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Observations of the ultrastructure of infected kidney stones
R J McLean1, J C Nickel, T J Beveridge
1Department of Microbiology, University of Guelph, Ontario, Canada.
Abstract:
Struvite stones are formed as the result of urinary tract infection by urease-producing bacteria. Ultrastructural examination of calculi removed from a patient revealed bacteria incorporated throughout the stone matrix. Exopolysaccharide stained by ruthenium red was associated with most of the bacteria, but it represented only a small portion of the organic matrix in the stone. Localised deposits of calcium and phosphorus, components of carbonate-apatite, and magnesium, a struvite component, were detected in close proximity to the cells. Histochemical examinations revealed that several of the gram-negative bacteria within the stone matrix possessed high levels of urease activity. We propose that bacterial slime production, intimately involved in the initiation of stone matrix deposition, is less prominent in mature stones because of the increased incorporation of host-derived mucoproteins and mucopolysaccharides.
Insights
Struvite stones form from urinary tract infections by urease-producing bacteria. Bacterial slime and host mucoproteins contribute to stone matrix formation, influencing its composition.
Area of Science:
- Urology
- Microbiology
- Biochemistry
Background:
- Struvite stones result from urinary tract infections (UTIs) caused by urease-producing bacteria.
- These stones are primarily composed of magnesium ammonium phosphate (struvite).
- The role of bacterial byproducts and host factors in stone matrix formation is not fully understood.
Purpose of the Study:
- To investigate the ultrastructural and histochemical characteristics of struvite calculi.
- To elucidate the contribution of bacteria and their products to the organic matrix of struvite stones.
- To understand the transition in matrix composition during stone maturation.
Main Methods:
- Ultrastructural examination of human struvite calculi using electron microscopy.
- Histochemical staining (e.g., ruthenium red) to identify bacterial exopolysaccharides and matrix components.
- Detection of mineral components (calcium, phosphorus, magnesium) using localized elemental analysis.
- Assessment of urease activity in bacteria within the stone matrix.
Main Results:
- Bacteria were observed incorporated throughout the struvite stone matrix.
- Bacterial exopolysaccharides were present but constituted a minor fraction of the organic matrix.
- Localized deposits of calcium, phosphorus, and magnesium were found near bacterial cells.
- Gram-negative bacteria within the stones exhibited significant urease activity.
Conclusions:
- Urease-producing bacteria are central to struvite stone formation.
- Bacterial slime production is crucial in initiating stone matrix deposition.
- Mature struvite stones incorporate more host-derived mucoproteins and mucopolysaccharides, reducing the relative prominence of bacterial slime.