Probiotics are defined as live microorganisms that when administered in adequate amounts confer a health benefit on the host [1]. The term probiotic encompasses various subcategories, including probiotic drugs, probiotic foods (such as foods, food ingredients, and dietary supplements), direct-fed microbials (probiotics for animal use), and designer probiotics (genetically modified probiotics). In the United States, probiotic products are predominantly marketed as foods or dietary supplements to the general population, including those who are generally healthy [2]. Probiotics have recently become widely used in clinical practice, but there have been numerous reports of bacteremia associated with probiotics containing Lactobacillus and Bifidobacterium [3,4]. The Clostridium butyricum strain MIYAIRI 588 was discovered in 1933, and production began as a pharmaceutical product in 1940. It is recognized for its production of butyrate and has garnered approval for human use in Europe, owing to its proven safety and efficacy. The positive impact of Clostridium butyricum strain MIYAIRI 588 on the human colon may be attributed to its ability to increase the thickness of the mucosal layer and regulate mucosal immune cells. It has been used for preventing or treating antibiotics-related diarrhea or infected enterocolitis [5]. Although there have been a few reports of Clostridium butyricum bacteremia in patients taking probiotics [6,7], risk factors for bacteremia are unknown. Here, we determined risk factors for C. butyricum bacteremia by means of a literature review and three cases treated in St Luke's International Hospital.