To study the process of formation of renal calculi, 85 patients with calculi were divided into 6 groups according to the chemical composition of surgically removed stones. Isolation and identification of the embedded microorganisms in the cores of stones were carried out. It was found that Pseudomonas was the bacteria that infected the interstices and cores of the smost stones. E. coli (non - urease producer) and Staphylococcus epidemidis came next.
Proteus mirabilis was found to be the bacteria embedded in the cores of the struvite stones in group 6( Ca Ox Ca P- MAP-U stones), as urea - splitting organisms. Klebsiella was not isolated from any stones in spite of the fact that it is urease producer. Urine protein, immunoglobulin fractions and the amount of proteins in the stone matrix were determined. It was noticed that the high level of proteins and immunoglobulins in urine samples may reflect an inflammation or infection in many cases of the studied groups compared to the normal subjects. This was particularly noticed in the groups having struvite stones with the presence of high protein content in stone matrix, associated with high bacterial infection . In all types of stones that contain proteins it was found that the embedded bacteria were protease producers. These findings may imply that the embedded bacteria, its excreted products and the protein contents in the stone matrix may be acting as a precipitant and as connective substances for the crystals to grow and aggregate.