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Updated: Aug 30, 2026
An In Vitro Bladder Model of Catheter-Associated Urinary Tract Infection
Published on: June 24, 2025
Molecular epidemiology of Proteus mirabilis infections of the catheterized urinary tract
N A Sabbuba1, E Mahenthiralingam, D J Stickler
1Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom. Sabbuba@cardiff.ac.uk
Abstract:
Proteus mirabilis compromises the care of many patients undergoing long-term indwelling bladder catheterization. It forms crystalline bacterial biofilms in catheters which block the flow of urine, causing either incontinence due to leakage or painful distention of the bladder due to urinary retention. If it is not dealt with, catheter blockage can lead to pyelonephritis and septicemia. We have examined the epidemiology of catheter-associated P. mirabilis infections by use of pulsed-field gel electrophoresis (PFGE) of NotI restriction enzyme digests of bacterial DNA. This technique was shown to be more discriminatory than the classical phenotypic Dienes typing technique. We demonstrated that each of 42 isolates from diverse environmental sources and 10 of 12 isolates from blood, wound swabs, and mid-stream urine samples of hospitalized patients had distinct genotypes. Examination of a set of 55 isolates of P. mirabilis, each from a different clinical or environmental source, identified 49 distinct genotypes and 43 Dienes types. The index of discrimination was 0.993 for the PFGE method and 0.988 for the Dienes method. Applying the PFGE method to isolates from catheter-associated urinary tract infections confirmed that the strains present in the crystalline catheter biofilms were identical to those isolated from the same patient's urine. An analysis of samples taken during a prospective study of infections in catheterized nursing home patients revealed that a single genotype of P. mirabilis can persist in the urinary tract despite many changes of catheter, periods of noncatheterization, and antibiotic therapy.
Insights
Proteus mirabilis causes catheter blockages, leading to serious infections. Pulsed-field gel electrophoresis (PFGE) effectively identified distinct bacterial strains, revealing persistent infections in patients despite treatment.
Area of Science:
- Microbiology
- Infectious Diseases
- Medical Diagnostics
Background:
- Proteus mirabilis is a common cause of catheter-associated urinary tract infections (CAUTIs).
- Bacterial biofilms formed by P. mirabilis in urinary catheters lead to blockage, incontinence, and potentially severe systemic infections like pyelonephritis and septicemia.
- Effective epidemiological tools are needed to understand the transmission and persistence of P. mirabilis strains in clinical settings.
Purpose of the Study:
- To evaluate the discriminatory power of pulsed-field gel electrophoresis (PFGE) for typing catheter-associated Proteus mirabilis isolates.
- To compare the effectiveness of PFGE with the traditional Dienes typing method.
- To investigate the genetic relatedness of P. mirabilis strains from various sources, including environmental, clinical, and catheter biofilms.
Main Methods:
- Pulsed-field gel electrophoresis (PFGE) was used to analyze NotI restriction enzyme digests of bacterial DNA from P. mirabilis isolates.
- Classical phenotypic Dienes typing was performed for comparison.
- Isolates were obtained from diverse environmental sources, clinical samples (blood, wound swabs, urine), and catheter biofilms.
Main Results:
- PFGE demonstrated higher discriminatory power (0.993) compared to Dienes typing (0.988).
- PFGE identified distinct genotypes for most environmental and clinical isolates, indicating diverse origins.
- Analysis of catheter-associated infections confirmed that strains in biofilms were identical to those isolated from the same patient's urine, and a single genotype could persist long-term.
Conclusions:
- PFGE is a highly discriminatory molecular typing method for studying the epidemiology of Proteus mirabilis.
- P. mirabilis strains causing CAUTIs are often persistent within the urinary tract, surviving interventions like catheter changes and antibiotic therapy.
- Understanding strain persistence is crucial for developing strategies to manage and prevent CAUTI.
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