Chipotle founder Ells takes over as sole CEO at burrito chain

The company said at an investor conference last week that a food safety program it had put in place in the aftermath of the outbreaks had led to a drop in the quality of customer service. Chipotle's shares, which traded as high as $758.61 last August, have lost about 23 percent of their value since the start of the year, closing at $370 on Friday.