The significance of the difference in bacterial adherence between bladder and ileum using rat ileal augmented bladder

Intestinal segments are frequently used in the reconstruction of the urinary tract. Chronic bacteriuria is frequently observed in these patients, but the reason is not clearly understood. Therefore, we studied the difference in bacterial adherence between bladder and ileum using the rat ileal augmented bladder model to investigate the cause of chronic bacteriuria.

Augmentation of the bladder using ileum and a sham operation were performed under sodium pentobarbital in 102 and 10 Sprague-Dawley rats, respectively. At three months after the operation, urinary pH and plasma concentration of sodium, chloride and potassium were measured and urinary culture was done. Urovirulence factors of Escherichia coli aspirated from augmented bladder were detected by polymerase chain reaction (PCR). Five to six rats with negative urinary cultures after the augmentation were used for each experimental cystitis. E. coli with type I pili aspirated from augmented rats and three clinically isolated strains of E. coli, C5 (type I pili, aerobactin), C92 (type I pili, aerobactin, P fimbriae), and C189 (type I pili, aerobactin, P fimbriae, CNF), were transurethrally inoculated into the augmented bladder of rats. Fourteen days after inoculation, rats were sacrificed and colony-forming units (CFU) per mg. of tissue of bladder and ileum were measured.

After operation, urinary pH and the serum level of chloride in all augmented groups were higher than those of the controls. Bacterial colonization was observed in 56 of 89 rats. Most of them were E. coli having only type I pili as a virulence factor. In contrast, the sham operated group revealed no bacterial colonization. In experimental cystitis, E. coli with only type I pili aspirated from augmented rats and E. coli C5 were clearly adhered to ileum rather than to bladder, but E. coli C92 and C189 showed no significant difference with respect to adherence to the two tissues. In experimental cystitis II, E. coli C5 with D-mannose were washed out in 3 of 5 rats by 14 days, while E. coli C5 without D-mannose were not washed out in all rats by 14 days.

These results suggested that the difference in bacterial adherence due to urovirulence factors, especially type I pili, is one of the main causes of asymptomatic bacteriuria after urinary reconstruction.