Hi,
Welcome to health care magic,
If your father is being treated for UTI with the help of antibiotics (collistin injection) for 7 days course then here is my comments on that.
It could be severe
urinary tract infection (if your urine reports is showing plenty of pus cells).
Anyway,your father need to be detailed medical history and thoroughly clinical examination by a
urologist to get ruled out any other
kidney pathology or retrograde infection.
He might require antibiotics (quinolones specially
levofloxacin in high dose or amixocillin with
clavulanic acid) for full course for at least 15 days to combat urinary infection completely with other symptomatic treatment like pain killers,anti-inflammatory with syrup citralka 2TSF three times daily with plenty of water intake.
Better not to skip any medicines and preferably complete all the medications especially antibiotics for at lest 15 days.
However,it would be better to consult to urologist immediately and take complete course of treatment.
Regards,