This multi-center trial, spanning 26 Intensive Care Units (ICUs) in Australia and Canada and involving over 20,000 critically ill patients on mechanical ventilation, put a long-debated practice, Selective Decontamination of the Digestive Tract (SDD), to the test against standard care. The core question was whether aggressively targeting gut microbes would improve survival. Patients in the SDD group received a cocktail of oral and gastric antimicrobial interventions for the duration of ventilation, plus an initial four days of intravenous antibiotics.

ICUs were randomly assigned to use SDD or standard care over two 12-month periods.

Despite the intervention’s promise in theory, the ultimate finding for mortality was a bit of a damp squib: SDD did not result in a statistically significant lower incidence of in-hospital death by 90 days compared to standard care (27.9% mortality in the SDD group vs. 29.5% in the standard-care group).

While SDD didn’t move the needle on the primary and most critical outcome—saving lives—it did show a statistically significant benefit in reducing two types of critical infections. Specifically, the rate of new bloodstream infections was lower in the SDD group (4.9% vs. 6.8%).

More strikingly, the percentage of patients from whom antibiotic-resistant organisms were cultured was substantially lower with SDD (16.8% vs. 26.8%), representing a nearly 10-percentage-point difference.

So, while SDD appears to be effective at curbing the rates of certain hospital-acquired infections and antibiotic resistance, it simply wasn’t enough to translate into better overall survival for critically ill, mechanically ventilated patients. Given the effort and cost associated with SDD, the study’s conclusion suggests that the widespread adoption of this intervention as a life-saving measure is unwarranted based on the current evidence.

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