Cells and Materials


A physical model of the bladder has been used to study the process of urinary catheter encrustation. Techniques have been devised for the preparation of sections through these encrustations in situ on the luminal surfaces of catheters and for mapping the distribution of calcium and magnesium in the biofilms. Transmission electron microscopy on these sections showed struvite-like crystals lying in the matrix and in direct contact with the catheter surface. Calcium phosphate ("bioapatite") was distributed throughout the film and many of these amorphous particles appear to have cells at their cores. Freeze-substituted sections of biofilms also showed electron dense materials around cell-like shapes and X-ray mapping and X-ray scanning transmission microscopy on the catheter biofilms also indicate that mineralization occurs around the bacterial cells.

These observations suggest that in catheterized bladders infected by Proteus mirabilis, bacteria and crystals formed in the urine, adhere to the catheter. Further colonization and growth of the cells on the catheter and crystal surfaces produces the alkaline biofilm which provides the conditions for continued encrustation. The binding of crystals directly onto the catheter and the subsequent bacterial colonization of these crystals has implications for attempts to prevent encrustation by manufacturing catheters from biomaterials impregnated or coated with antibacterials.