statistically significant correlations are indicated as <b><i>p</i></b><b> value</b>. Non-significant relationships are left blank. The cohort containing a greater abundance of each genus is indicated as <b>Enriched Cohort</b>. None of the <i>Lactobacillus</i> relationships were significant.</p><p>Wilcox analysis between Genus and Cohort.</p