Chipotle tightening food safety after E. coli cases

Chipotle shares, which closed down 0.7 percent during the regular session, slid another 6.2 percent to $561.20 in extended trading.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center, said in an earlier interview that Chipotle’s limited menu may have made it more hard for investigators to detect the source of the outbreak.

The Centers for Disease Control and Prevention is investigating E. coli cases linked to Chipotle.

A Pennsylvania resident tested positive for the STEC O26 strain associated with the current outbreak of the illness that has sickened 52 people in nine states.

The agency said the most recent illness started on November 13.

The outbreak initially was reported in just Washington and OR, but has now spread to seven other states, including California, Illinois, Maryland, Minnesota, New York, Ohio and Pennsylvania.

Of the 52 people interviewed by CDC investigators, 47 reported eating at a Chipotle Mexican Grill restaurant before becoming sick, according to the CDC.

The ingredient responsible for the illnesses has not yet been determined. Two of the illnesses started in October, and five started in November 2015, suggesting that the outbreak was not as short lived as previously thought. Most infected people get diarrhea and abdominal cramps.

The company said it has been tightening its food safety procedures.

Chipotle said Friday that store closures and bad publicity linked to the outbreak have slammed its sales.

The company said sales trends so far in Q4 have been “extremely volatile”, and October comps were in the low-single-digit range.

“In testing for pathogens, in many ways you’re looking for needles in haystacks”. It also added that ingredients likely to have been connected to E. coli are no longer in Chipotle’s restaurants or supply system.

Chipotle spokesman Chris Arnold said in an email that “none of the ingredients that were in our restaurants at the time of this incident are still in our restaurants”. The company noted that its local produce program accounts for a “relatively small percentage” of the produce it uses, and only runs from around June through October in most parts of the country.