Catheter-associated urinary tract infections (CAUTI) are the most common hospital-associated infections. Here, we report that bladder catheterization initiated a persistent sterile inflammatory reaction within minutes of catheter implantation. Catheterization resulted in increased expression of genes associated with defense responses and cellular migration, with ensuing rapid and sustained innate immune cell infiltration into the bladder. Catheterization also resulted in hypersensitivity to Enterococcus faecalis and uropathogenic Escherichia coli (UPEC) infection, in which colonization was achieved using an inoculum 100-fold lower than the ID 90 for infection of an undamaged urothelium with the same uropathogens. As the time of catheterization increased, however, colonization by the Gram-positive uropathogen E. faecalis was reduced, whereas catheterization created a sustained window of vulnerability to infection for Gram-negative UPEC over time. As CAUTI contributes to poorer patient outcomes and increased health care expenditures, we tested whether a single prophylactic antibiotic treatment, concurrent with catheterization, would prevent infection. We observed that antibiotic treatment protected against UPEC and E. faecalis bladder and catheter colonization as late as 6 hours after implantation. Thus, our study has revealed a simple, safe, and immediately employable intervention, with the potential to decrease one of the most costly hospital-incurred infections, thereby improving patient and health care economic outcome.