Probiotics: sorting the evidence from the myths

To the Editor: We read Pham and colleagues’ recent article1 with interest, as evidence mounts against the use of probiotics in critically ill patients. Although a plausible and attractive theory, probiotics in the patient with acute illness now appear ineffective, if not positively harmful.

A recent randomised trial of probiotics in 298 patients with severe acute pancreatitis showed a non-significant rise in infective complications,2 in keeping with results of previous studies of critically ill patients.3,4 Disturbingly, mortality in the probiotic group was more than double that in the placebo group (P < 0.01). Bowel ischaemia was a prominent feature of deaths in the probiotic group (eight patients), but was not associated with any deaths in the placebo group (P < 0.004). It may be that non-occlusive mesenteric ischaemia in critical illness is exacerbated by the added bacterial load itself, or through a pro-inflammatory response by gut epithelial cells.

While probiotics may be a benign and beneficial adjunct to enteral feeding in certain clinical situations, there is persuasive evidence that probiotic therapy is associated with increased infective complications in critically ill patients and significant mortality in patients with severe acute pancreatitis. Until there is evidence to the contrary, we believe probiotics should not be administered to patients with severe acute illness.