A 52-Year-Old Man Comes to the Physician Because of a 4-Day

A 52-year-old man comes to the physician because of a 4-day history of nonbloody, watery diarrhea that is associated with nausea and cramping lower abdominal pain. He says that the diarrhea is particularly foul smelling. There has been no change in his diet. Last week, he was treated with oral ciprofloxacin for a urinary tract infection. Laboratory studies show leukocytosis, and results from a stool specimen return positive for Clostridium difficile toxin genes by polymerase chain reaction.  Three days later, one of the nurses who cared for the patient at the nursing home is admitted with diarrhea and is found to have C difficile infection.  However, the other nurses who also took care of the patient are asymptomatic and do not develop the infection.  If all the nurses were similarly exposed to C difficile, which of the following is the most likely reason that the asymptomatic nurses did not develop the infection?

A) Adequate pancreatic enzyme secretion
B) Intact cell-mediated immunity
C) Preformed antispore immunoglobulins
D) Preserved intestinal microbiome
E) Rapid gastrointestinal transit and expulsion of spores