A stool culture is used to identify the pathogenic bacteria responsible for persistent diarrhea. A stool culture is often combined with testing for other pathogens that also cause diarrhea (eggs and parasites). The most common varieties of bacteria in North America are tested for, including Campylobacter (raw or undercooked meat and poultry), Salmonella (raw eggs, poultry and vegetables, reptile pets), Shigella (contaminated food and water), Yersinia (raw or undercooked pork) and the E. coli serotype O157 (responsible for hamburger disease or barbecue syndrome). A stool culture cannot be used to identify C. difficile bacteria. A specific order to test for the C. difficile antigen and toxin is required. To increase the chances of identifying the bacteria responsible for diarrhea, a stool culture is often repeated on 2 or 3 stool samples collected on different days.
A negative result indicates that the bacteria listed on the report are probably not responsible for the diarrhea. A positive result for one of the bacteria tested for indicates that that bacterium is probably responsible for the diarrhea. When a positive result is obtained, an antibiogram indicating the bacteria’s sensitivity or resistance to certain antibiotics helps the physician choose the most appropriate treatment.