A patient of Acute lymphocytic leukaemia with fever and neutropenia develops diarrhoea after administration of amoxicillin therapy, which of the following organism is most likely to be the causative agent: (A) Salmonella typhi, (B) Clostridium difficile, (C) Clostridium perfringens, (D) Shigella flexneri
Answer is B. Clostridium difficile causes acute colitis with bloody diarrhea and pseudomembranous colitis. A common cause of nosocomial diarrhea. The disease follows the use of broad-spectrum antibiotics like clindamycin, ampicillin, amoxicillin, or fluoroquinolones to which it is resistant. Exotoxin A and B involved in the pathogenesis. An oppounistic organism that causes disease only when the normal mechanism is altered. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 270