Oral OM-89 in combination with antibiotics prevents recurrent infection in a mouse model of urinary tract infection

Urinary tract infection (UTI) is a very common infection. Approximately 25% of all women will experience recurrent infection, defined by 2 UTI in 6 months or 3 UTI in a 12 month period. Recurrent infection is thought to be due in part to the development of local bacterial reservoirs in the bladder after an infection. These reservoirs are undetected by the host immune system and may re-emerge after resolution of the primary infection. Frequently, recurrent UTI require repeated antibiotic use, leading to the development of resistance, and negatively impacting the quality of life of the patient. Given the rise in multidrug resistant uropathogens, treatments that do not rely upon antibiotics are urgently needed for this patient population. We assessed the capacity of a lyophilized E. coli extract, OM-89(R), as a preventive measure to reduce the incidence of spontaneous recurrence in a mouse cystitis model. Administration of OM-89 per os after the initiation of an acute UTI significantly reduced the number of spontaneous recurrent UTI in female mice over a 1 month follow-up period only when the animals were also treated with antibiotics. Protection against recurrent UTI arose quickly and without changes in any adaptive immune response parameter measured, ruling out a role for OM-89 in augmenting adaptive immunity to protect against spontaneous recurrent UTI in the first month of use.