Human norovirus is a leading global cause of acute gastroenteritis and has no approved antiviral drug or vaccine, partly because the virus has been notoriously difficult to culture. A team in the Department of Food Science and Technology at the NUS Faculty of Science has identified a compound that interferes with infection: an exopolysaccharide, a sugar-based substance secreted by the probiotic bacterium Bacillus subtilis CU1.
The compound appears to work by binding the virus directly and preventing it from attaching to host cells. Crucially it contains no live microorganisms, which matters clinically because the populations most vulnerable to norovirus, older adults, young children and immunocompromised patients, are often advised against consuming live probiotics. It proved effective against the GII.4 strain responsible for most outbreaks worldwide.
The team also addressed production. They showed that the bacterium can ferment carrot juice to yield high levels of the compound while retaining its virus-blocking activity, suggesting a food-based rather than pharmaceutical delivery route. Their earlier zebrafish embryo model, developed in 2023, made it possible to grow and study the virus in the laboratory in the first place. The study was published in Food Microbiology.
The findings are laboratory-stage and further safety and efficacy work is needed before any preventive claim could be made. The approach is nonetheless notable for separating the benefit of a probiotic from the organism itself, a distinction that could matter across several conditions where live cultures are contraindicated but their metabolic products might not be.