Repeated fever. To find the root cause.

My father aged 73 years has been Asthmatic for ages and four years back he underwent bilateral orchiectomy for Prostrate cancer. Since then he developed cellulitis in the legs with his skin in the legs becoming dark and scaling off and with liquid oozing out from the lower limb. With medication the liquid oozing out has stopped and time and again he develops fever every 2 months which persist for 2 days with antibiotics (Ornidazole - Oflaxin or Glevo). The doctor at time brings the fever from 102 degrees Amikacin and fevastine injection and recommends the above said antibiotics for 2-3 days. I would like to understand if the fever is due to his cellulitis infection and whether the doctor is proceeding in the correct lines and what can be done to prevent this 2 day fever every alternate month. Pls advise keeping in mind that he has mobility problems and requires help in moving about as well.Pls also suggest any tests that may be required to find the root cause.