@rosemariewalters, here is an article that helps explain more about D-mannose.
- Can D-Mannose Treat or Prevent UTIs? https://www.healthline.com/health/d-mannose-for-uti

People have used it both for prevention and treatment of urinary tract infection. But you're quite right that antibiotic still play an important role in clearing UTI infections. Although D-mannose might help treat a UTI for some people, it’s important to follow medically proven methods of treatment to prevent the development of a more serious infection. As always, consult with your doctor.