Ultrastructural microbial ecology of infection-induced urinary stones.

With advanced techniques of scanning and transmission electron microscopy we studied the ultrastructural ecology of bacteria associated with struvite calculi on catheter surfaces, and in the bladder, ureter and renal pelvis. These detailed morphological data indicate that the interstices, core and external surface of such struvite aggregates contain large numbers of bacterial cells that grow as microcolonies and thick biofilms within extensive fibrous organic matrices. These bacterial cells and their secreted products (glycocalyx or biofilm matrix) appear to provide initial foci for crystal development and aggregation of crystals to form macroscopic struvite stones. The protective glycocalyx-enclosed microcolonial mode of bacterial growth also may explain the relative resistance to antibiotics observed in bacteria associated with infection stones.