My Dad Has A Streptococcus Mitis Infection And Has Had

My dad has a Streptococcus Mitis infection and has had the bearing replaced in his knee replacement two weeks ago. His CRP was at 23 and has come down since his operation to 16, then 11, then 5, then 3.9. He is on strong IV antibiotics. However over the last five days his CRP has gradually crept up to 5.2. The consultant is concerned and is thinking of looking at the knee again to check for further infection. However for the last 5 days or so my dad has had a really heavy cold and cough. Is it feasible that the increase in CRP during the time he has had the cold/cough could be down to that or is that unlikely? Can the CRP test actuall identify what is causing the inflammation? Many thanks.