Repeat Clostridium difficile Testing.

A 28-year-old man presented with abdominal pain and diarrhea (10-12 Bristol type 7 stools per day; Bristol scale range, 1-7 [1, separate hard pieces; 7, watery stool])1 after completing a course of azithromycin for pneumonia. He was diagnosed with Clostridium difficile infection (CDI) with a positive stool polymerase chain reaction (PCR) for the toxin B (tcdB) gene. Laboratory studies showed unremarkable results (Table 1). He was successfully treated with a 10-day course of oral metronidazole, and his bowel movement pattern returned to its baseline of 2 to 3 Bristol type 4 stools per day. Six weeks later, he presented with abdominal discomfort for 3 weeks relieved by bowel movements associated with increased stool frequency (4-5 Bristol type 4 stools per day). Vital signs and physical examination were unremarkable and a repeat stool test for C difficile toxin PCR was positive.