Researchers analyzing patients in the intensive care unit in Boston Children’s Hospital have found that probiotic bugs can cause bacteremia and acquired antibiotic resistance (Nat. Med. 2019, DOI: 10.1038/s41591-019-0626-9). In recent years, health-care providers have been increasingly giving probiotics to hospital patients when they are admitted. Beneficial bacteria can help protect against infections such as ventilator- associated pneumonia and sepsis. But some doctors have concerns that live bacteria may cause infections in patients with weak immune systems. A team led by Thomas J. Sandora and Gregory P. Priebe at Boston Children’s Hospital found that patients given Lactobacillus rhamnosus strain GG probiotics have higher rates of blood infection—1.1% compared with 0.009% for patients not given probiotics when admitted. The researchers found that the strains of bacteria in people with blood infections matched that of the probiotic medication. It isn’t yet clear whether the bugs are infecting patients through the gut or intravenous line contamination. For now, the researchers say when it comes to using probiotics in the ICU, the risks need to be weighed against the benefits.