Review Question - QID 214630

A 47-year-old woman presents to the emergency department with lower abdominal pain. She has had a fever and vague abdominal pain for 3 days, but today the abdominal pain became severe. Her temperature is 104.1°F (40.1°C), blood pressure is 95/65 mmHg, pulse is 108/min, and respirations are 20/min. On exam, she is found to have purulent vaginal discharge with cervical motion tenderness and bilateral adnexal tenderness. She is diagnosed with pelvic inflammatory disease and admitted for inpatient management with IV cefoxitin and doxycycline. Two days later her fever returns and she develops profuse, foul-smelling, watery diarrhea. The patient's nurse wears only a surgical mask into the room and takes a stool sample to send for analysis. One week later the patient is discharged and the nurse never develops symptoms. Which of the following is the reason the nurse did not become infected with the same diarrheal illness?