How Can A Liver Abcess Be Treated?

Hy. My father is having liver abcess problem since 4 weeks . It s pyogenic . Giving combination of sulbactrum and cefoperazone 2gm BD and metronidazole 500mg TID since last 21 days intravenous. If we remove treatment then again fever starts .but when again continue then fever off. What should we do? Abcess size 6cm . It s on left lobe of liver . Doctor not recommend aspiration because it s near to heart. But above treatment is reducing abcess size round about 30% . Should we continue same treatment more till 28 days ? Patient show weakness . TLC value 12. and HB level 9.5 ,all RFT and LFT reports are clear but only thing is low A/G ratio 0.6, BUN level is also low as normal level. Please segust best recommendation.thanks.