Bacterial interference in mixed infection in the rat bladder.

Interaction between Escherichia coli and Pseudomonas aeruginosa was studied in chronic bladder infection made in male Wistar rats by implanting a knotted silk thread holding organisms into the bladder. Strains isolated from patients were used. The number of organisms in bladder urine was measured 1 week after the inoculation. When E. coli and P. aeruginosa were inoculated simultaneously, P. aeruginosa grew less well than when inoculated alone. When P. aeruginosa was inoculated into the bladder colonized with E. coli, P. aeruginosa was almost always unable to grow in the bladder, while E. coli inoculated into the bladder colonized with P. aeruginosa was able to grow there in many animals. Bacteriocin activity had nothing to do with the results. These results indicate that E. coli interferes with the growth of P. aeruginosa in mixed infection in the bladder.