Stool cultures for nosocomial diarrhea: money down the drain?

The authors report on a modified “3-day rule” for limiting low-yield stool cultures obtained from hospitalized patients with nosocomial diarrhea. The modified rule addresses the two known weaknesses of the strict 3-day rule: immune-suppressed patients and nosocomial outbreaks of bacterial gastroenteritis. In addition, the modified rule addresses a third group of previously unidentified patients at risk of non-Clostridium difficile bacterial nosocomial diarrhea: patients older than 65 with comorbidity. The modified rule would decrease the number of stool cultures by half without missing any clinically significant cases. The authors recommend the modified 3-day rule as a way to “greatly reduce the laboratory burden of stool culture, yet provide rapid diagnosis for patients at increased risk of nosocomial bacterial gastroenteritis.”