BK infection is an important cause of graft dysfunction and graft loss after renal transplantation. It has been widely accepted that emergence of BK virus correlates with the more potent immunosuppressive agents used to lower acute rejection rates. In contrast to other opportunistic infections after transplantation, for which routine prophylactic agents are administered, there is no effective agent for the prevention of BK infection. Some data, however, suggests that quinolone antibiotics such as ciprofloxacin may have activity against BK virus. This has led us to investigate whether routine, short-term ciprofloxacin administration post-transplant can lower the incidence of BK infection.

BK virus is a member of the virus family polyomaviridae ("polyoma"). The virus, which can manifest as a viral nephritis, was first described in a renal transplant recipient in 1971, however it was not until the past decade that infection with BK virus became known as an important contributor to graft dysfunction and graft loss after renal transplantation. It has been widely accepted that emergence of BK virus correlates with the more potent immunosuppressive agents currently used to lower acute rejection rates. In contrast to other opportunistic infections after transplantation, for which routine prophylactic agents are administered, there is no effective agent for the prevention of BK infection, nor is there an effective agent for treating BK infection once it occurs.

Ciprofloxacin is a well known anti-infective agent in the fluoroquinolone class of antibiotics. It is most active against gram-negative enteric pathogens, and is commonly used for a variety of infectious indications.

Though classified as antibacterial agents, fluoroquinolones have been suggested to exhibit anti-BK viral effects by interfering with helicase activity of the BK virus large T antigen. Ciprofloxacin has been shown in previous studies to reduce urine BK viral load, and BK-associated hemorrhagic cystitis in the stem cell transplant population. Ciprofloxacin has also been associated with a lower incidence of BK viremia in one retrospective study in kidney transplant recipients. Based on these reports, the investigators hope to find a reduction BK viremia and BK nephropathy using a prospective, randomized study design.

Inclusion Criteria:

• Male or female subjects over the age of 18 years
• Recipients of a primary or repeat renal allograft either alone (from a deceased or living donor) or as a dual-kidney transplant
• Signed informed consent form prior to any research assessment

Exclusion Criteria:

• Patients with known severe allergy to ciprofloxacin
• History of tendon rupture or tendinitis
• Use of antiarrythmic drugs known to prolong the QT interval such as class IA antiarrhythmic drugs (e.g. quinidine, procainamide, disopyramide), class III antiarrhythmic drugs (e.g. amiodarone, sotalol)
• Patients with history of previous non-renal transplantation
• Recipients administered rituximab within one year prior to transplantation, or recipients expected to receive rituximab as part of desensitization strategy or for the presence of historical donor specific antibodies
• QTc interval interval of greater than 500 msec on admission or post-operative EKG
• BK nephropathy with previous transplant
• BK viremia on admission
• Any condition present during the initial transplant hospitalization that in the investigator's judgment would increase the risk associated with participation in the study

Analysis performed on IIT patients (all randomized patients)

Adverse events were collected out through 4 months (3 months of study drug administration + 1 month post- administration). Patients were asked during clinic visits to report any potential ciprofloxacin adverse event from a list of common adverse effects. Additional AEs were collected if reported by clinician. Graft loss and patient death were additionally collected out through 1 year