Bacterial and crystal adherence to the surfaces of indwelling urethral catheters.

Bacterial and crystal adherence to the surfaces of indwelling urethral catheters was investigated by scanning electron microscopy and immunofluorescence method in relation to microbiological examination. Gram-negative bacteria were isolated more frequently than gram-positive bacteria in urine and catheter cultures. Microorganisms and crystals frequently were associated with fibrillar material, some of which was considered to be fibrin. On the surfaces of catheters indwelling for more than 1 week bacteria often were embedded in an amorphous matrix. It was believed that the thick coherent matrix adherent to the catheter served as a protected reservoir of microorganisms that persisted despite antimicrobial chemotherapy. Additionally, urease-producing bacteria attached to the catheter could have an important role in the development of calculous incrustation.