An outbreak of the deadly toxin Clostridium botulinum at a Utah prison last year was caused by a tainted batch of a prisoner-brewed alcoholic beverage called pruno, according to a report from the Centers for Disease Control and Prevention. The offending ingredient: a moldy baked potato added at the last minute.
Eight prisoners became seriously ill as a result of the brew, making it the largest botulism outbreak in the U.S. since 2007.
The beverage is usually made from fruit, sugar and water, which are fermented in plastic bags under cushions and piles of clothing to keep the temperature as high as possible. In the botulism-tainted batch, a prisoner had also added an old baked potato taken from the prison cafeteria.
CDC epidemiologists believe the toxin was produced when the potato, which sat at room temperature for several weeks, was added to the sealed plastic bag: The low-acidity, anaerobic environment is ideal for toxin growth, the investigators noted.