Urinary tract infections in babies and children are quite common and easily checked by a 5 day course of antibiotics(depending upon which antibiotic is chosen.). The danger of repeated infections is that the kidney may get involved and this is indeed a serious complication and hence for resistant or repeated attacks, long term antibiotics "may " be used.
"Surely this is way too long for anyone to be on antibiotics never mind a five month old baby? "
You make a very good point erin and using long term antibiotics to prevent complications must be weighed against the development of resistance to the antibiotic which clearly would defeat the object of the treatment.
Some Pediatricians DO use long term antibiotics, some DON'T , it being, like most things in medicine,a matter of opinion.
I would want a very erudite and compelling explanation before I would allow my 5 month old baby to be treated with long term antibiotics.
There may well be a good reason.