The CDC spent three months hunting for whatever poisoned 60 Chipotle customers across 14 states in 2015. They tested the food, traced the suppliers, sequenced the bacteria's DNA. They never found it. That failure is the reason your barbacoa arrives in a vacuum-sealed bag. When investigators can't name the contaminated ingredient, you can't fix the ingredient. A Chipotle burrito mixes dozens of components that get chopped, cooked, and cross-contacted by hourly workers in over 2,000 kitchens.…