Continuous fever from last 25 days.

Hi, my dad had hus cabg doen on 9th march 2017 he was doing very good in hospital as well as in icu and at home but when we went for his routine check up on 22nd march some medicine s were stoped after 2 days he started getting a temperature that is 99-100 we informed our doctor he told us to get blood and urine culture done urine culture came postive with two bacterias one of them was highly resistant to many antibiotics our sergion sad to take linospan 600 and furadantin 200 twice daily and thrice daily respectively and fever still dint stoped he ordered a culture in his hospital for the urine we got it done it came negative then he continued the medicine for a week but then too fever use to come that is 99-99.5 then he again asked us to get a urine culture done this time again the culture came negative for the urine . We tried stopping his combiflame which is one at night daily and the fever was not there for two days but again it came back and we have to start the combiflame