Repeated USMLE Questions Step 1-302

A 60-year-old man visits the clinic due to profuse watery diarrhea and left lower abdominal colicky pain for the last 6 hours. Upon taking history, the patient claims that he is taking broad spectrum antibiotics for acute bronchitis.

Which is the most likely causative organism for the patient’s new symptoms?

A- Clostridium botulinum

B- Clostridium butyricum

C- Clostridium difficile

D- Clostridium histolyticum

E- Clostridium Septicum


Antibiotic-associated diarrhea is most likely caused by clostridium difficile. The relation of this organism to the use of certain antibiotics is not fully understood yet. Treatment of this condition is oral vancomycin. Other types of clostridia mentioned in the choices cause different pathological conditions i.e. botulism, general sepsis, etc.

The correct answer is C

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