UTI's and D-Mannose

Hi everyone. Any advice would be appreciated. I am getting what seems like permanent UTI’s. I catheterise twice a day and follow all the correct procedures and cleanliness. I also take cranberry tablets and drink cranberry juice. I try to keep my fluid intake up, so doing everything I’m supposed to. I don’t want to go on a permanent dose of antibiotics and have read with some interest about D-Mannose capsules. Just about at the end of my tolerance. Any ideas? Linda x