Respected user, hi I evaluated your query thoroughly.
* Recurrent UTI have vivid reasons as 
- resistance to particular antibiotic
- different causative organisms 
- load of infection 
- improper previous treatments
- inadequate hydrations with altered urinary pH
- associated conditions as 
Diabetes or others
- sexually transmitted disease
- immunocompromised states
- improper hygiene
* Clearing infection in how many days depend upon the bacterial 
   susceptibility to the antibiotic , host response , load of infection , level of
   hydrations etc. may be cleared in 3 days if minor but may take more if
   moderate to severe infection.
* After any No. of doses of 
Levofloxacin it remains in blood stream for 6-8
   hours only ( not for 3-5 days )
Hope this clears your doubts
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Wishing you healthy life ahead.
Welcome for any further assistance.
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