For this batch, they put a baked potato in sealed, warm bottles and fermented it for several days- the perfect environment for producing botulism toxin. This prison brew (called pruno) is foul smelling and doesn't look much better either.
After the August cluster of cases, no special measures were taken to prevent botulism, the MMWR report says. After the second bunch of cases, the prison banned potatoes from the kitchen. There's talk about banning sugar and other sweets from the menu and the prison's store to curb pruno production, the report says.
But eliminating pruno won't be easy. "Pruno is widely used in correctional facilities throughout the country and is an ingrained part of prison culture," as the investigation of the Utah outbreak noted.
Education about the risks of botulism might help a little. But as long as there are incarcerated men with access to food rich in sugar or starch, pruno is likely to be on tap.