The secret of this stomach bug could save lives

For the first time, Australian scientists have narrowed in on the culprit behind a common type of food poisoning – a toxin secreted by the bacteria Bacillus cereus. This toxin can cause sickness even when the bacteria is no longer present in our food. Catching it in the act offers the possibility of treating the bug beyond the typical course of antibiotics, as medicine grapples with the growing problem of antibiotic resistance. Si Ming Man, who oversaw the research at the Australian National University, said food poisoning affected about four million Australians each year – and still caused millions of deaths globally – but developing new antibiotics was expensive and slow. “[Resistance] is becoming a major problem,” he said. “This is a breakthrough for us in looking at how [this bug] works and how we can treat it by blocking the toxin rather than just using antibiotics. It could save lives.” Food poisoning can be dangerous, particularly for people with compromised immune systems such as children, the elderly and pregnant women. If the bacteria escapes into the blood stream, it can trigger life-threatening conditions beyond the usual vomiting and diarrhoea such as sepsis, meningitis, and pneumonia. While the bacteria secretes a number of toxins, the ANU team were able to narrow in on the “nastiest customer” most responsible for illness, at least in its early stages. They developed tiny proteins to block the toxin from interacting with cells in the body. Lead researcher Anukriti Mathur said the study offered the first glimpse into how the toxin worked, meaning drug therapies could be developed to combat it. “We knew the toxin would have to attack the cells, triggering an immune reaction, but we didn’t know how it did it,” Ms Mathur said. “There was this beautiful moment in the lab where we captured [the bug] in action in real life, really close with the microscope, as the immune cell [sprang] into action to try to defend the body. The toxin actually binds to the cells and punches holes in them. So, we developed a molecule that binds to the toxin and restricts it.” A similar technology was also being developed in the US to treat a closely related bacteria that causes anthrax, Ms Mathur said. While Bacillus cereus is one of the most common stomach bugs, it is less widely known than household names like salmonella or listeria. “Before I started researching this, even I didn’t know about it but it’s in a lot of food, like rice and pasta, it’s in [meat] and vegetables,” Ms Mathur said. In 2013, a serious outbreak linked to the bug at a Canberra restaurant left 125 people ill. Prevention was the best defence, Dr Man said. He urged people to wash their hands before preparing food and to cook and re-heat meals properly to kill any existing bacteria and their toxins. Of course, researching food poisoning all day does encourage a certain interest in meal preparation, both scientists admit. “I have become a bit paranoid,” Dr Man laughed. “I’ve overcooked so much food.”

The Age, 11 December 2018 ;