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Swarming of Proteus mirabilis over ureteral stents: a comparative assessment
James D Watterson1, Peter A Cadieux, David Stickler
1Division of Urology, University of Western Ontario, London, Ontario, Canada.
Background And Purpose:
Encrustation on indwelling ureteral stents is commonly related to the presence of urease-producing bacteria that elevate the pH of the urine through the hydrolysis of urea, resulting in the precipitation of calcium and magnesium salts. Using a model previously shown to measure accurately the ability of Proteus mirabilis to swarm over catheter surfaces (Eur J Clin Microbiol Infect Dis 1999;18:206), we investigated the ability of this organism to swarm over three ureteral stents with potential encrustation-resistance properties.
Materials And Methods:
Three commercially available ureteral stents were selected for evaluation: a low surface-energy stent, a hydrogel-coated stent, and a silicone stent. Ten-microliter aliquots of a 4-hour culture of P. mirabilis 296 in Trypticase soya (TSA) broth was inoculated 5 mm from a 1-cm channel cut out from TSA plates. Ten-millimeter stent sections were placed as bridges across the central channel adjacent to the inocula. Time to pathogen crossing was measured.
Results:
The mean time (+/- SD) to pathogen migration across the three test materials was 15.9 +/- 6.1, 19.8 +/- 9.5, and 29.7 +/- 14.3 hours for the low surface-energy, hydrogel-coated, and silicone stents, respectively. Statistical analysis revealed significant differences between the crossing times of the low surface-energy (P = 0.001) and hydrogel-coated (P = 0.034) stents compared with silicone but not between the low surface-energy and hydrogel-coated stents (P = 0.387).
Conclusion:
Migration of P. mirabilis 296 across silicone stents was significantly reduced compared with low surface-energy and hydrogel-coated stents. These findings suggest that P. mirabilis may have a lower affinity for silicone stents, which may translate into a reduced risk of infection with P. mirabilis and associated stent encrustation.
Insights
Silicone ureteral stents showed reduced Proteus mirabilis migration compared to low surface-energy and hydrogel-coated stents. This suggests silicone may lower infection and encrustation risk for indwelling ureteral stents.
Area of Science:
- Urology
- Microbiology
- Biomaterials Science
Background:
- Ureteral stent encrustation is often caused by urease-producing bacteria, like Proteus mirabilis.
- These bacteria increase urine pH, leading to calcium and magnesium salt precipitation.
- A model was used to assess bacterial swarming on different stent materials.
Purpose of the Study:
- To evaluate the encrustation resistance of three ureteral stent types against Proteus mirabilis.
- To compare the ability of P. mirabilis to swarm over low surface-energy, hydrogel-coated, and silicone stents.
Main Methods:
- Three commercial ureteral stents (low surface-energy, hydrogel-coated, silicone) were tested.
- Proteus mirabilis 296 was inoculated on agar plates near stent sections.
- The time for P. mirabilis to migrate across the stent material was measured.
Main Results:
- Silicone stents demonstrated significantly longer pathogen crossing times (29.7 +/- 14.3 hours) compared to low surface-energy (15.9 +/- 6.1 hours) and hydrogel-coated stents (19.8 +/- 9.5 hours).
- Statistical analysis confirmed significant differences between silicone and the other two stent types.
- No significant difference was found between low surface-energy and hydrogel-coated stents.
Conclusions:
- Silicone ureteral stents significantly reduced P. mirabilis migration.
- P. mirabilis appears to have a lower affinity for silicone surfaces.
- These findings suggest silicone stents may reduce the risk of P. mirabilis infection and subsequent encrustation.
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