Cytotoxic necrotizing factor type 1 (CNF1) is a 115-kDa toxin that activates Rho GTPases and is produced by uropathogenic Escherichia coli (UPEC). While both epidemiological studies that link CNF1 production by E. coli with urinary tract disease and the cytopathic effects of CNF1 on cultured urinary tract cells are suggestive of a role for the toxin as a UPEC virulence factor, few in vivo studies to test this possibility have been reported. Therefore, in this investigation, we evaluated the importance of CNF1 in a murine model of urinary tract infection (UTI) by comparing the degree of colonization and damage induced by three different CNF1-producing E. coli strains with isogenic CNF1-deficient derivatives. The data from single-strain challenge experiments with C3H/HeOuJ mice indicated a trend toward higher counts of the wild-type strains in the urine and bladders of these animals up to 3 days after challenge in two of three strain pairs. Furthermore, this difference was statistically significant at day 2 of infection with one strain pair, C189 and C189cnf 1 . To control for the animal-to-animal variability inherent in this model, we infected C3H/HeOuJ mice with a mixture of CNF1-positive and -negative isogenic derivatives of CP9. The CNF1-positive strain was recovered in higher numbers than the CNF1-negative strain in the urine, bladders, and kidneys of the mice up to 9 days postinfection. These striking coinfection findings, taken with the trends observed in single-strain infections, led us to conclude that CNF1-negative strains were generally attenuated compared to the wild type in the C3H/HeOuJ mouse model of UTI. Furthermore, histopathological examination of bladder specimens from mice infected with CNF1-positive strains consistently showed deeper, more extensive inflammation than in those infected with the isogenic mutants. Lastly, we found that CNF1-positive strain CP9 was better able to resist killing by fresh human neutrophils than were CP9cnf 1 bacteria. From these data in aggregate, we propose that CNF1 production increases the capacity of UPEC strains to resist killing by neutrophils, which in turn permits these bacteria to gain access to deeper tissue and persist better in the lower urinary tract.

Infection of rat prostates with cytotoxic necrotizing factor type 1 (CNF1)-positive uropathogenic Escherichia coli caused more inflammation-mediated morphological and histological tissue damage than did infection with isogenic CNF1-negative mutants. These striking differences occurred despite the finding that bacterial counts for the strain pairs were indistinguishable. We conclude that CNF1 contributes to E. coli virulence in a model of acute prostatitis. To our knowledge, the results of this study provide the first demonstration of a role for any uropathogenic E. coli virulence factor in acute prostatitis.Symptoms of prostatitis occur in up to one-half of all men at some time during their lifetimes, and these clinical manifestations are the most common source of urologic complaints in men younger than 50 years of age. Bacterial prostatitis, characterized by symptoms of urinary tract infection (UTI), accounts for 5 to 10% of all prostatitis cases. The primary etiological agent of bacterial prostatitis is Escherichia coli. Many of the disease-causing E. coli isolates express one or more of several virulence factors that include cytotoxic necrotizing factor type 1 (CNF1), hemolysin, and P fimbriae. Indeed, epidemiological studies have linked CNF1 with strains that cause prostatitis, as well as uncomplicated UTI in women. Specifically, Mitsumori et al. reported that 64% of prostatitis patient isolates were cnf 1 ϩ (18), and Andreu and colleagues found that the percentages of cnf 1 ϩ prostatitis, pyelonephritis, and cystitis patient isolates were 63, 48, and 44%, respectively (1). In accordance with the findings of Andreu et al., Terai and colleagues noted that 44% of E. coli isolates from patients with ascending urethral bacterial prostatitis were cnf 1 ϩ (27). CNF1 is a chromosomally encoded uropathogenic E. coli (UPEC) toxin that catalyzes the deamidation of the small GTPases RhoA, Rac, and Cdc42 (8,9,15,26). Deamidation of the GTPases renders these proteins constitutively active, an occurrence that in most cells leads to formation of actin stress fibers, lamellipodia, and filopodia. HEp-2 cells, which have been used as the prototypic cell line for evaluation of CNF1 toxicity, not only display actin stress fibers but also become multinucleated (3,6,24). Moreover, CNF1 has been reported previously to mediate a spectrum of additional phenotypic effects on cultured cells that include enhancement of phagocytosis in epithelial cells (5, 7) and reduction of CR3 receptordependent phagocytosis in monocytes (2, 5, 7). CNF1 also inhibits wound repair in T24 bladder cells and Hs 738 fibroblast cells (11), kills 5637 bladder cells through an apoptotic mechanism (17), effaces the brush border of T84 cells, and decreases the degree to which polymorphonuclear leukocytes migrate across a monolayer of those intestinal cells (10). Thus, CNF1 affects a variety of cellular functions in vitro, presumably through activation of the Rho GTPases.Recently, we determined that CNF1 produced by UPEC contributes to the virulence of those org...