This is a research study that aims to determine if antibiotic bladder instillations (placing an antibiotic directly into the bladder) over several sessions at the office is a good option to prevent recurrent urinary tract infections, in comparison with oral suppression therapy (taking daily antibiotics in the form of pills by mouth). Oral antibiotic suppression therapy is currently the most common treatment route for recurrent urinary tract infections in post-menopausal women. The bladder antibiotic instillation may overcome the disadvantages of oral suppression therapy such as antibiotic resistance, certain side effects, and recurrence of infections after finishing the treatment course.

In this study, the investigators aim to determine the effectiveness of intra-vesical antibiotic instillations for the prophylactic treatment of recurrent urinary tract infections in menopausal women in comparison with oral suppressive therapy. This is a parallel un-blinded randomized-controlled trial. the investigators will randomize post-menopausal women with recurrent urinary tract infections to either receive 6-8 intra-vesical antibiotic instillations at the office or to receive 3 months of oral antibiotic suppressive therapy.

In the bladder instillation arm, based on the participant's allergy and antibiotic resistance profile, one of the following three antibiotics will be instilled intravesically via a latex free BARD® 12 French Foley catheter for a total of 6-8 instillations (2 instillations/week) according to the Atlantic Health System Urogynecology Division antibiotic bladder instillation standard protocol:

• Amikacin-30 mg in 60 ml of sterile water
• Gentamycin-80mg in 60ml sterile water
• Tobramycin-80 mg in 100 ml of sterile water

In the antibiotic oral suppression therapy arm, one of the following routinely used antibiotics will be prescribed for a total of 3 months according to the American Urogynecology Society Guidelines and based on the participant's allergy and antibiotic resistance profile:

• Trimethoprim daily (100 mg)
• Trimethoprim/sulfamethoxazole daily (40 mg/200 mg)
• Trimethoprim/sulfamethoxazole every 3 days (40 mg/200 mg)
• Nitrofurantoin monohydrate/macrocrystals daily (50 mg)
• Nitrofurantoin monohydrate/macrocrystals daily (100 mg)
• Cephalexin daily (125 mg)
• Cephalexin daily (250 mg)
• Fosfomycin every 10 days (3 grams) All medications used in this study are approved by the FDA to treat urinary tract infections.

Participants will be followed for total of 3 months after finishing either treatment course by only reviewing their medical records to collect data regarding development of urinary tract infections after treatment.

Primary endpoint/outcome:

• To compare the number of women developing urinary tract infections during the 3 months following treatment between the two groups.

Secondary endpoints/outcomes:

• To compare the rate of antibiotic resistance of isolated pathogens after intravesical antibiotic instillation vs. oral antibiotic suppressive therapy
• To compare side effects of the two treatment modalities

Inclusion Criteria:

• Post-menopausal women with recurrent urinary tract infections (2 infections in a 6-month period or at least 3 infections in a 1-year period)
• Receiving estrogen vaginal therapy for 1 month prior to enrollment
• Able to come in to the office twice weekly for 3-4 weeks
• English speaking
• No allergy to at least one of the three antibiotics used for bladder instillations and at least one of the four antibiotics recommended for oral suppressive therapy.
• No uro-pathogen resistance to at least one of the three antibiotics used for bladder instillations and at least one of the four antibiotics recommended for oral suppressive therapy.

Exclusion Criteria:

• Allergy to all study antibiotics (Gentamicin, Tobramycin, Amikacin, Trimethoprim/sulfamethoxazole, Fosfomycin, Nitrofurantoin and Cephalexin)
• Recent Urine culture with pathogens resistant to all study antibiotics (Gentamicin, Tobramycin, Amikacin, Trimethoprim/sulfamethoxazole, Fosfomycin, Nitrofurantoin and Cephalexin)
• Renal failure (Creatinine clearance <30ml/min)
• History of urinary retention
• History of genitourinary structural abnormalities