IRF3 and bacterial urinary tract infection: To examine if the IRF3-dependent immune response discriminates uropathogenic E. coli from non-pathogenic bacteria, we inoculated wt and Irf3−/− mice with the prototypical asymptomatic bacteriuria strain E. coli 83972, which lacks functional UTI-associated virulence factors, including P fimbriae [26], [27], [28], [29].