Researchers discovered a concerning association between bacteremia and probiotic use, particularly with Clostridium butyricum (C. butyricum) MIYAIRI 588. Whole-genome sequencing revealed that all C. butyricum bacteremia strains were probiotic derivatives. Out of 6,576 cases of positive blood cultures, C. butyricum was detected in only five cases, all derived from probiotics. The study underscores rare but serious adverse events linked to probiotics, advocating cautious prescribing practices, especially for hospitalized patients.