[Colonization types of Escherichia coli in experimental urinary tract infection in compromised mice treated with...

We studied the experimental urinary tract infections (UTIs) on compromised mice with Escherichia coli to elucidate the effects of three factors (bacterial strains, doses of hydrocortisone, infectious periods) on the bacterial colonization in the bladders. We selected three strains from the stock of E. coli isolated from the urine or feces of patients with lower UTI, because each of the three strains showed a tendency in colonization in previous experiments: One strain, which was named H70, showed a relative slight and intracellular colonization; the H99, an extracellular and the K88, both intracellular and extracellular growths which were large. The rate of bacterial microscopic recovery from the bladders of mice inoculated strains H70, H99 and K88 were 25.0, 41.7 and 79.2% respectively. And the recovery from the mice inoculated cortisone, 0, 2, 4 and 8 mg/mouse were 38.9, 55.6, 55.6 and 44.4% respectively. The detections of various colonizations at 3, 6 and 24 hr after the bacterial inoculation were that extracellular types were 45.8, 20.8 and 20.8%, intracellular types were 4.2, 16.7 and 12.5%, simultaneous colonizations were 4.2, 16.7 and 4.2% and the detections of at least one of them were 54.2, 54.2 and 37.5% respectively. Thus, the global findings were that extracellular growth of the bacteria were predominant at first, then the bacteria invaded the mucosal cells and the intracellular bacteria stayed after the voiding of extracellular bacteria. Intracellular colonizations seemed more strongly interacting with hosts than extracellular types, because cortisone enhanced the intracellular colonizations more strongly than the others. However, it seemed that urinary tract infections were not simple events but the results of the interactions of the bacterial strains and hosts, because the locations and degrees of the bacterial colonization and the effects of hydrocortisone on them were different in each bacterial strain and infectious period.