Firstly
Stick to boil bake it peel it or forget it!
Doesn't always work and hasn't for me this time.
You are talking about ciprofloxallin. I wouldn't take as a preventative, but if you get bacterial delhi belly it should clear it in 6-12 hours. You need 500 mg tablets taken twice daily for at least 5 days.
If it doesn't clear it, you may have picked up a parasite (Amoebic dsentry, Giardia etc) so seek medical advice. Good privae doctors here.
Hope this helps