Final answer:
Reinfection in UTIs occurs when the infection reoccurs after initial treatment. It is challenging to treat because bacteria can form protective biofilms that make them resistant to antibiotics.
Step-by-step explanation:
Reinfection in Urinary Tract Infections (UTIs) refers to the recurrence of the infection caused by the same bacteria after it has been treated and cleared. It can happen when the original infection was not completely eradicated or when new bacteria are introduced into the urinary tract. It is difficult to treat because bacteria can form biofilms, which are protective layers that make them more resistant to antibiotics and harder to eliminate.