Burrito chain Chipotle, which has endured a string of crises related to food-born illness, has engaged Rubenstein Associates for PR support.

chipotleThe Denver-based company has been reeling for months after outbreaks of norovirus and E. coli sparked a criminal probe of the company and decimated sales and its share price.

Chipotle recently split with Edelman after citing a client conflict with the industry's largest PR firm.

The chain shut down all of its restaurants on Monday to re-train its 50,000 employees in food safety procedures. In releasing its earnings on Feb. 2, co-CEO Steve Ells called the fourth quarter "the most challenging period in Chipotle's history."

A Centers for Disease Control and Prevention investigation has concluded, the company reported.

Fourth quarter revenue slipped 6.8% to $997.5M as sales were down 14.6% "due to publicity during the quarter surrounding food-borne illness incidents associated with a number of Chipotle restaurants."

Chipotle has 2,010 restaurants.