Source of E.coli outbreak linked to Chipotle investigated

Washington has reported 27 and Oregon 15 cases with 14 people being hospitalized (10 in Washington and (four in Oregon).

The Centers for Disease Control and Prevention (CDC) said 23 people were infected with Shiga toxin-producing E. coli O26 (STEC O26) that has the same DNA fingerprint.

It said it does not have any information to suggest that Chipotle Mexican Grill locations in other states are affected.

The investigation is ongoing to determine if the ill people ate a common meal item or ingredient that was served.

The US Food and Drug Administration (FDA) said it is working with others on laboratory analysis of foods sampled from the restaurants and is gathering information about the supply chain(s).

Chipotle Mexican Grill action​

Chipotle Mexican Grill has closed 43 restaurants in Oregon and Washington State even though only eight have drawn concern.

It said it is doing additional deep cleaning and full sanitization of its restaurants in the area, replacing all food items in the restaurants closed, batch testing some ingredients before resupplying, doing environmental testing in restaurants and food testing in restaurants and distribution centers.

The restaurant has also retained two consulting firms, one named as IEH Laboratories and Consulting Group, to help the company assess and improve upon standards for food safety.

Steve Ells, chairman and co-CEO of Chipotle, said it works with a number of fresh ingredients.

“If there are opportunities to do better, we will push ourselves to find them and enhance our already high standards for food safety. ​

“Our deepest sympathies go out to those who have been affected by this situation and it is our greatest priority to ensure the safety of all of the food we serve and maintain our customers’ confidence in eating at Chipotle.”​

Traceback methods​

Speaking about how the source will be identified, Dr Michael Doyle, Regents Professor of Food Microbiology, Director, Center for Food Safety, Department of Food Science & Technology, University of Georgia, said typically there are epidemiological studies using standard questionnaires to identify the vehicle.

“This involves case control studies that take into account the food consumption history of individuals who were affected and those that were not. If a food item is identified as having a statistically significant association with causing the illness, the investigation will focus on that that item.  ​

“Trace back techniques have gotten so good that it may be possible to trace the source of the contamination back to not only the processor but also the grower. ​

“The other thing that is new to this process and could help trace back is the use of whole genome sequencing of the outbreak bacteria for which the CDC and FDA are developing databases. ​

“For E. coli the complete genome information of outbreak strains is expected to be available in the next few years but the FDA and CDC may have enough information in their existing database to match the strain of ​E. coli​ to a particular source."​

Dr Chobi DebRoy, Clinical Professor, Department of Veterinary and Biomedical Sciences, Director, E. coli Reference Center, The Pennsylvania State University, said the FDA will isolate E. coli from produce and other food materials eaten and then identify the strain by established molecular methods.

“To determine the strain that may have caused the outbreak, E. coli​ isolated from victims of the outbreak and from the food consumed have to match genetically. If they match and show 98-100% identity statistically, they will be able to identify the source of the infection. DNA sequencing of the whole E. coli​ genomes have been also used for tracking sources of contamination by FDA. ​

"The molecular method generally takes at least 18- 24 hours just to isolate and confirm the bacterial strain as E. coli​. However, to determine the source it will take longer, since they have to test hundreds, if not thousands of samples, for the bacteria and compare the strains."​