What Causes Increase Of Pus Cells In Stools Despite Metronidazole Intake?

Hi! I would like to ask about my father s fecalisis. Last February 27, 2015 his fecalysis shows pus cells of 8-10 hpf, many RBC, moderate bacteria 4-6 hpf E. histolytica cyst and he was advised to increase fluid intake and metronidazole tab 500mg TID . March 6, he had his test repeated with results of 10-12 hpf pus cells, many RBC, moderate bacteria and 4-6hpf cyst e histolytica. his metronidazole was extended until he completed his 15 day but there was no prognosis. He had his fecalysis again this morning and his results were 15-20 hpf pus cells, many RBC, many Bacteria and 3-5 e. histolytica. my father still experiences LBM, he described to me that he is still excreting loose-oily stool with foul smelling odor. Should his metronidazole be given to him via IV? I am getting worried. He is 71.