OBJECTIVE To study the role of outer membrane protein T (OmpT) in the pathogenesis of uropathogenic Escherichia.coli. METHODS In cultured human bladder epithelial cell line 5637, we examined the adhesion ability of wild-type (CFT073), ompT gene knockout (COTD), and revertant (pST) strains of E.coli to the cells and the extracellular matrix (ECM). The expressions of the adhesion gene iha and virulence gene iroN were detected by real-time PCR. Murine models of urinary tract infection with the 3 strains were established to evaluate the bacterial burden of the bladder and kidney tissue and bacterial counts in blood. We also detected the expressions of interleukin-6 (IL-6) and IL-8 in the bladder and kidney tissues of the mice. RESULTS The COTD strain showed a significantly lower cell adhesion rate than CFT073 strain [(4.62∓0.39)% vs (8.81∓1.13)%, P<0.05] with also a lower ECM-adhesion rate [(4.95∓0.59)% vs (8.85∓0.79)%, P<0.05]. The mRNA expressions of iha and iroN in CFT073 strain were 2.1 and 3.8 times that of COTD strain. In the mouse model, the mean bacterial load of CFT073 strain in the bladder tissue was 6.36∓0.06, significantly greater than that of COTD (6.01∓0.07) and revertant (6.29∓0.06) strains (P<0.05); the bacterial load of CFT073 strain in the kidney tissue was also significantly higher than that of COTD strain (6.25∓0.05 vs 5.87∓0.06, P<0.05). In mice infected with the wild-type, knockout, and revertant strains, the detection rates of IL-6, which were identical to those of IL-8, in the inflammatory bladder and kidney tissues were 60%, 12.5%, and 50%, respectively. CONCLUSIONS OmpT may regulate the expression of the adhesion gene iha and the transferrin gene iroN to affect the adhesion of uropathogenic E.coli to host cells.