A patient of Acute lymphocytic leukemia with fever and neutropenia devlops diarrhoea after administration of amoxicillin therapy, which of the following organism is most likely to be the causative agent ?

It is a typical presentation of CDAD (Cl. difficle associated diarrhoea). MC antibiotics causing CDAD - clindamycin, ampicillin and cephalosporins. Antibiotics altered the normal intestinal flora which allows overgrowth of non-pathogenic organism. This called as superinfection. Superinfection also occur by candida albicans, resistant staphylococci, Proteus and Pseudomonas. Superinfections are common when host defence is compromised as in steroid therapy, Leukemia and other malignancies treated with anticancer drugs, AIDS, agranulocytosis, Diabetes.