In vivo transfer of an R-plasmid in a urinary tract infection model

Spontaneous loss of antibiotic-resistant plasmids transferred to Escherichia coli in experimental chronic bladder infection

BACKGROUND

We investigated whether Escherichia coli that has been transformed with antibiotic-resistant plasmids spontaneously loses the plasmids while infecting the rat bladder.

METHODS

A nontransmissible antibiotic-resistant plasmid was transferred to a clinically isolated strain of E. coli. A knotted thread holding the strain was implanted into the bladder of male Wistar rats. One or 4 weeks later, the total number of bacteria and that of plasmid-carrying bacteria were measured in the bladder.

RESULTS

When plasmid-carrying E. coli alone was inoculated, most of the plasmid-carrying E. coli were replaced with plasmid-free E. coli. When plasmid-carrying and plasmid-free E. coli were simultaneously inoculated, this replacement was accelerated.

CONCLUSION

These results suggest that E. coli carrying antibiotic-resistant plasmids spontaneously lose the plasmids as time passes, and thus become sensitive to antibiotics.

Experimental prostatitis in nonhuman primates: II. Ascending acute prostatitis

Bacterial prostatitis is a common cause of urinary tract infection in males, but little is known of its pathophysiology. To study this, we developed a nonhuman primate model using a wild-type clinical isolate of Escherichia coli. Primates have a prostatic anatomy that is similar to humans, which makes them ideal as an animal model of this disease. The monkeys had a urethral inoculation of this organism and were then followed with urine, blood, and semen cultures, white blood counts, and renal scans. They were sacrificed at from 10 days to 4 weeks, and their genitourinary tracts histologically examined. The prostatitis paralleled that reported in humans, and we conclude that the infection occurs by the ascending route. The organisms causing the infection in man do so in our primate model, and the histologic change is also the same. Thus, the primate model holds promise for studies to help us understand this disease.